FORM 3CHEMISTRY
28/9/2006
Name_____________________________________________________________
What do you understand by:
a) Exothermic reaction.
- Heat produced along with the products and is lost to the surroundings as the system cools to attain room temperature
b) Heat of formation.
- Amount of heat absorbed or liberated when one mole of the substance is formed from its elements.
One mole of butane (C4H10) burns completely in oxygen and liberates 2877kJ.
a) Write the equation for the combustion of butane.
- C4H10 (g) + 13/2O2 (g) 4CO2(g) + 5H2O(l)
b) Draw an energy cycle diagram for these changes.
C4H10 (g) + 13/2O2 (g) 4CO2(g) + 5H2O(l)
4C(s) + 5H2(g)
c) If the following heats of combustion are given.
DHqc (graphite) = -393kJmol-1
DHqc (H2 (g)) = -286kJmol-1
DHqc (C4H10) = -2877kJmol-1
Calculate the heat of formation of butane, C4H10 from its elements in heir normal states at standard conditions of temperature and pressure.
DHfq(C4H10) = {DHqc (graphite) +D Hqc H2 (g)}- DHqc (C4H10)
= {(-393x4)+(-286x5)}-(-2877)
= -125kJmol-1
What is electrolysis?
- Decomposition of an electrolyte to allow passage of current.
b) The set up below represents electrolysis of dilute sulphuric (vi) acid.
Gas M
Gas N
Cathode
Anode
c) Name M and N.
M; Oxygen.
N; Hydrogen
d) Write ionic equations for
i) The production of gas M.
- 4OH-(aq) + 4e- O2 (g) + H2O (l)
j) The production of gas N.
- 2H+(aq) + 2e- H2 (g)
e) At what electrode does oxidation takes place? Explain your answer.
- Anode.
f) What type of electrodes is suitable for this experiment? Explain your answer.
- Platinum, Carbon.
- Un reactive
a) Give the oxidation number of Cr in the CrO42-
- Cr = +6
b) Give the change of oxidation number of the underlined species in the following
equations.
Cr2O72- + 8H+ + 3SO3 2- 2Cr3+ + 4H2O +3SO42-
- Cr = +6 to Cr = +3
c) Why are reactions like the above described as red ox reactions?
- Involves oxidation and reduction reactions.
Study the flow chart below and answer the questions that follow.
Gas Q carbon CO2
Brown gas R
Air heat
Gas T
a) Identify gas R and T.
- R = Nitrogen (iv) oxide.
- T = Nitrogen
b) State and explain the observations made when gas Q is bubbled through Iron (ii) sulphate solution
- It burns from green to dark brown because of the formation of the complex.
- FeSO4 (aq) +NO (g) FeSO4NO(aq)
Study the information in the table below and answer questions that follow (letters are not actual symbols of the elements)
Element
E.C of stable ion
Atomic radius
Ionic radius.
N
2.8.8
0.197
0.099
P
2.8.8
0.099
0181
R
2.8
0.160
0.065
S
2.8
0.186
0.095
T
2
0.152
0.068
U
2.8
0.072
0.136
i) Write the formula of the compound formed when N reacts with P [N=20,P=17].
- NP2
ii) Identify the elements, which belong to the third period of the periodic table. Explain.
- P, R, S
- They have a large/bigger atomic radius than ionic radius hence they lose electron to be stable thus in period 3.
iii) Which of the elements identified in (ii) above come first in the third period? Explain.
- R.
- Have smaller atomic radii than S.
iv) Select two elements, which are non-metals.
- P, U.
Magnesium hydroxide is used as a medication to relieve stomach acidity. Explain why sodium hydroxide is not used for the same purpose.
- Sodium hydroxide produces a lot of heat that may damage body tissues.
Study the diagram below
NaOH HCL Solution B
Zn2+ (aq) Solid A
NaOH Solution C
a) What property does solid A in the reactions above exhibit?
- Amphoterism.
b) Write the chemical reaction leading to the formation of solution C.
- Zn (OH) 2(g) +2OH-(aq) [Zn (OH) 4] 2-(aq)
Sunday, September 27, 2009
CHEM TEST
FORM 4 CHEMISTRY CAT
13TH JULY 2007
ANSWER ALL QUESTIONS IN THE SPACES PROVIDED
Dacron is a synthetic fibre formed by polymerization reaction between a dicarboxylic acid and a diol+ (an alcohol with two functional groups)
HOOC – C6H4 – COOH HO – (CH2) 2 – OH
a) Show how the polymerization occurs between the two
SOLUTION
HOOC – C6H4 – CO OH H O – (CH2) 2 – OH
H2O
HOOC – C6H4 – COO – (CH2) 2 – OH
b) Name the type of polymerization involved in forming Dacron
- Condensation polymerization
a) What is vulcanization of rubber?
- Heating rubber latex with sulphur.
b) State two properties that vulcanized rubber possess as a result of vulcanization.
- Rubber hardens.
- Greater tensile strength.
c) What property of concentrated sulphuric acid is illustrated by its action on
a. Sugar
- Dehydrating agent
b. Copper metal
- Oxidizing agent
c. Write a stoichometric equation for the reaction that occurs in (b) above
Cu(s) +2H2SO4(l) CuSO4 (aq) + SO2 (g) + 2H2O(l)
d) What determines the chemical properties of an organic compound?
- The functional groups e.g. double bond or triple bond
- OH-, COOH-
Chlorine gas was bubbled through water for sometime. The green-yellow solution formed was poured into a long glass tube as shown in the diagram below. Study the diagram and answer the questions that follow.
Sunlight
Q Long glass tube
Yellow green
a) Name the compounds formed in the green yellow solution
- HCL
- HOCL
b) Write a balanced equation for the formation of solution substance Q
2HOCL(aq) 2HCL(aq) + O2(g)
c) If the remaining solution was electrolyzed using graphite electrodes how would its PH change.
- The pH would rise due to removal of hydrogen ions
- 2H+ (aq) +2e- H2 (g)
In the contact process for the manufacture of sulphuric acid id represented as follows:
2SO2 (g) + O2 (g) 2SO3 (g) DH = -197Kjmol-1
a) If the reaction takes place in a closed vessel state one effect a catalyst has on the above reversible reaction.
- The equilibrium is reached more readily; it alters the rate at which the equilibrium is reached/attained.
b) What is the effect on the rate of the reaction above if
(i) Volume of the container is doubled?
- The reaction proceeds in the backward reaction due to reduced pressure i.e. SO3 breaks down into SO2 and O2.
(ii) Temperature is doubled?
- It is exothermic so temperature affects forward reaction equilibrium shifts to the left
5. a) What is a fuel?
- A substance that releases energy when burnt.
c) List two characteristics of a good fuel
- Heating value.
- Ease and rate of combustion.
- Availability.
- Ease of transportation
- Ease of storage.
- Environmental effects.
6. a) In terms of ions present distinguish between the following pairs of
Electrolytes.
i) Molten electrolyte and aqueous electrolyte
- Molten electrolyte; has only two types of ions
- Aqueous electrolyte; has additional ions of H+ and OH-
ii). Weak electrolyte and strong electrolyte
- Weak electrolyte; ionizes partially.
- Strong electrolyte; ionizes fully.
b) In terms of electrical energy distinguish between an electrolytic cell and an electrochemical cell.
- Electrolytic cell; system of converting chemical energy into electrical energy.
- Electrochemical cell; combination of two half-cells to give a full cell, which is capable of generating electric current from a redox reaction.
