Chemistry Paper 2 Questions and Answers - Moi Kabarak High School Mock 2020/2021

« Previous Topic
Chemistry Paper 1 Questions and Answers - Moi Kabarak High School Mock 2020/2021

Next Topic »
Chemistry Paper 3 Questions and Answers - Moi Kabarak High School Mock 2020/2021

Download PDF for future reference Get on Whatsapp for 50/-

Answer all the questions in the spaces provided
Mathematical tables and calculators may be used
ALL workings must be clearly shown where necessary

Study the data in the table below and answer the questions. The letters do not represent the actual symbols of the elements.

Element	Atomic number	Boiling point °C
P	3	1333
Q	13	2470
R	16	445
S	18	−186
T	19	774

Select the elements that belong to the same
1. Group (1 mk)
2. Period (1 mk)
Which element:
1. Is a gas at room temperature? Explain. (2 mks)
2. Does not take an oxide (1 mk)
Write the:
1. Formula of the Sulphate of element Q (1 mk)
2. Equation for the reaction between elements P and R (1 mk)
What type of bonding would exist in the compound formed when elements R and Q react? Give a reason for your answer. (2 mks)
Select the most electropositive element (1mk)
Explain why the boiling point of element Q is higher than that of element P. (2 mks)

In order to determine the imolar heat of neutralization of potassium hydroxide, 200cm³ of 1M Hydrochloric acid and 200cm³ Of IM Potassium hydroxide both at the same initial temperature were mixed and stirred continuously with a thermometer. The temperature of the resulting solution was recorded after every 30 seconds until the highest temperature of the solution was attained. Thereafter, the temperature of the solution was recorded for a further two minutes.
1. 1. Why was it necessary to stir the mixture of the two solutions? (1 mk)
  2. Define molar heat of neutralization (1 mk)
  3. Write an ionic equation for the reaction which took place (1 mk)
2. If the initial temperature for both solution was 24.5°C and the highest temperature attained by the mixture was 30.9°C.
  Calculate the:
  1. Heat change for the reaction (specific heat capacity of the solution
    = 4.2Jg⁻¹K⁻¹and the density of the solution = 1.0g/cm³ (2 mks)
  2. Molar heat at neutralization of potassium hydroxide. (2 mks)
3. Explain how the value of the molar heat of neutralization obtained in the experiment would compare with the one that would be obtained if the experiment was repeated using 200cm³ of 1 Mammonium hydroxide instead of IM potassium hydroxide. (2 mks)
4. Use the following information to answer the questions that follow:
  C_(s) + O_2(g) → CO_2(g)∆H = -393KJ/mol
  H_2(g) + ½O_2(g) → H₂0_(g)∆H = -296KJ/mol
  13
  C₄H₁₀+ ¹³/₂O_2(g) → 4CO_2(g)+ 5H₂0 ∆H =-2877K]moi
  Calculate the heat of formation of butane. (3 mrks)
Aqueous Copper (II) Sulphate was electrolyzed using the set up represented by the diagram below
1. After sometimes it was found that no gas was produced at both electrodes. Explain. (1 mk)
2. Write an equation for the reaction at each electrode. (2 mks)
  1. Anode
  2. Cathode
3. What happens to the colour of the electrolyte during electrolysis. Explain (2 mks)
4. An iron spoon is to be electroplated with silver. Draw a labeled diagram of the set-up that could be used to represent the process. (2 mks)
5. The following are half-cell equations for some elements. The letters do not represent actual symbols. Use the information to answer the questions that follow.
  Half cell E^θ, v
  M²⁺_(aq)+ 2ē → M_(s)+0.34
  L²⁺_(aq)+2ē → L_(s) +0.84
  K²⁺_(aq)+ 2ē → K_(s) -0.13
  J²⁺_(aq) + 2ē + J_(s)-0.76
  1. Select the two half cells that would produce the highest e.m.f of a cell. (1 mk)
  2. Calculate the e.m.f of the cell in d(i) above. (2 mks)
  3. Give the cell diagram notation for the cell in d(ii) above. (1 mk)

The scheme below shows several reactions starting with propanol. Study the scheme and answer the questions which follow.
reaction starting with propanol

Name gas R (1 mk)
Name and draw the structural formula of compound Q. (2 mk)
What conditions and reagents are necessary to convert S to CH₃CH₂COOCH₂CH₃ (2 mks)
Reagents Conditions
Write an equation for the reaction that takes place when equal volumes of chlorine gas react with propane. (1mk)

The table below shows some properties of organic compounds U, V and W. Use the information to answer the questions that follow.

