Questions
INSTRUCTIONS TO CANDIDATES:
- Answer all the questions in the spaces provided.
- Mathematical tables and electronic calculators may be used.
- All working must be clearly shown where necessary.
- The grid below represents part of the periodic table. Study it and answer the questions that follow.
- Identity the family name to which element F and G belong. (1 mk)
- Name the type of bond formed when a and F belong. (1 mk)
- Write the formula of the oxide formed when D reacts with oxygen. (1 mk)
- What type of oxide is formed in (c) above. (1 mk)
- Compare the atomic radii of F and D. Explain. (2 mks)
- Element F burns in air to form two products. Write two equations of the two products formed. (3 mks)
- State two uses of element K and its compounds. (2 mks)
-
- Name the following organic compounds.
- CH3CH2CH(Br)CH3
- CH3-CH2CH2-CH2-C-O2H
- CH2CHCH2CH(Br)CH3
- Study the flow chart below and answer the questions that follow.
Name:-- The process that occur in steps marked I, II and IV. (1 mk)
- The reagent and conditions in step II. (1½ mks)
- Draw the structural formula of substance X, give the name of the substance. (2 mks)
- The diagram below shows a structure of a cleansing agent.
- Name the cleansing agent above. (1 mk)
- State the type of cleansing agent above. (1 mk)
- Name the material added to the cleansing agent in order to improve its cleansing property.
- Name the following organic compounds.
-
- 50cm3 of 1M copper (II) Sulphate solution was placed in a 100cm3 plastic beaker. The temperature of the solution was measured. Excess metal A powder was added to the solution, the mixture stirred and the maximum temperature was repeated using powder of metal B and C. The results obtained are given in the table below.
A B C Maximum temperature °C 2.63 31.7 22.0 Initial temperature (°C) 22.0 22.0 22.0 - Arrange the metal A, B, C and Copper in order of reactivity starting with the least reactive. Give reasons for the order. (3 marks)
- Other than temperature change, state one other observation that was made when the
- The Standard enthalpy change of formation of methanol is -239Kjmol-1
- Write the thermal chemical equation for the standard enthalpy change of formation of
- Use the following data to calculate the enthalpy change for the manufacture of methanol from carbon (II) oxide and hydrogen. (3 mks)
- CO(g) + ½ O2(g) CO2; ∆Hɵ = -283Kj/mol
H2(g) + ½ O2(g) H2O(l); = ∆Hɵ = -286Kj/mol
CH3OH + 32 CO2(g) + 2H2O; ∆Hɵ = -715Kj/mol
- CO(g) + ½ O2(g) CO2; ∆Hɵ = -283Kj/mol
- Study the information given in the table below and answer the questions that follow.
Bond Bond energy (Kjmol-1) C – H
Cl – Cl
C – Cl
H - Cl414
244
326
431
- 50cm3 of 1M copper (II) Sulphate solution was placed in a 100cm3 plastic beaker. The temperature of the solution was measured. Excess metal A powder was added to the solution, the mixture stirred and the maximum temperature was repeated using powder of metal B and C. The results obtained are given in the table below.
- Carbon IV oxide is produced when solid X is heated strongly. It can also be prepared by adding dilute hydrochloric acid to solid X. The reaction between X and dilute Sulphuric acid, however gradually slows down and stops.
-
- Name solid X. (1 mk)
- Write an ionic equation for the reaction of X and acid. (1 mk)
- A gas jar full of Carbon (IV) oxide was inverted over burning candle.
- State the observations made. (1 mk)
- What two properties of carbon (IV) oxide does this observation illustrate. (2 mks)
- Name a practical everyday use of this property of carbon (IV) oxide. (1 mk)
- The flow diagram below shows some reactions of calcium compounds.
- Name compound F and G. (2 mks)
- Write equations for reactions in step A, B and C. (3 mks)
-
-
- A piece of sodium metal which had been exposed to air, was found to be covered with a white powder. The piece was dropped into 50g of ethanol and 2400cm3 of hydrogen gas measured at room temperature and pressure was obtained. The unused ethanol was distilled off and a white solid remained (Na = 23, molar gas volume at room temperature and pressure = 24dm3)
- Name the other substance formed other than hydrogen. (1 mk)
- Calculate the mass of sodium that dissolved in ethanol. (2 mks)
- What mass of ethanol was distilled of assuming there was no loss during the process? (2 mks)
- The ethanol was distilled off at 80oC, while the white solid remained unaffected at this temperature. What is the difference in structure of ethanol and the white solid. (2 mks)
- Name another liquid which produces;
- Hydrogen with sodium metal. (1 mk)
- What difference would you observe if identical pieces of sodium were dropped
-
- Name the white powder coating the original piece of sodium, explain how it was formed. (3 mks)
- Describe one test by which you could identify white powder which originally covered
- A piece of sodium metal which had been exposed to air, was found to be covered with a white powder. The piece was dropped into 50g of ethanol and 2400cm3 of hydrogen gas measured at room temperature and pressure was obtained. The unused ethanol was distilled off and a white solid remained (Na = 23, molar gas volume at room temperature and pressure = 24dm3)
- The scheme below shows various reactions starting with hydrogen and nitrogen. Study it carefully and answer the questions that follow.