7. a) Oxide of Nitrogen contains a 30.4% nitrogen . Its density at s.t.p is 4.11gm-3. -------Determine the MF of the compound. (N=14, O=16 Molar gas Volume=22.4dm3)
SYMBOL N O
RAM 14 16
% MASS 30.4 69.6
MOLES 2.17 4.35
MOLE RATIO 1 2.0
Molecular mass of hydrogen gas = D X V = 4.11gdm-3 x 22 dm3
= 2.06g
EFM = 14 + (6 X 2) = 46
EF = NO2
EFM = 14 +32 = 46
MFM/EFM = n = 92.06/46 =2
MF = (NO2) 2 = N2O2
d) Magnesium ribbon was burned in a gas jar of Nitrogen. A few drops of water were then added to the solid formed in the jar. Write an equation for the second reaction.
Mg3N2 + 6H2O(l) 3Mg(OH)2 + 2NH3(g)
Prepared by
Akama B.N.
13TH JULY 2007
ANSWER ALL QUESTIONS IN THE SPACES PROVIDED
Dacron is a synthetic fibre formed by polymerization reaction between a dicarboxylic acid and a diol+ (an alcohol with two functional groups)
HOOC – C6H4 – COOH HO – (CH2) 2 – OH
a) Show how the polymerization occurs between the two
SOLUTION
HOOC – C6H4 – CO OH H O – (CH2) 2 – OH
H2O
HOOC – C6H4 – COO – (CH2) 2 – OH
b) Name the type of polymerization involved in forming Dacron
- Condensation polymerization
a) What is vulcanization of rubber?
- Heating rubber latex with sulphur.
b) State two properties that vulcanized rubber possess as a result of vulcanization.
- Rubber hardens.
- Greater tensile strength.
c) What property of concentrated sulphuric acid is illustrated by its action on
a. Sugar
- Dehydrating agent
b. Copper metal
- Oxidizing agent
c. Write a stoichometric equation for the reaction that occurs in (b) above
Cu(s) +2H2SO4(l) CuSO4 (aq) + SO2 (g) + 2H2O(l)
d) What determines the chemical properties of an organic compound?
- The functional groups e.g. double bond or triple bond
- OH-, COOH-
Chlorine gas was bubbled through water for sometime. The green-yellow solution formed was poured into a long glass tube as shown in the diagram below. Study the diagram and answer the questions that follow.
Sunlight
Q Long glass tube
Yellow green
a) Name the compounds formed in the green yellow solution
- HCL
- HOCL
b) Write a balanced equation for the formation of solution substance Q
2HOCL(aq) 2HCL(aq) + O2(g)
c) If the remaining solution was electrolyzed using graphite electrodes how would its PH change.
- The pH would rise due to removal of hydrogen ions
- 2H+ (aq) +2e- H2 (g)
In the contact process for the manufacture of sulphuric acid id represented as follows:
2SO2 (g) + O2 (g) 2SO3 (g) DH = -197Kjmol-1
a) If the reaction takes place in a closed vessel state one effect a catalyst has on the above reversible reaction.
- The equilibrium is reached more readily; it alters the rate at which the equilibrium is reached/attained.
b) What is the effect on the rate of the reaction above if
(i) Volume of the container is doubled?
- The reaction proceeds in the backward reaction due to reduced pressure i.e. SO3 breaks down into SO2 and O2.
(ii) Temperature is doubled?
- It is exothermic so temperature affects forward reaction equilibrium shifts to the left
5. a) What is a fuel?
- A substance that releases energy when burnt.
c) List two characteristics of a good fuel
- Heating value.
- Ease and rate of combustion.
- Availability.
- Ease of transportation
- Ease of storage.
- Environmental effects.
6. a) In terms of ions present distinguish between the following pairs of
Electrolytes.
i) Molten electrolyte and aqueous electrolyte
- Molten electrolyte; has only two types of ions
- Aqueous electrolyte; has additional ions of H+ and OH-
ii). Weak electrolyte and strong electrolyte
- Weak electrolyte; ionizes partially.
- Strong electrolyte; ionizes fully.
b) In terms of electrical energy distinguish between an electrolytic cell and an electrochemical cell.
- Electrolytic cell; system of converting chemical energy into electrical energy.
- Electrochemical cell; combination of two half-cells to give a full cell, which is capable of generating electric current from a redox reaction.
7. a) Oxide of Nitrogen contains a 30.4% nitrogen . Its density at s.t.p is 4.11gm-3. -------Determine the MF of the compound. (N=14, O=16 Molar gas Volume=22.4dm3)
SYMBOL N O
RAM 14 16
% MASS 30.4 69.6
MOLES 2.17 4.35
MOLE RATIO 1 2.0
Molecular mass of hydrogen gas = D X V = 4.11gdm-3 x 22 dm3
= 2.06g
EFM = 14 + (6 X 2) = 46
EF = NO2
EFM = 14 +32 = 46
MFM/EFM = n = 92.06/46 =2
MF = (NO2) 2 = N2O2
d) Magnesium ribbon was burned in a gas jar of Nitrogen. A few drops of water were then added to the solid formed in the jar. Write an equation for the second reaction.
Mg3N2 + 6H2O(l) 3Mg(OH)2 + 2NH3(g)
Prepared by
Akama B.N.
CHEM VII BRAIN TEASER
CHEMISTRY TESTLET
Name______________________________________________________
A compound, A which forms green crystals, dissolves in water to give a pale green solution. This solution gives a dirty green precipitate with sodium hydroxide solution and a white precipitate with dilute barium chloride solution acidified with dilute hydrochloric acid. When gently heated the solid A gives off water vapor (but no other gases) and forms a white powder B. When B is heated very strongly, it forms a red powder C and gives and gives off a gas that turns acidified potassium dichromate solution pale green C dissolves slowly in sulphuric acid to give a yellow solution D that forms a deep red coloration with potassium thiocyanate solution.
a) Which cation and which anion must a solution of A contain?
b) If B were dissolved in water would it form a colorless solution or pale green solution? Explain your answer
State two pieces of evidence to indicate that a reaction occurs when B is heated.
c) Solid C is found to be a metal oxide. Suggest a method that could be used to extract the metal from it.
d) Which cation must D contain?
e) The sequence of reactions from A and D must involve an oxidation process what is the evidence for this statement?
Some red crystals, known to contain the chloride anion and a metal cation (M2+), give off water vapor when gently heated, and turn blue. When dissolved in water, the crystals form a pink solution separate portions of this solution are tested as follows:
(i) Addition of dilute ammonia produces a blue precipitate that dissolves in an excess of ammonia to form a brownish yellow solution.
(ii) Addition of acidified hydrogen peroxide solution produces a black precipitate whose formula is shown to be M2O3
(iii) What else do you think the red crystals contain as well as chloride ions and M2+ ions?
Name______________________________________________________
A compound, A which forms green crystals, dissolves in water to give a pale green solution. This solution gives a dirty green precipitate with sodium hydroxide solution and a white precipitate with dilute barium chloride solution acidified with dilute hydrochloric acid. When gently heated the solid A gives off water vapor (but no other gases) and forms a white powder B. When B is heated very strongly, it forms a red powder C and gives and gives off a gas that turns acidified potassium dichromate solution pale green C dissolves slowly in sulphuric acid to give a yellow solution D that forms a deep red coloration with potassium thiocyanate solution.
a) Which cation and which anion must a solution of A contain?
b) If B were dissolved in water would it form a colorless solution or pale green solution? Explain your answer
State two pieces of evidence to indicate that a reaction occurs when B is heated.
c) Solid C is found to be a metal oxide. Suggest a method that could be used to extract the metal from it.
d) Which cation must D contain?
e) The sequence of reactions from A and D must involve an oxidation process what is the evidence for this statement?