	W	V	U
Reaction with liquid bromine	Decolourises bromine very fast	No reaction	Decolourises bromine liquid slowly
Combustion	Burns with yellow smoky flame	Burns with a blue flame leaving no residue	Burns with a yellow sooty flame
Reaction with Conc.H₂SO₄	No reaction	It is dehydrated to form compound U	Reacts to form V

To which homologous series do the compounds belong? (3 mks)
U-
V-
W-

CH₂ = CH – CH₃ when heated under high temperatures and pressures forms a solid with large molecular mass.
1. Write the equation for the reaction which involves the formation of the solid. (1 mk)
2. Name the solid and give one use of the solid (2 mks)

Study the flow chart below and answer the questions that follow
1. Identify gas:
  1. J..... (1mk)
  2. K... (1mk)
2. Write the equation for the reaction that occurs in steps:
  (V)........(1mk)
  (VI)... (1mk)
3. Name substance N.....(1mk)
4. Write an equation for formation of R and explain why high pressure is required in converting J to R (3 mks)
5. Give one commercial use of;
  1. Liquid T........(1mk)
  2. Compound Q....(1mk)
6. Describe a chemical test that would be used to distinguish the anion in compound Q and the product in Step IV (2 mks)
7. State and explain the observation made when concentrated sulphuric (VI) is added to crystals of copper (II) Sulphate in a beaker. (2 mks)
1. 1. Give the name of the reagent which when reacted with concentrated hydrochloric acid produce chlorine gas. (1 mk)
  2. A student out to prepare iron III chloride using the apparatus shown in the diagram below.
    1. Explain why:
      1. It is necessary to pass chlorine gas through the apparatus before heating begins. (1 mk)
      2. Calcium oxide would be preferred to calcium chloride in the guard tube. (1 mk)
    2. What property of iron (III) chloride makes it possible to be collected as shown in the diagram? (1mk)
    3. Write an equation form one chemical reaction that took place in the guard tube (1mk)
    4. The total mass of iron (III) chloride formed was found to be 0.5g.
      Calculate the volume of chlorine gas the reacted with iron.
      (Fe - = 56.0, C1 = 35.5 and Molar gas volume at 298K is 24,000cm³ (3 mk)
2. 1. Below is a graph that was obtained when different concentrations of hydrochloric acid was reacted with equal amount of calcium carbonate.
    
    The concentrations of hydrochloric acid were 0.8m, 0.5m and 0.1m. The calcium carbonate was in powder form. Match the graphs with concentrations.
    Graph I (1 mk)
    Graph II (1 mk)
  2. A state of equilibrium between dichromate (VI) and chromate ions is established as shown in the equation below.
    Cr₂O₇ _(aq) + 20H⁻_(aq) 2CrO_4(aq)+ H₂O_(l)
    Orange Yellow
    State and explain observation made when a few pellets of potassium hydroxide are added to the equilibrium mixture. (2 mks)
1. The above is a simplified diagram of the Downs Cell used for the manufacture of sodium. Study it and answer the questions that follow.
  1. What material is the anode made of? Give a reason (2 mks)
  2. What precaution is taken to prevent chlorine and sodium from re- combination? (1 mk)
  3. Write an ionic equation for the reaction in which chlorine gas is formed (1 mk)
2. In the Downs process, (used for manufacture of sodium), a certain salt is added to lower the melting point of sodium chloride from about 800°C to about 600°C.
  1. Name the salt that is added (1 mk)
  2. State why it is necessary to lower the temperature (1mk)
3. Explain why aqueous sodium chloride is not suitable as an electrolyte for the manufacture of sodium in the Downs process (2 mks)
4. Sodium metal reacts with air to form two oxides. Give the formulae of two oxides (1 mk)

Marking Scheme

Study the data in the table below and answer the questions. The letters do not represent the actual symbols of the elements.