- Give one condition other than the of a catalyst that would favour the reaction in step I. (1 mk)
- Name the catalysts used in step I and II. (2 mks)
- Name substances P, Q, X and Y . (2 mks)
- Write equations for the reactions that takes kplace in step II. (3 mks)
- Name the oxidizing agent for the reaction that takes place in step IV. (1 mk)
- Why is a concentrated nitric acid transported on aluminium container and not copper? (1 mk)
- Use standard electric potentials for elements A, B, C, D and F given below to answer the questions that follow.
Eɵ (volts) A2+(aq) + 2e- ⇌ A(s)
B2+(aq) + 2e- ⇌B(s)
C+(aq) + 2e- ⇌ ½ C(g)
D2+(aq) + 2e- ⇌ D(s)
½ F2(g) + e- ⇌ F-(aq)-2.90
-2.38
-0.00
+0.34
+2.87- Which element is likely to be hydrogen? Give a reason for your answer. (2 mks)
- What is the Eɵ value of the strongest reducing. (1 mk)
- In the space provided, draw a labeled diagram of the electrochemical cell that would be obtained when half-cells of elements B and D are combined. (3 mks)
- Calculate the Eɵ value of the strongest reducing agent. (2 mks)
- During the electrolysis of aqueous copper II Sulphate using copper electrodes, al current of
- Write an ionic equation for the reaction that took place at the anode. (1 mk)
- Determine the change in mass of the anode which occurred as a result of the electrolysis process. (C.u = 63.5, 1 Faraday = 96,500 coulombs) (2 mks)
Marking Scheme
- The grid below represents part of the periodic table. Study it and answer the questions that follow.
- Identity the family name to which element F and G belong. (1 mk)
- Alkaline earth metals
- Name the type of bond formed when a and F belong. (1 mk)
- Ionic bond
- Write the formula of the oxide formed when D reacts with oxygen. (1 mk)
- D2O3
- What type of oxide is formed in (c) above. (1 mk)
- Amphoteric oxide
- Compare the atomic radii of F and D. Explain. (2 mks)
- Has a smaller atomic radius than F because D has more protons hence stronger nuclear attraction compared to F.
- Element F burns in air to form two products. Write two equations of the two products formed. (3 mks)
- 2F(s) + O2(g) → 2FO(s)
- 3F(s) + N2(g) → F3N2(s)
- State two uses of element K and its compounds. (2 mks)
- K cyanide is used in the extraction of gold
- Mixture of K and potassium is used as nuclear coolant.
- Identity the family name to which element F and G belong. (1 mk)
-
- Name the following organic compounds.
- CH3CH2CH(Br)CH3
-
- 2, 3 – dibromo – 2 - chloropentane
-
- CH3-CH2CH2-CH2-C-O2H
- Butanoic acid
- CH2CHCH2CH(Br)CH3
- 4 – bromopent-i-ene
- CH3CH2CH(Br)CH3
- Study the flow chart below and answer the questions that follow.
Name:-- The process that occur in steps marked I, II and IV. (1 mk)
- I – cracking
- II- Hydrogenation
- IV – Oxidation
- The reagent and conditions in step II. (1½ mks)
- Reagent – hydrogen
- Conditions – temp 150 – 250oC, nickel catalyst
- Draw the structural formula of substance X, give the name of the substance. (2 mks)
- The process that occur in steps marked I, II and IV. (1 mk)
- The diagram below shows a structure of a cleansing agent
- Name the cleansing agent above. (1 mk)
- Sodium alkylbenzene sulphonate
- State the type of cleansing agent above. (1 mk)
- Soapless detergent
- Name the material added to the cleansing agent in order to improve its cleansing property.
- Tetraoxophosphate materials
- Name the cleansing agent above. (1 mk)
- Name the following organic compounds.
-
- 50cm3 of 1M copper (II) Sulphate solution was placed in a 100cm3 plastic beaker. The temperature of the solution was measured. Excess metal A powder was added to the solution, the mixture stirred and the maximum temperature was repeated using powder of metal B and C. The results obtained are given in the table below.
- Arrange the metal A, B, C and Copper in order of reactivity starting with the least reactive. Give reasons for the order. (3 marks)
- C, Copper, A, B.
- B is the most reactive because it has highest ∆T.