Some red crystals, known to contain the chloride anion and a metal cation (M2+), give off water vapor when gently heated, and turn blue. When dissolved in water, the crystals form a pink solution separate portions of this solution are tested as follows:
(i) Addition of dilute ammonia produces a blue precipitate that dissolves in an excess of ammonia to form a brownish yellow solution.
(ii) Addition of acidified hydrogen peroxide solution produces a black precipitate whose formula is shown to be M2O3
(iii) What else do you think the red crystals contain as well as chloride ions and M2+ ions?
CHEM VI TESTLET
CHEMISTRY TESTLET
Name………………………………………………………………………….
State 3 uses of Nitrogen.
a) What do you understand by the term cracking in organic chemistry?
a) Mention two types of cracking
With the acid of a balanced equation describe what happens when concentrated sulphuric acid is added to copper (ii) sulphate crystals and sucrose
a) Copper (ii) sulphate
Observations; CuSO4,
Equation; Sucrose
Observations;
Equation;
From an experiment 20.0cm3 of hydrochloric acid required 25cm3 of 0.1M Na2CO3 solutions for complete reaction. Calculate the Molarity of the acid and its concentration in grams per liter.
i) Concentration in grams per liter
ii) Molarity of the acid
Explain why Magnesium continues to burn in Carbon (iv) Oxide. (Use equation)
What do you understand by the phrase ‘cloud seeding’
On heating 12.5g of a hydrated copper (ii) sulphate CuSO4.nH2O 8.0g of anhydrous copper (ii) sulphate remained. Find the formula of the hydrated salt.
Gas x was found to decolorize moist litmus paper but had no effect on dm litmus paper. A colorless solution of potassium bromide turned reddish-brown when the gas was bubbled through it.
a) Name gas x
b) State all the observations made when moist litmus paper is brought into contact with gas x
C (i) why did the colorless potassium bromide solution turn reddish-brown?
(ii) Write an equation for the reaction in c I above
(iii) From the equation in (ii) above state which of this reactant is
1. An oxidizing agent
2. A reducing agent
State four differences between carbon (iv) oxide and carbon (i) oxide.
Carbon (iv) oxide
Carbon (II) oxide
A white substance x when heated gave off carbon (IV). The residue was orange when hot, yellow when cold what was the substance x?
Use Graham’s law to calculate the relative rate of diffusion of ammonia and oxygen.
(H=1 N=14 O=16)
Ans 1.37.
Name………………………………………………………………………….
State 3 uses of Nitrogen.
a) What do you understand by the term cracking in organic chemistry?
a) Mention two types of cracking
With the acid of a balanced equation describe what happens when concentrated sulphuric acid is added to copper (ii) sulphate crystals and sucrose
a) Copper (ii) sulphate
Observations; CuSO4,
Equation; Sucrose
Observations;
Equation;
From an experiment 20.0cm3 of hydrochloric acid required 25cm3 of 0.1M Na2CO3 solutions for complete reaction. Calculate the Molarity of the acid and its concentration in grams per liter.
i) Concentration in grams per liter
ii) Molarity of the acid
Explain why Magnesium continues to burn in Carbon (iv) Oxide. (Use equation)
What do you understand by the phrase ‘cloud seeding’
On heating 12.5g of a hydrated copper (ii) sulphate CuSO4.nH2O 8.0g of anhydrous copper (ii) sulphate remained. Find the formula of the hydrated salt.
Gas x was found to decolorize moist litmus paper but had no effect on dm litmus paper. A colorless solution of potassium bromide turned reddish-brown when the gas was bubbled through it.
a) Name gas x
b) State all the observations made when moist litmus paper is brought into contact with gas x
C (i) why did the colorless potassium bromide solution turn reddish-brown?
(ii) Write an equation for the reaction in c I above
(iii) From the equation in (ii) above state which of this reactant is
1. An oxidizing agent
2. A reducing agent
State four differences between carbon (iv) oxide and carbon (i) oxide.
Carbon (iv) oxide
Carbon (II) oxide
A white substance x when heated gave off carbon (IV). The residue was orange when hot, yellow when cold what was the substance x?
Use Graham’s law to calculate the relative rate of diffusion of ammonia and oxygen.
(H=1 N=14 O=16)
Ans 1.37.
CHEM V METALS
SODIUM METAL
The diagram below shows the extraction of sodium metal using the Downs’ cell. Study it and answer the questions that follow;
NaCl in Gas
Molten sodium
Circular steel cathode
-ve
(-
(+ve)
Steel gauze cylinder
a) Explain why in this process the sodium chloride is mixed with calcium chloride.
- To lower melting point of sodium chloride from 800oC to 600oC hence reducing the cost of production of sodium.
b) Why is the anode made of graphite and not steel?
- Steel would react with chloride while graphite will not.
c) State two properties of sodium metal that make it possible for it to be collected as shown in the diagram
- Melting point lower than that of the electrolyte.
- Less dense than the electrolyte.
d) What is the function of the steel gauze cylinder?
- To prevent the chlorine and sodium from mixing/coming into contact.
e) Write an ionic equation for the reactions, which take place at the anode and cathode.
- I Cathode: - Na+(l) +e Na (l)
- II Anode: - 2Cl-(l) Cl2 (g) + 2e-
f) Give one industrial use of sodium and explain why it is stored under kerosene.
- Sodium vapor in street lamps
- Extraction of titanium.
- Manufacture of sodium peroxide.
- Make alloy with copper or lead.
Sodium is extracted by the electrolysis of fused sodium chloride.
- To free ions for easy discharge.
a) Why will fused sodium chloride conduct electricity but not solid sodium chloride?
- Have free ions.
b) The sodium chloride is mixed with a little calcium chloride flux and is made molten. Explain why.
- Lower melting point from 800oC to 600oC.
ZINC METAL
State two ores of Zinc metal.
- Zinc blende.
- Calamine (ZnCO3)
b) An ore is suspected to contain zinc as a constituent. Explain how presence of zinc can be confirmed.
- Add dilute nitric acid to the ore
- Filter
- To one portion add sodium hydroxide till excess, white precipitate formed, soluble in excess.
- To another portion add ammonia a white precipitate soluble in excess.
c) Name three substances that are used to concentrate an ore of zinc by froth-floatation.
- Oil
- Water
- Air
d) During the process of extraction of zinc metal the ores are first roasted in air to form metal oxides. Explain why this is important.
- The oxides are easier to reduce.
e) Zinc oxide is reduced by coke as shown by the equation below to form zinc metal and carbon monoxide.
ZnO(s) + C(s) Zn(s) + CO (g)
If 243 Kg of zinc oxide and 24Kg of coke were used, calculate the
Mass of zinc metal formed. [C=12, O=16 Zn= 65]
Mole of C = 24000/12 = 2000moles
Mole ratio Zn: C = 1:1 there for ZnO is in excess
Mass of Zn = 2000 x 65 = 130000g or 130 Kg
f) Study the set up below and answer the questions that follow.
Zinc
Gas X
Water
Heat
i) Explain the observations made the combustion tube.
- A white residue is formed
j) Write a balanced equation for the reaction in combustion tube.