Element	Atomic number	Boiling point °C
P	3 2.1	1333
Q	13 2.8.3	2470
R	16 2.8.6	445
S	18 2.8.8	−186
T	19 2.8.8.1	774

Select the elements that belong to the same
1. Group (1 mk)
  - P and T
2. Period (1 mk)
  - Q,R & S
Which element:
1. Is a gas at room temperature? Explain. (2 mks)
  - S, It's boiling point is below room temperature
2. Does not take an oxide (1 mk)
  - S
Write the:
1. Formula of the Sulphate of element Q (1 mk)
  - Q₂(SO₄)₃
2. Equation for the reaction between elements P and R (1 mk)
  - 2P_(s)+R_(s)→P₂R_(s)
What type of bonding would exist in the compound formed when eiements R and Q react? Give a reason for your answer.
(2 mks)
- Ionic
  Q transfers it's electrons to R when they react.
Select the most electropositive element (1mk)
- T
Explain why the boiling point of element Q is higher than that of element P. (2 mks)
- Q has strong metallic bond than P, it has more delocalised electrons hence strong metallic bond

In order to determine the inolar heat of neutralization of potassium hydroxide, 200cm³ of 1M Hydrochloric acid and 200cm³ Of IM Potassium hydroxide both at the same initial temperature were mixed and stirred continuously with a thermometer. The temperature of the resulting solution was recorded after every 30 seconds until the highest temperature of the solution was attained. Thereafter, the temperature of the solution was recorded for a further two minutes.
1. 1. Why was it necessary to stir the mixture of the two solutions? (1 mk)
    - To ensure heat is evenly distributed in the solution
  2. Define molar heat of neutralization (1 mk)
    - Enthalpy change when 1mole of a OH⁻are neutralized by 1mole of H⁺ to form 1 mole of water
  3. Write an ionic equation for the reaction which took place (1 mk)
    - OH⁻_(aq)+ H⁺_(aq)→H₂O_(l)
2. If the initial temperature for both solution was 24.5°C and the highest temperature attained by the mixture was 30.9°C.
  Calculate the:
  1. Heat change for the reaction (specific heat capacity of the solution
    = 4.2Jg⁻¹K⁻¹and the density of the solution = 1.0g/cm³) (2 mks)
    ∆H =400 × 4.2 × 6.4
    =10752J//10.75%
  2. Molar heat at neutralization of potassium hydroxide. (2 mks)
    Moles of KOH =200 × 1
    1000
    =0.2
    0.2→10.752
    1mole→?
    10.752 × 1
    0.2
    =−53.76KJ/mole
3. Explain how the value of the molar heat of neutralization obtained in the experiment would compare with the one that would be obtained if the experiment was repeated using 200cm³ of 1 Mammonium hydroxide instead of IM potassium hydroxide.
  (2 mks)
  - Ammonium hydroxide is a weak base, it's partially ionized some of the heat is used up to fully ionize. Heat of KOH is higher than ammonium hydroxide
4. Use the following information to answer the questions that follow:
  C_(s) + O_2(g) → CO_2(g)AH = -393KJ/mol
  H_2(g) + ½O_2(g) → H₂0_(g)AH = -296KJ/mol
  C₄H₁₀+ ¹³/₂O_2(g) → 4CO_2(g)+ 5H₂0 AH =-2877K]moi
  Calculate the heat of formation of butane. (3 mrks)
  