- C is the least reactive because it cannot displace ions of copper from solution.
- A is more reactive than Copper because it displaces Cu2+ from solutions.
- Other than temperature change, state one other observation that was made when the most reactive metal was added to the copper (II) Sulphate solution. (1 mk)
- Blue colour of the solution fades /disappeared
- Black deposit is formed.
- Arrange the metal A, B, C and Copper in order of reactivity starting with the least reactive. Give reasons for the order. (3 marks)
- The Standard enthalpy change of formation of methanol is -239Kjmol-1
- Write the thermal chemical equation for the standard enthalpy change of formation of methanol. (1 mk)
- C(s) + 2H2(g) + ½ O2(g) → H3OH(g) ∆H= -239Kjg/mol
- Use the following data to calculate the enthalpy change for the manufacture of methanol from carbon (II) oxide and hydrogen. (3 mks)
- CO(g) + ½ O2(g) → CO2; ∆Hɵ = -283Kj/mol
H2(g) + ½ O2(g) → H2O(l); = ∆Hɵ = -286Kj/mol
CH3OH + 3/2 → CO2(g) + 2H2O; ∆Hɵ = -715Kj/mo -
∆HσCH3OH = ∆HcC + ∆HcH2 - ∆HcCH3OH
= -283 + 2(-286) – (-715)
= -283 – 576 + 715
= -859 + 715
∆Hf CH3OH = - 144Kj/mol
- CO(g) + ½ O2(g) → CO2; ∆Hɵ = -283Kj/mol
- Write the thermal chemical equation for the standard enthalpy change of formation of methanol. (1 mk)
- Study the information given in the table below and answer the questions that follow.
Calculate the enthalpy change for the reaction. (3 mks)-
Bond breaking energy – Bond formation energy
BBE - BFE
4(414) + 244 = 3 (414 + 326 + 431
(1900 – 1999) = -99Kj
= -99Kj
-
- 50cm3 of 1M copper (II) Sulphate solution was placed in a 100cm3 plastic beaker. The temperature of the solution was measured. Excess metal A powder was added to the solution, the mixture stirred and the maximum temperature was repeated using powder of metal B and C. The results obtained are given in the table below.
- Carbon IV oxide is produced when solid X is heated strongly. It can also be prepared by adding dilute hydrochloric acid to solid X. The reaction between X and dilute Sulphuric acid, however gradually slows down and stops.
-
- Name solid X. (1 mk)
- Calcium carbonate
- Write an ionic equation for the reaction of X and acid. (1 mk)
- CO32-(s) + 2H+(aq) → CO2(g) + H2O(l)
- Name solid X. (1 mk)
- A gas jar full of Carbon (IV) oxide was inverted over burning candle.
- State the observations made. (1 mk)
- Candle is immediately extinguished
- What two properties of carbon (IV) oxide does this observation illustrate. (2 mks)
- It does not support combustion and it is denser than air since it is poured downwards from gas jar.
- Name a practical everyday use of this property of carbon (IV) oxide. (1 mk)
- As a fire extinguisher
- State the observations made. (1 mk)
- The flow diagram below shows some reactions of calcium compounds.
- Name compound F and G. (2 mks)
- F = Calcium carbonate
G = Calcium hydroxide
- F = Calcium carbonate
- Write equations for reactions in step A, B and C. (3 mks)
- Step A: CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)
Step B: Ca(HCO3)2(aq) → CaCO3(s) + CO2(g) + H2O(l)
Step C: Ca(OH)2(g) → CaCO3(s) + H2O
- Step A: CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)
- Name compound F and G. (2 mks)
-
-
- A piece of sodium metal which had been exposed to air, was found to be covered with a white powder. The piece was dropped into 50g of ethanol and 2400cm3 of hydrogen gas measured at room temperature and pressure was obtained. The unused ethanol was distilled off and a white solid remained (Na = 23, molar gas volume at room temperature and pressure = 24dm3)
- Name the other substance formed other than hydrogen. (1 mk)
- Sodium ethoxide
- Calculate the mass of sodium that dissolved in ethanol. (2 mks)
- 2C2H5OH(l) + 2Na(s) → 2C2H5ONa(l) + H2(g)
2 moles Na gives 1 mole H2 at r.t.p.
46g Na gives 24.000cm3
2400cm3
2400cm3 x 46g
24000cm3 = 4.6g of sodium
- 2C2H5OH(l) + 2Na(s) → 2C2H5ONa(l) + H2(g)
- What mass of ethanol was distilled of assuming there was no loss during the process? (2 mks)
- 2 moles of C2H5OH 1 mole of H2 gas
(2 x 46)g C2H5OH gives 24000cm3
X 2400cm3
2 x 46 x 2400
2400 = 9.2g
Mass of distilled = (50g – 9.2g) = 40.8g
- 2 moles of C2H5OH 1 mole of H2 gas
- The ethanol was distilled off at 80°C, while the white solid remained unaffected at this temperature. What is the difference in structure of ethanol and the white solid. (2 mks)
- Ethanol is molecular structure with hydrogen bonds between molecules while white solid must be giant ionic structure with strong ionic bonds.