- Zn(s) + H2O (g) ZnO(s) +H2 (g)
k) How would you test for gas X
- Introduce a burning splint in the gas jar full of X. It burns with a pop sound
l) State four uses of gas X in industries
- Manufacture of hydrochloric acid.
- Wielding, oxy-hydrogen flame (200oC) used in wielding.
- Manufacture of ammonia.
- Hardening of oils.
m) Identify two pollutants gases produced during the extraction of zinc metal.
- Carbon monoxide.
- Sulpur dioxide.
n) Explain how zinc is used in preventing rusting.
- By coating/galvanizing iron.
Study the flow chart below and answer the questions that follow.
Gas gas
ZnS O2 ZnO(s) Coke Zn(s)
Heat step 1 Step 2 Step 3
ZnSO4 (aq) + Water Gas D
a) State the conditions necessary for the reaction in step 2.
- Heat.
- High temperature.
b) Name gas D and three uses of Zinc.
- Sulphur dioxide
1. In batteries.
2. Galvanizing of iron Electroplating.
IRON METAL
An iron ore suspected to contain mainly iron. Describe a method that can be used to confirm the presence of iron in the ore.
- To the sample add sulphuric acid or hydrochloric acid and warm
- Filter the mixture
- To a portion of the filtrate add sodium hydroxide or ammonium hydroxide drop wise until in excess.
- Formation of dirty green precipate shows presence of iron II ions
Iron is extracted from its ore by the blast furnace process.
a) Name three ores from which iron is extracted.
- Haematite.
- Siderite.
- Magnetite.
a) One of the impurities in iron ore is removed in the form of calcium silicate. Write an equation for the reaction in which calcium silicate is produced.
CaO(s) + SiO2 (g) CaSiO3(l)
IRON ORE
Process R
SUBSTANCE A IRON (III) CHLORIDE SUBSTANCE B
BLAST FURNACE
The scheme above shows part of the extraction of iron from its ores. Study
It and answer the questions that follow
i) Name process R.
- Roasting or burning in air.
ii) Substances A and B are added to iron (iii) oxide below they are dropped into the blast furnace name A and B.
A = Coke
B = Limestone
iii) Briefly explain the functions of A and B.
- A Burns to form carbon (IV) oxide, which is reduced to carbon monoxide, which reduces the iron oxide to the metal.
- When heated decomposes to calcium oxide and carbon monoxide. The carbon dioxide is recycled and calcium oxide combines with acidic oxide to form slag.
iv) Iron obtained from the blast furnace is 90-95% pure. List two impurities present in raw iron.
- Carbon.
- Silicon.
- Manganese.
- Sulpur.
- Phosphorus.
Study the flow chart below and answer the questions that follow.
Light green Brown solid + Gas N + Gas P + 7moles of water
Solid K M
Dil. H2SO4
Fe (SO4) 3
b) Name substances; M, K, N, P.
- M; Iron (III) oxide.
- Iron (II) suphate.
- Sulphur trioxide.
- Sulphur dioxide.
c) Write a balanced equation for the reaction that took place when solid K was heated.
2FeSO4.7H2O(s) Fe2O3 +SO3+SO2+4H2O
Iron ore, coke, limestone and air are used in the blast furnace in the manufacture of iron. The reducing agent in the process is carbon monoxide.
a) Explain how the carbon monoxide is formed in the furnace.
C +O2 CO2
CO2 + C CO
b) Give the equation for the reaction in which iron is formed.
Fe2O3(s) +3CO (g) 2Fe (l) +3CO2 (g)
c) What is the importance of the limestone?
- Remove impurities.
- Generate carbon dioxide.
Give the role of slag formed during the manufacture of iron.
- Prevent re oxidation of iron.
List three uses of slag.
- Make fertilizers.
- Make cement.
- Building materials.
ALUMINIUM METAL
Study the flow chart below and answer the questions that follow.
Bauxite (Al2O3) with iron oxides
and silicates as impurities.
T
Solutions containing (Al (OH)-4 ions Residue
Precipitation and heating
Solid aluminium Oxide
Heat
Molten Aluminium oxide Electrolysis Molten Aluminium
Duralium alloy for aircraft parts frames Metal foil lining for food packets
i) Suggest a purpose for the industrial process represented by the flow chart.
- Extraction of aluminium, processing/refining of
ii) Explain how process T is carried out (equations not necessary)
- Bauxite is dissolved in sodium hydroxide, iron impurities ppt as iron (iii) hydroxide, then filtered off Carbon (IV) oxide is bubbled through aluminium hydroxide to ppt it.
iii) Explain why it is necessary to heat aluminium oxide before electrolysis is carried out.
- Make it molten (molten ore)
- Free the ions, Al3+ O2-
iv) What properties of aluminium and its alloy make them suitable for uses indicated? (At least five).
- Low density/light.
- Low tensile strength (can be stretched).
- Good conductor of heat.
- Not easily corroded by cooking because of un reactive coating of aluminium oxide.
- Reducing agent in thermite process.
The extraction of aluminium from its ore is two stages, purification stage and electrolysis stage. The melting point of aluminium oxide is 2054oC but electrolysis is carried out between 800-900oC.
a) Why is electrolysis not carried out at 2054oC?
- High temperature would facilitate the ignition or sparking of carbon electrodes. The carbon electrodes could burn at high temperatures. The fuel required to maintain high temperature is a lot hence expensive. The high temperatures could exceed the sublimation point of graphite.
b) What is done to lower the temperature?
- Adding cryolite or Na3AlF6
Aluminium chloride dissolves in water to form an acidic solution. Using equations explain how the acidic solution is formed.
- Aluminium chloride dissolves in water to form hydrated aluminium.
- AlCl3 +6H2O [Al (H2O) 6] 2+ +3Cl-
- The hydrated ion is hydrolyzed
- [Al (H2O) 6] 3+ +H2O [Al (H2O) 5 OH] 2+ + H3O+
The extraction of aluminium from its ores takes place in two stages, purification stage and electrolysis stage. The diagram below shows the set up for the electrolysis stage.
Anode
Electrolyte
i) Name the ore from which aluminium is extracted.
- Bauxite.
ii) Name one impurity, which is removed at the purification stage.
- Iron (II) oxide/Silicon (IV) oxide? Silica.
iii) Label the diagram each of the following
I) Anode.
II) Cathode.
III) Region containing electrolyte.
iv) The aluminium, which is produced, is tapped off as a liquid. What does this suggest about its melting point.
- The melting point is below 800oC.
The basic raw materials for extraction of aluminium are bauxite.
a) Name the method that is used to extract aluminium from bauxite.
- Electrolysis/hall/Heroult cell.
b) Write the chemical formulae of the major component of bauxite.
- Al2O3/Al2O3.H2O/Al2O3.2H2O.
c) Name the major impurities in bauxite.
- Iron (III) oxide, Fe2O3
- Silica, SiO2.
d) Explain how the impurities in bauxite are removed.
- Add hot concentrated sodium hydroxide/ potassium hydroxide, silica and aluminium oxide dissolve, filter iron (II) oxide.
- Bubble carbon (iv) oxide; add water and aluminium hydroxide to the filtrate to ppt aluminium hydroxide filter the aluminium hydroxide silicates remain in solution.
The diagram below shows the extraction of sodium metal using the Downs’ cell. Study it and answer the questions that follow;
NaCl in Gas
Molten sodium
Circular steel cathode
-ve
(-
(+ve)
Steel gauze cylinder
a) Explain why in this process the sodium chloride is mixed with calcium chloride.