  ∆H=4x − 393 + 5x −296−−2877
  =−1572+−1480−−2877
  =−175KJ/mole
Aqueous Copper (II) Sulphate was electrolyzed using the set up represented by the diagram below
1. After sometimes it was found that no gas was produced at both electrodes. Explain. (1 mk)
  - At the cathode,Cu²⁺ are preferential discharged
  - At the anode Cu solid is discharged
2. Write an equation for the reaction at each electrode. (2 mks)
  1. Anode
    - Cu_(s) → Cu²⁺_(aq) + 2e⁻
  2. Cathode
    - Cu²⁺_(aq) + 2e⁻ → Cu_(s)
3. What happens to the colour of the electrolyte during electrolysis. Explain (2 mks)
  - Blue color remains blue Cu²⁺ removed are replaced by Cu dissolving at anode
4. An iron spoon is to be electroplated with silver. Draw a labeled diagram of the set-up that could be used to represent the process. (2 mks)
5. The following are half-cell equations for some elements. The letters do not represent actual symbols. Use the information to answer the questions that follow.
  Half cell E^θ, v
  M²⁺_(aq)+ 2ē → M_(s)+0.34
  L²⁺_(aq)+2ē → L_(s) +0.84
  K²⁺_(aq)+ 2ē → K_(s) -0.13
  J²⁺_(aq) + 2ē + J_(s)-0.76
  1. Select the two half cells that would produce the highest e.m.f of a cell. (1 mk)
    L_(s)/L²⁺_(aq), a-d J_(s)/J²⁺_(aq)
  2. Calculate the emf of the cell in d(i) above. (2 mks)
    +0.84−−a76 =+1.60v
  3. Give the cell diagram notation for the cell in d(ii) above. (1 mk)
    J_(s)/J²⁺_(aq)//L_(s)/L²⁺_(aq),E^θ=1.60v

The scheme below shows several reactions starting with propanol. Study the scheme and answer the questions which follow.

Name gas R (1 mk)
- Hydrogen
Name and draw the structural formula of compound Q. (2 mks)
Propene
What conditions and reagents are necessary to convert S to CH₃CH₂COOCH₂CH₃ (2 mks)
Reagents Ethanol Conditions 1. Drops of Conc. H2SO4 2. Warm
Write an equation for the reaction that takes place when equal volumes of chlorine gas react with propane. (1 mk)
CH₃CH₂CH_3(g) + Cl_2(g) → CH₃CH₂CH₂Cl +HCL

The table below shows some properties of organic compounds U, V and W. Use the information to answer the questions that follow.

	W	V	U
Reaction with liquid bromine	Decolourise bromine very fast	No reaction	Decolourises bromine liquid slowly
Combustion	Burns with yellow smoky flame	Burns with a blue flame leaving no residue	Burns with a yellow sooty flame
Reaction with Conc.H₂SO₄	No reaction	It is dehydrated to form compound U	Reacts to form V

To which homologous series do the compounds belong? (3 mks)
U-Alkene
V-Alkanol
W-Alkyne

CH₂ = CH – CH₃ when heated under high temperatures and pressures forms a solid with large molecular mass.
1. Write the equation for the reaction which involves the formation of the solid. (1 mk)
  n(CH₂=CHCH₃)→
2. Name the solid and give one use of the solid (2 mks)
  - Polypropene
    Making ropes,crates

Study the flow chart below and answer the questions that follow
1. Identify gas:
  1. J Sulphur (IV) Oxide (1mk)
  2. K Nitrogen(II)Oxide (1mk)
2. Write the equation for the reaction that occurs in steps:
  (V) NH₄NO₃(s)→ N₂O_(g)+ 2H₂O_(l)(1mk)
  (VI) SO_3(g) + H₂SO_4(l) → H₂S₂O_7(l) (1mk)
3. Name substance N Vanadium (VI) Oxide (1mk)
4. Write an equation for formation of R and explain why high pressure is required in converting J to R (3 mks)
  2SO_2(g)+O_2(g) → 2SO_3(g)Forward reaction leads to reduction in volume, high pressure is required to reduce the volume
5. Give one commercial use of;
  1. Liquid T Manufacture of fertilizer, Dyes, drugs, paints (1mk)
  2. Compound Q As a fertilizer (1mk)
6. Describe a chemical test that would be used to distinguish the anion in compound Q and the product in Step IV (2 mks)
  Product SO₄²⁻/NO₃⁻
  Chemical test; To each sample add barium Nitrate for SO₄²⁻a white preicpitate is formed for NO₃⁻,no white precipitate
7. State and explain the observation made when concentrated sulphuric (VI) is added to crystals of copper (II) Sulphate in a beaker. (2 mks)
  - Blue crystals changes to white powder
  - Conc H₂SO₄ dehydrates hydrated copper sulphate
1. 1. Give the name of the reagent which when reacted with concentrated hydrochloric acid produce chlorine gas. (1 mk)
    - Lead(IV)Oxide/ Manganese(IV)Oxide/Potassium Manganate(IV)
  2. A student out to prepare iron III chloride using the apparatus shown in the diagram below.
    1. Explain why:
      1. It is necessary to pass chlorine gas through the apparatus before heating begins. (1 mk)
        