- Name the other substance formed other than hydrogen. (1 mk)
- Name another liquid which produces;
- Hydrogen with sodium metal. (1 mk)
- Water
- What difference would you observe if identical pieces of sodium were dropped separately into small beakers containing ethanol and this other liquid? (2 mks)
-
In ethanol In water Sinks, gas bubbles are formed Floats on surfaces, reacts vigorously and darts on surface producing a hissing sound.
-
- Hydrogen with sodium metal. (1 mk)
-
- Name the white powder coating the original piece of sodium, explain how it was formed. (3 mks)
- Sodium in air forms sodium oxide, which in presence of moisture forms sodium hydroxide, which reacts with carbon (iv) oxide in air to form sodium carbonate.
- Describe one test by which you could identify white powder which originally covered sodium. (2 mks)
- Add dilute HCl acid. Effervescence occurs and colourless gas is given off which forms a white precipitate in lime water.
- Name the white powder coating the original piece of sodium, explain how it was formed. (3 mks)
- A piece of sodium metal which had been exposed to air, was found to be covered with a white powder. The piece was dropped into 50g of ethanol and 2400cm3 of hydrogen gas measured at room temperature and pressure was obtained. The unused ethanol was distilled off and a white solid remained (Na = 23, molar gas volume at room temperature and pressure = 24dm3)
- The scheme below shows various reactions starting with hydrogen and nitrogen. Study it carefully and answer the questions that follow.
- Give one condition other than the of a catalyst that would favour the reaction in step I. (1 mk)
- High pressure
- Name the catalysts used in step I and II. (2 mks)
- Step I - finely divided iron
Step II – Vanadium V oxide/platinum
- Step I - finely divided iron
- Name substances P, Q, X and Y . (2 mks)
- P – ammonium sulplhate
Q – Copper metal
X – Oxygen
Y – nitrogen gas
- P – ammonium sulplhate
- Write equations for the reactions that takes kplace in step II. (3 mks)
- 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l)
2NO(s) + O2(g) → 2NO2
4NO2(g) + 2H2O(g) + O2(g) → HNO3(aq)
- 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l)
- Name the oxidizing agent for the reaction that takes place in step IV. (1 mk)
- Nitric acid
- Why is a concentrated nitric acid transported on aluminium container and not copper? (1 mk)
- Concentrated nitric acid with copper oxidizes it to Copper(II) nitrate, while aluminium forms layer of aluminium oxide which is a passive and stops any further action by the acid.
- Give one condition other than the of a catalyst that would favour the reaction in step I. (1 mk)
- Use standard electric potentials for elements A, B, C, D and F given below to answer the questions that follow.
- Which element is likely to be hydrogen? Give a reason for your answer. (2 mks)
- C+/C2 = hydrogen is used as the reference electrode
Eɵ value is 0.00/standard electrode potential
- C+/C2 = hydrogen is used as the reference electrode
- What is the Eɵ value of the strongest reducing. (1 mk)
- Eɵ = -2.90V
- In the space provided, draw a labeled diagram of the electrochemical cell that would be obtained when half-cells of elements B and D are combined. (3 mks)
- Calculate the Eɵ value of the strongest reducing agent. (2 mks)
- 2.38 + 0.34 = 2.72
0.34 –(-2.38) = +2.72
(0.34 + 2.38) = +2.72V
- 2.38 + 0.34 = 2.72
- During the electrolysis of aqueous copper II Sulphate using copper electrodes, al current of 0.2 amperes was passed through the cell for 5 hours.
- Write an ionic equation for the reaction that took place at the anode. (1 mk)
- Cu(s) → Cu2+(aq) + 2e-
or
Cu(s) → Cu2+(aq)
- Cu(s) → Cu2+(aq) + 2e-
- Determine the change in mass of the anode which occurred as a result of the electrolysis process. (C.u = 63.5, 1 Faraday = 96,500 coulombs) (2 mks)
- C = AI
(0.2 x 5 x 60 x 60)
0.2 x 5 x 60 x 60 x 63.5
2 x 96500
63 .5g Cu requires 2 x 96500
3600 C produces 63. 5 x 3600
2 x 96500
= 1.18gm
- C = AI
- Write an ionic equation for the reaction that took place at the anode. (1 mk)
- Which element is likely to be hydrogen? Give a reason for your answer. (2 mks)
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