- To lower melting point of sodium chloride from 800oC to 600oC hence reducing the cost of production of sodium.
b) Why is the anode made of graphite and not steel?
- Steel would react with chloride while graphite will not.
c) State two properties of sodium metal that make it possible for it to be collected as shown in the diagram
- Melting point lower than that of the electrolyte.
- Less dense than the electrolyte.
d) What is the function of the steel gauze cylinder?
- To prevent the chlorine and sodium from mixing/coming into contact.
e) Write an ionic equation for the reactions, which take place at the anode and cathode.
- I Cathode: - Na+(l) +e Na (l)
- II Anode: - 2Cl-(l) Cl2 (g) + 2e-
f) Give one industrial use of sodium and explain why it is stored under kerosene.
- Sodium vapor in street lamps
- Extraction of titanium.
- Manufacture of sodium peroxide.
- Make alloy with copper or lead.
Sodium is extracted by the electrolysis of fused sodium chloride.
- To free ions for easy discharge.
a) Why will fused sodium chloride conduct electricity but not solid sodium chloride?
- Have free ions.
b) The sodium chloride is mixed with a little calcium chloride flux and is made molten. Explain why.
- Lower melting point from 800oC to 600oC.
ZINC METAL
State two ores of Zinc metal.
- Zinc blende.
- Calamine (ZnCO3)
b) An ore is suspected to contain zinc as a constituent. Explain how presence of zinc can be confirmed.
- Add dilute nitric acid to the ore
- Filter
- To one portion add sodium hydroxide till excess, white precipitate formed, soluble in excess.
- To another portion add ammonia a white precipitate soluble in excess.
c) Name three substances that are used to concentrate an ore of zinc by froth-floatation.
- Oil
- Water
- Air
d) During the process of extraction of zinc metal the ores are first roasted in air to form metal oxides. Explain why this is important.
- The oxides are easier to reduce.
e) Zinc oxide is reduced by coke as shown by the equation below to form zinc metal and carbon monoxide.
ZnO(s) + C(s) Zn(s) + CO (g)
If 243 Kg of zinc oxide and 24Kg of coke were used, calculate the
Mass of zinc metal formed. [C=12, O=16 Zn= 65]
Mole of C = 24000/12 = 2000moles
Mole ratio Zn: C = 1:1 there for ZnO is in excess
Mass of Zn = 2000 x 65 = 130000g or 130 Kg
f) Study the set up below and answer the questions that follow.
Zinc
Gas X
Water
Heat
i) Explain the observations made the combustion tube.
- A white residue is formed
j) Write a balanced equation for the reaction in combustion tube.
- Zn(s) + H2O (g) ZnO(s) +H2 (g)
k) How would you test for gas X
- Introduce a burning splint in the gas jar full of X. It burns with a pop sound
l) State four uses of gas X in industries
- Manufacture of hydrochloric acid.
- Wielding, oxy-hydrogen flame (200oC) used in wielding.
- Manufacture of ammonia.
- Hardening of oils.
m) Identify two pollutants gases produced during the extraction of zinc metal.
- Carbon monoxide.
- Sulpur dioxide.
n) Explain how zinc is used in preventing rusting.
- By coating/galvanizing iron.
Study the flow chart below and answer the questions that follow.
Gas gas
ZnS O2 ZnO(s) Coke Zn(s)
Heat step 1 Step 2 Step 3
ZnSO4 (aq) + Water Gas D
a) State the conditions necessary for the reaction in step 2.
- Heat.
- High temperature.
b) Name gas D and three uses of Zinc.
- Sulphur dioxide
1. In batteries.
2. Galvanizing of iron Electroplating.
IRON METAL
An iron ore suspected to contain mainly iron. Describe a method that can be used to confirm the presence of iron in the ore.
- To the sample add sulphuric acid or hydrochloric acid and warm
- Filter the mixture
- To a portion of the filtrate add sodium hydroxide or ammonium hydroxide drop wise until in excess.
- Formation of dirty green precipate shows presence of iron II ions
Iron is extracted from its ore by the blast furnace process.
a) Name three ores from which iron is extracted.
- Haematite.
- Siderite.
- Magnetite.
a) One of the impurities in iron ore is removed in the form of calcium silicate. Write an equation for the reaction in which calcium silicate is produced.
CaO(s) + SiO2 (g) CaSiO3(l)
IRON ORE
Process R
SUBSTANCE A IRON (III) CHLORIDE SUBSTANCE B
BLAST FURNACE
The scheme above shows part of the extraction of iron from its ores. Study
It and answer the questions that follow
i) Name process R.
- Roasting or burning in air.
ii) Substances A and B are added to iron (iii) oxide below they are dropped into the blast furnace name A and B.
A = Coke
B = Limestone
iii) Briefly explain the functions of A and B.
- A Burns to form carbon (IV) oxide, which is reduced to carbon monoxide, which reduces the iron oxide to the metal.
- When heated decomposes to calcium oxide and carbon monoxide. The carbon dioxide is recycled and calcium oxide combines with acidic oxide to form slag.
iv) Iron obtained from the blast furnace is 90-95% pure. List two impurities present in raw iron.
- Carbon.
- Silicon.
- Manganese.
- Sulpur.
- Phosphorus.
Study the flow chart below and answer the questions that follow.
Light green Brown solid + Gas N + Gas P + 7moles of water
Solid K M
Dil. H2SO4
Fe (SO4) 3
b) Name substances; M, K, N, P.
- M; Iron (III) oxide.
- Iron (II) suphate.
- Sulphur trioxide.
- Sulphur dioxide.
c) Write a balanced equation for the reaction that took place when solid K was heated.
2FeSO4.7H2O(s) Fe2O3 +SO3+SO2+4H2O
Iron ore, coke, limestone and air are used in the blast furnace in the manufacture of iron. The reducing agent in the process is carbon monoxide.
a) Explain how the carbon monoxide is formed in the furnace.
C +O2 CO2
CO2 + C CO
b) Give the equation for the reaction in which iron is formed.
Fe2O3(s) +3CO (g) 2Fe (l) +3CO2 (g)
c) What is the importance of the limestone?
- Remove impurities.
- Generate carbon dioxide.
Give the role of slag formed during the manufacture of iron.
- Prevent re oxidation of iron.
List three uses of slag.
- Make fertilizers.
- Make cement.
- Building materials.
ALUMINIUM METAL
Study the flow chart below and answer the questions that follow.
Bauxite (Al2O3) with iron oxides
and silicates as impurities.
T
Solutions containing (Al (OH)-4 ions Residue
Precipitation and heating
Solid aluminium Oxide
Heat
Molten Aluminium oxide Electrolysis Molten Aluminium
Duralium alloy for aircraft parts frames Metal foil lining for food packets
i) Suggest a purpose for the industrial process represented by the flow chart.
- Extraction of aluminium, processing/refining of
ii) Explain how process T is carried out (equations not necessary)
- Bauxite is dissolved in sodium hydroxide, iron impurities ppt as iron (iii) hydroxide, then filtered off Carbon (IV) oxide is bubbled through aluminium hydroxide to ppt it.
iii) Explain why it is necessary to heat aluminium oxide before electrolysis is carried out.
- Make it molten (molten ore)
- Free the ions, Al3+ O2-
iv) What properties of aluminium and its alloy make them suitable for uses indicated? (At least five).
- Low density/light.
- Low tensile strength (can be stretched).