        To prevent iron from being oxidized
      2. Calcium oxide would be preferred to calcium chloride in the guard tube. (1 mk)
        
        It also absorbs Cl₂, preventing it from escaping to the atmosphere.
    2. What property of iron (III) chloride makes it possible to be collected as shown in the diagram? (1 mk)
      - It sublimes when heated
    3. Write an equation form one chemical reaction that took place in the guard tube (1mk)
      Cl_2(g) +CaO_(s) → CaOCl_2(s)
    4. The total mass of iron (III) chloride formed was found to be 0.5g.
      Calculate the volume of chiorine gas the reacted with iron. (3 mk)
      (Fe - = 56.0, C1 = 35.5 and Molar gas volume at 298K is 24,000cm³
      2Fe_(s) + 3Cl_2(g)→ 2FeCl_3(s)
      Moles of FeCl₃ = ^0.5/_162.5
      =0.00308moles
      Mole ratio
      FeCl₃: Cl₂
      2:3
      0.00308 ?
      0.00308×³/₂
      0.00462 × 24000
      =110.88cm³
2. 1. Below is a graph that was obtained when different concentrations of hydrochloric acid was reacted with equal amount of calcium carbonate.
    The concentrations of hydrochloric acid were 0.8m, 0.5m and 0.1m. The calcium carbonate was in powder form. Match the graphs with concentrations.
    Graph I 0.8 (1 mk)
    Graph II 0.5 (1 mk)
  2. A state of equilibrium between dichromate (VI) and chromate ions is established as shown in the equation below.
    Cr₂O₇ _(aq) + 20H−_(aq) 2CrO_4(aq)+ H₂O_(l)
    Orange Yellow
    State and explain observation made when a few pellets of potassium hydroxide are added to the equilibrium mixture. (2 mks)
    - Mixture becomes yellow
    - KOH increases concentration of OH⁻ hence forward reaction is favoured
1. The above is a simplified diagram of the Downs Cell used for the manufacture of sodium. Study it and answer the questions that follow.
  1. What material is the anode made of? Give a reason (2 mks)
    - Graphite
      Does not react with products of electrolysis.
  2. What precaution is taken to prevent chlorine and sodium from re- combination? (1 mk)
    - Steel gauze diaphram is used to separate the Anode from cathode
  3. Write an ionic equation for the reaction in which chlorine gas is formed (1 mk)
    2Cl_(aq)→ Cl_2(g) + 2e⁻
2. In the Downs process, (used for manufacture of sodium), a certain salt is added to lower the melting point of sodium chloride from about 800°C to about 600°C.
  1. Name the salt that is added (1 mk)
    - Cryolite
  2. State why it is necessary to lower the temperature (1mk)
    - Reduce the amount of energy used hence lower cost
3. Explain why aqueous sodium chloride is not suitable as an electrolyte for the manufacture of sodium in the Downs process (2 mks)
  - H⁺ will be preferentially discharged hence H₂(g) will be produced instead of Na.
4. Sodium metal reacts with air to form two oxides. Give the formulae of two oxides (1 mk)
  Na₂O(s)/Na₂O₂