- Good conductor of heat.
- Not easily corroded by cooking because of un reactive coating of aluminium oxide.
- Reducing agent in thermite process.
The extraction of aluminium from its ore is two stages, purification stage and electrolysis stage. The melting point of aluminium oxide is 2054oC but electrolysis is carried out between 800-900oC.
a) Why is electrolysis not carried out at 2054oC?
- High temperature would facilitate the ignition or sparking of carbon electrodes. The carbon electrodes could burn at high temperatures. The fuel required to maintain high temperature is a lot hence expensive. The high temperatures could exceed the sublimation point of graphite.
b) What is done to lower the temperature?
- Adding cryolite or Na3AlF6
Aluminium chloride dissolves in water to form an acidic solution. Using equations explain how the acidic solution is formed.
- Aluminium chloride dissolves in water to form hydrated aluminium.
- AlCl3 +6H2O [Al (H2O) 6] 2+ +3Cl-
- The hydrated ion is hydrolyzed
- [Al (H2O) 6] 3+ +H2O [Al (H2O) 5 OH] 2+ + H3O+
The extraction of aluminium from its ores takes place in two stages, purification stage and electrolysis stage. The diagram below shows the set up for the electrolysis stage.
Anode
Electrolyte
i) Name the ore from which aluminium is extracted.
- Bauxite.
ii) Name one impurity, which is removed at the purification stage.
- Iron (II) oxide/Silicon (IV) oxide? Silica.
iii) Label the diagram each of the following
I) Anode.
II) Cathode.
III) Region containing electrolyte.
iv) The aluminium, which is produced, is tapped off as a liquid. What does this suggest about its melting point.
- The melting point is below 800oC.
The basic raw materials for extraction of aluminium are bauxite.
a) Name the method that is used to extract aluminium from bauxite.
- Electrolysis/hall/Heroult cell.
b) Write the chemical formulae of the major component of bauxite.
- Al2O3/Al2O3.H2O/Al2O3.2H2O.
c) Name the major impurities in bauxite.
- Iron (III) oxide, Fe2O3
- Silica, SiO2.
d) Explain how the impurities in bauxite are removed.
- Add hot concentrated sodium hydroxide/ potassium hydroxide, silica and aluminium oxide dissolve, filter iron (II) oxide.
- Bubble carbon (iv) oxide; add water and aluminium hydroxide to the filtrate to ppt aluminium hydroxide filter the aluminium hydroxide silicates remain in solution.
CHEM IV ORGANIC CHEMISTRY KCSE
ORGANIC CHEMISTRY
1. A compound Y reacts with bromine to form another compound whose formula is CH3CH2CHBrCHBrCH3. What is the formula and name of compound? 2MK [ P1, 1992]
Formula;
Name:
2. Part of the structure of the polymer, polyphenylethene is given below.
i) Draw the general structure of polyphenylethene. 1MK
ii) Draw the formula of the monomer from which it made.1MK
3. When p was mixed with ethanoic acid and a few drops of concentrated sulphuric acid added pleasant smelling liquid R was formed. P also reacted with sodium metal to produce gas s. (RMM of P=46).
i) To what class of compounds do the following belong? 1MK
P____________________ 1MK
R____________________ 1MK
ii) Name gas S__________________________ 1MK
iii) Write a possible structure of P IMK
iv) Write the equation of the reaction which produces gas S. IMK
v) Compound M and P belong to the same class of compounds; M has a relative formula mass of 102. Which of the compounds would be less soluble in water?
Explain. 2MK
vi) Complete the following equation 1MK [ P1, 1993]
CH3COOH + Na2CO3
4.
a) Write an equation to represent the polymerization of 1- chloropropene. [ 1 MK]
b) Name the polymer formed in (i) above. [1MK] [P1, 1993]
5.
a) Study the table below and answer the questions that follow
Formula of hydrocarbon
Boiling point K
C2H4
C3H6
C4H8
C5H10
C6H12
196.4
225.5
266.9
303.0
336.5
i) What is the name given to a series of organic compounds like the ones above? 1MK
ii) To what class of organic compounds like the ones above hydrocarbons belong? 1MK
iii) Select one of the hydrocarbons that would be a gas at room temperature (298K). Give a reason for your answer.2MK
iv) Give the formula of the seventh member of the above series. 1MK
v) What is the relationship between the boiling point and the RMM of the hydrocarbons in the above table? Explain your answer. 2MK
b) What would you observe if a few drops of potassium permanganate was reacted with any of the above hydrocarbons? Explain. 2MK
c) Study the flow chart below and answer the questions that follow.
Compound Z
Ethene
Alcohol X
H2SO4 (l) HCl
Heat, process Y
i) Write the formula of
Alcohol X; __________________________ 1MK
Compound Z; _________________ ______ 1MK
ii) Name process Y;______________________ 1MK [P1, 1993]
6. Propane and chlorine react as shown below.
CH3CH2CH3 + Cl2 CH3CH2CH2Cl + HCL
a) Name the type of reaction that takes place. 1MK
b) State the condition under which the reaction occurs.1MK [P1, 1994]
7. RCOO-Na+ and RC6H5SO3-Na represents two cleansing agents where R is a long hydrocarbon chain.
a) Write the formulae of the salts that would be formed when each of these cleansing agents is added to water containing calcium ions.1MK
b) Explain how the solubility of the two calcium salts affects the properties of the cleansing agents.2MK [ P1, 1994]
8. The general formula for a homologous series of organic compounds is CnH2n+1OH
a) Give the name and structure formula of the fourth member of this series. 2MK
b) Write an equation for the complete combustion of fourth member of this series. 1MK [P1, 1994]
9. In an experiment, soap solution was added to three separate samples of water. The table below shows the volume of soap solution required to form lather with 1000cc of each of the water samples before and after boiling.
Sample I
Sample II
Sample III
Volume of soap before water was boiled
27.0
3.0
10.6
Volume of soap after water was boiled
27.0
3.0
3.0
a) Which is likely to be soft?
Explain.2MK
b) Explain the change in the volume of soap solution used in sample III 1MK[P1, 1995]
10. Name one natural fibre. 1MK [ P1 1995]
11. Give one advantage of synthetic fibre over natural ones. 1MK [P1, 1995]
12. Study the table below and answer the questions that follow.
Alkane
Formula
Heat of combustion
Methane
Ethane
Propane
Butane
CH4
C2H6
C3H8
C4H10
-890
-1560
-2220
a)
b)
c)
a) Predict the heat of combustion of butane and write it on the space provided. 1MK
b) What do the sign of ∆Hc value indicate about combustion of alkanes?1MK [P1, 1995]
13. A compound C4H10O is oxidized by acidified potassium permanganate to form another compound C4H10O2. The same compound reacts with potassium to produce hydrogen gas.
a) Draw the structural formula and name compound C4H10O. 1MK
b) Write an equation for the reaction between potassium and compound C4H10O. 1MK [P1, 1995]
14. The table below gives information about the major constituent of crude oil. Study it and answer the questions that follow.
Constituent
Boiling point
Gases
Petrol
Kerosene
Diesel oil
Lubricating oil
Bitumen
Below 40
40-175
175-250
250-350
350-400
Above 400
i)
ii)
iii)
iv)
i) Which one of the constituent of crude oil has molecules with the highest number of carbon atoms? Explain. 2MK
ii) Name the process you would use to separate a mixture of petrol and diesel and explain how the separation takes place. 2MK
iii) Explain why the constituents of crude oil do not have a sharp boiling point.2MK
iv) Name one gas that is likely to be a constituent of crude oil and write its formula. 2MK
v) What condition would cause a poisonous to be formed when kerosene is burnt? Explain. 2MK [P1, B 1995]
15. The reaction of propane with chlorine gas gave a compound of formula C3H7Cl
a) What condition is necessary for the above reaction to take place? 1MK
b) Draw two structural formulae of the compound C3H7Cl.1MK [ P1, 1996]
16. Explain how a sample of CH3CH2CH2OH, could be distinguished from a sample of CH3COOH by means of a chemical reaction. 2MK [P1, 1996]
17. A compound whose structure is shown below is found in detergent. With reference to the structure explain how the detergent removes grease during washing. 2MK [P1, 1996]
18. A polymer has the following structure. A sample of this found to have a molecular mass of 5194. Determine the number of monomers in the polymer. 3MK [P1, 1996]
19. A mixture of pentane and pentanoic acid was shaken with 0.1M sodium hydroxide solution and let to separate as shown in the diagram below. Name the main layer W. Give a reason for your answer. 2MK [P1, 1996]
20.
a) Study the table below and answer the question that follow:
i) Which of the compound is solid at 10oC? Explain. 1MK
ii) Choose two compounds which are members of the same homologous series and explain the difference in their melting points.3MK
iii) The compound C3H8O is alcohol. How does the solubility in water differ from the solubility of C5H12? Explain. 2MK
b) Complete combustion of one mole of hydrocarbon produced four moles of carbon (iv) oxide and four moles of water only
i) Write the formula of the hydrocarbon 1MK
ii) Write the equation of the combustion reaction.1MK
c) In a reaction, an alcohol J was converted to Hex-1-ene.
i) Give the structure formula of the alcohol J 1MK
ii) Name the reagent and the condition necessary for the reaction in, c(i) above 1MK
Reagent; ______________________
Condition; _______________________
d) Compound K reacts with sodium hydroxide as shown below
HCOOH + NaOH HCOONa + H2O
i) What type of reaction is represented by the equation above? 1MK
ii) To what class of organic compounds does k belong?1MK [P1, 1996]
21. Complete the table below by inserting the missing information in the spaces provided
Name of polymer
Name of monomer
One use of the polymer
Polystyrene
Vinyl chloride
1.5MK [P1, 1997]
22. The structures shown below represent two cleansing agent A and B
A: R-COONa+ B: CH3 (CH2)11 - B- OSO3-Na+1.
Which cleansing agent would be more suitable for washing in water containing magnesium sulphate? Give a reason. 2MK [P1, 1997]
23. The empirical formula of a hydrocarbon is C2H3. The hydrocarbon has a molecular mass of 54.
a) Determine the molecular formula of the hydrocarbon.1MK
b) Draw the structural formula of the hydrocarbon.1MK
c) To which homologous series does the hydrocarbon belong?1MK [ P1, 1997]
24.
a) Give the names of the following compounds
i) CH3CH2CH2CH2OH;_______________________ 1MK
ii) CH3CH2COOH;___________________________1MK
iii) CH3COOCH2CH3; _________________________ 1MK
b) Study the information in the table below and answer the questions that follow
Number of carbon atoms per molecule
RMM of hydrocarbon
2
3
4
28
42
56
i) Write the general formula of the hydrocarbons in the table.1MK
ii) Predict the RMM of the hydrocarbon with 5 carbon atoms.1MK
iii) Determine the molecular formula of the hydrocarbon in (ii) above and draw its structural formula.2MK
c) Study the reaction scheme below and answer the questions that follow
i) Name the reagents used in:
Step I: ______________________________ 1MK
Step II: ______________________________1MK
Step IV: _____________________________1MK
ii) Write an equation for the complete combustion of ethyne. 1MK
iii) Explain one disadvantage of the continued use of items made from the compound in step III 1MK [ P1, B 1997]
25. Give one advantage and one disadvantage of petrol containing tetraethyl lead. 2MK [P1, 1998]
26. Draw the structural formula of
i) Ethanol [1MK]
ii) Propanoic acid[ 1MK]
iii) Give the name of the organic compound formed when ethanol and propanoic acid react in the presence of concentrated sulphuric acid.1MK [P1, 1998]
27. The formula given below represents a portion of a polymer. Give;
a) The name of the polymer.1MK
b) One disadvantage of continued use of this polymer.1MK [P1, 1998]
28. The column below was used to soften hard water.
i) Explain how the hard water was softened as it passes through the column. 1MK
ii) After some time the material in the column is not able to soften hard water. How can the material be activated? 1MK
iii) Give one advantage of using hard water for domestic purposes.1MK [P1, 1998]
29.
a) The following equations represent two different types of reactions
i) nC4H8(g) (C4H8)n(s)
ii) C2H6 (g) + Cl2 (g) C2H5Cl (l) + HCl
State the type of reaction represented by;
(i) ____________________________ 1MK
(ii) ____________________________ 1MK
b) The fermentation of glucose produces ethanol as shown in the equation below
C6H12O6 2CH3CH2OH + CO2.
The process produces about 10% ethanol by volume.
i) State how the concentration of ethanol produced could be increased. 1MK
ii) State and explain the observation that would be made if a piece of sodium metal; was added to a sample of ethanol in a beaker. 1MK
iii) Give two commercial uses of ethanol other than in the manufacture of alcoholic drinks. 2MK
c) The molecular formula of a hydrocarbon is C6H14. The hydrocarbon can be converted into two other hydrocarbons as shown in the equation below
C6H14 x + C3H6
i) Name and draw the possible structure of X. 1MK
ii) State and explain the observation that would be made is a few drops of bromine water was added to a sample of X. 1MK
iii) Write an equation for the complete combustion of C3H8.1MK [P 1, B 1998]
30. State the observations that would be made when a piece of sodium metal is placed in samples of; Pentane; 1MK
Pentanol; 1MK [P1, 1999]
31. State and explain one disadvantage of using hard water in a boiler. 2MK [P1, 1999]
32. Compound L reacts with hydrogen bromide to give another compound whose structure is CH3CH2CH2CHBrCH3.
Give the structural formula and name of compound L.
Write an equation for the reaction which takes place between ethyne and excess chlorine gas.2MK [P1, 1999]
33. One of the fuels associated with crude oil is natural gas. Name the main constituent of natural gas and write an equation for its complete combustion. 2MK [P1, 1999]
34. Bromine reacts with methane as shown below;
CH4 +Br2 CH3Br +HBr
a) What conditions are necessary for this reaction to occur?1MK
b) Identify the bonds which are broken and those that are formed.2MK [P1, 1999]
35.
a) When an organic compound Y reacted with aqueous sodium carbonate, it produces carbon (IV) oxide. Y reacts with propanol to form a sweet smelling compound Z whose formula is CH3CH2COOCH2CH2CH3. 1MK
i) Name and draw the structural formula of Y. 2MK
ii) What is the name of the group of compounds to which Z belong. IMK
b) In an experiment, excess ethanol was warmed with acidified potassium dichromate for about twenty minutes. State and explain the observation that was made at the end of the experiment. 2MK
c) The scheme below was used to prepare a cleansing agent. Study it and answer the questions that follow
Solution of cleansing agent
And an alcohol
Fat NaOH + Boil
Step I
Step II
Solid cleansing agent
i) What name is given to the type of cleansing agent prepared by the method shown in the scheme? 1MK
ii) Name one chemical substance added in step II. 1MK
iii) What is the purpose of adding the chemical substance named above?1MK
iv) Name one suitable substances that can be used in step I. 1MK
v) Explain how an aqueous solution of the cleansing agent removes oil from utensils during washing.2MK [P1, 1999]
36. In the presence of UV light, ethane gas undergoes substitution reaction with chlorine.
a) What is meant by the term substitution reaction? 1MK
b) Give the structural formula and name of the organic product when equal volumes of ethane and chlorine react together. 2MK [ P1, 2001]
37.
a) State one cause of temporary hardness of water.1MK
b) How does distillation remove water hardness?2MK [2001]
38.
a) In which homologous series do the following compounds belong?
i) CH3CCH;_________________ IMK
ii) CH3CH2COOH:_____________ 1MK
b) Raw rubber is heated with sulphur in the manufacture of natural rubber
i) What is the name given to the process? 1MK
ii) Why is the process necessary? 1MK
c) Study the scheme given below and answer the questions that follow
Propan-1-ol
Two products Potassium
I
A
Polymer C
Propene Br2/CCl4
II
Propane
Methane
Hydrocarbon
i) Write an equation for the reaction between propan-1-ol and potassium metal. 1MK
ii) Name the process I and II 2MK
I________________________ II_____________________________
iii) Identify the products A and B 2MK
iv) Name one catalyst used in process II 1MK
v) Draw the structural formula of the repeating unit in the polymer C. 1MK
d) State two industrial uses of methane. 2MK [P2, 2001]
THE MOLE
THE MOLE CONCEPT
1. 25CM3 of 0.1M sodium carbonate solution neutralized a solution containing 2.5g of sulphuric acid in 250cm3 of solution
a) Calculate the molarity of sulphuric acid and the volume of the acid used.
b) Write the equation for the reaction from this information.
2. 25.0cm3 of sodium hydroxide solution containing 1.0g of the alkali in 250cm3 of solution required 30.0cm3 of nitric acid for complete neutralization. Calculate the;
a) The molarity of the sodium hydroxide solution.
b) The molarity of the acid
3. A pupil analysed a commercial vinegar solution by titration and found that 24.5cm3 of 0.0981M sodium hydroxide solution was required for the titration of 1cm3 of vinegar. Calculate the molarity of ethanoic acid in vinegar. [Na = 23, H = 1, O = 16, N =14 ]
4. In a compound of magnesium and nitrogen, 54g of magnesium combines with 21g of nitrogen. Determine the empirical formula of the compound.
5. What mass of sodium oxide, Na2O could be formed from 3.45g of sodium. [ O = 16,Na = 23 ]
6. An evacuated flask has a mass of 90.050g. When filled with gas X at S.T.P. the flask weighs 90.121g. If the volume of the flask was 22.2cm3. Calculate the RMM of gas X and suggest its identity.
7. A concentrated solution of ammonia contains 30% of ammonia and has a density of 0.88gcm3. Calculate the molarity of ammonia solution.
8. 20 cm3 of 0.27M sodium hydroxide solution is added to 18.2 cm3 of 0.75M hydrochloric acid. To the solution is then added excess magnesium, what volume of hydrogen gas measured at S.T.P. evolved?
9. A metal hydroxide has the formula M (OH) 2. An aqueous solution of this hydroxide has a concentration of 6.16gl-1. 30cm3 of this solution requires 24cm3 of acid solution containing 5.67gl-1 of nitric acid for complete neutralization. Calculate;
a) The molarity of the metal hydroxide.
b) The relative atomic mass of the metal M
10. An aqueous solution of an acid contains 3.14g of XCOOH in 200cm3. 25cm3 of this acid solution are neutralized with 21.5cm3 of 0.207M solution of sodium hydroxide. Calculate the;
i) Formula mass of the acid.
ii) Relative mass of X in the acid.
11. 84cm3 of hydrogen chloride gas, measured at standard temperature and pressure is dissolved in water and titrated with 0.15M sodium hydroxide. What volume of sodium hydroxide solution is required for complete neutralization? What is the number of moles of hydrogen chloride.aka
12. 15cm3 of a solution containing 2.88gd-3 of an alkali solution XOH completely reacts with 20cm3 of 0.045M sulpuric acid. Calculate the molarity and R.A.M. of X present in the alkali.
13. 25.0 cm3 of an alkali MOH completely reacted with 20.0cm3 of nitric acid. The acid concentration was 6.3gdm-3 and that of the alkali was 3.2gdm-3. Calculate the molar mass of the alkali and hence the RAM of M.
1. 25CM3 of 0.1M sodium carbonate solution neutralized a solution containing 2.5g of sulphuric acid in 250cm3 of solution
a) Calculate the molarity of sulphuric acid and the volume of the acid used.
b) Write the equation for the reaction from this information.
2. 25.0cm3 of sodium hydroxide solution containing 1.0g of the alkali in 250cm3 of solution required 30.0cm3 of nitric acid for complete neutralization. Calculate the;
a) The molarity of the sodium hydroxide solution.
b) The molarity of the acid
3. A pupil analysed a commercial vinegar solution by titration and found that 24.5cm3 of 0.0981M sodium hydroxide solution was required for the titration of 1cm3 of vinegar. Calculate the molarity of ethanoic acid in vinegar. [Na = 23, H = 1, O = 16, N =14 ]
4. In a compound of magnesium and nitrogen, 54g of magnesium combines with 21g of nitrogen. Determine the empirical formula of the compound.
5. What mass of sodium oxide, Na2O could be formed from 3.45g of sodium. [ O = 16,Na = 23 ]
6. An evacuated flask has a mass of 90.050g. When filled with gas X at S.T.P. the flask weighs 90.121g. If the volume of the flask was 22.2cm3. Calculate the RMM of gas X and suggest its identity.
7. A concentrated solution of ammonia contains 30% of ammonia and has a density of 0.88gcm3. Calculate the molarity of ammonia solution.
8. 20 cm3 of 0.27M sodium hydroxide solution is added to 18.2 cm3 of 0.75M hydrochloric acid. To the solution is then added excess magnesium, what volume of hydrogen gas measured at S.T.P. evolved?
9. A metal hydroxide has the formula M (OH) 2. An aqueous solution of this hydroxide has a concentration of 6.16gl-1. 30cm3 of this solution requires 24cm3 of acid solution containing 5.67gl-1 of nitric acid for complete neutralization. Calculate;
a) The molarity of the metal hydroxide.
b) The relative atomic mass of the metal M
10. An aqueous solution of an acid contains 3.14g of XCOOH in 200cm3. 25cm3 of this acid solution are neutralized with 21.5cm3 of 0.207M solution of sodium hydroxide. Calculate the;
i) Formula mass of the acid.
ii) Relative mass of X in the acid.
11. 84cm3 of hydrogen chloride gas, measured at standard temperature and pressure is dissolved in water and titrated with 0.15M sodium hydroxide. What volume of sodium hydroxide solution is required for complete neutralization? What is the number of moles of hydrogen chloride.aka
12. 15cm3 of a solution containing 2.88gd-3 of an alkali solution XOH completely reacts with 20cm3 of 0.045M sulpuric acid. Calculate the molarity and R.A.M. of X present in the alkali.
13. 25.0 cm3 of an alkali MOH completely reacted with 20.0cm3 of nitric acid. The acid concentration was 6.3gdm-3 and that of the alkali was 3.2gdm-3. Calculate the molar mass of the alkali and hence the RAM of M.
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