Chemistry P1 Questions and Answers - Momaliche 4 cycle Post Mock Exams 2021/2022

Share via Whatsapp

Instructions to Candidates

  1. Write your name and index number in the spaces provided above.
  2. Answer all the questions in the spaces provided.
  3. All working must be clearly shown.
  4. Non-programmable silent electronic calculators and KNEC mathematical tables may be used.

For Examiner’s Use only

Questions

Maximum score

Candidates score

1 - 27

80

 



QUESTIONS

    1. 120 cm3 of oxygen gas diffused through a porous partition in 50 seconds. How long would it take 80cm3 of Sulphur (IV) oxide to diffuse through the same partition under the same conditions? (S=32.0, 0=16.0) (3mks)
  1. The flow chart represents a series of reactions . Study it and answer the questions that follow.
    2 JHGAUYDGHA
    1. Identify substances G and J (2mks)
      G.........................................................
      J.............................................................
    2. Write a chemical equation for the formation of J. (1mk)
  2. At 20ºC, NO2 and N2O4 gases exist in equilibrium as shown in the equation below.
    3 javdya
    State and explain the observation that would be made when.
    1. The syringe containing the mixture is immersed in ice-cold water. (2mks)
    2. The volume in the gaseous mixture in the syringe is reduced. (2mks)
  3. A student suspected a given sample of water contains sulphate ions. Describe how he can show the presence of the sulphate ions in the water sample. (2mks)
  4. In the industrial manufacture of nitric (v) acid the first step is catalytic oxidation of ammonia gas.
    1. What is the name of the catalyst used. (1mk)
    2. Write the equation for the catalytic oxidation of ammonia gas. (1mk)
    3. State one use nitric acid. (1mk)
  5. Explain why boiling point of ethanol is higher than that of dimethylether. (Relative molecular mass of both of them is 46). (2mks)
  6. When 94.5g of hydrated barium hydroxide Ba(OH)2.n H2O were heated to a constant mass, 51.3g of anhydrous barium hydroxide were obtained. Determine the value of n.
    (Ba=137, O=16,H=1) (3mks)
  7. Study the diagram below and answer the questions that follow.
    8 utfaytda
    1. What do Δ H1 and Δ H2 represent (2mks)
      1. Δ H1
      2. Δ H2
    2. Give an expression for heat of solution in terms ofΔ H1, ΔH2 and Δ H3. (1mk)
  8. 6.84g of aluminium sulphate were dissolved in 300cm3 of water. Calculate the molar concentration of sulphate ions in the solution. (R.M.F=342) (3mks)
  9. Study the information given in the table below and answer the questions that follow.

    Bond

    Bond energy (KJ mol)

    C-H

    413

    Br-Br

    193

    C-Br

    280

    H-Br

    365

    1. Calculate the Enthalpy changes for the reaction below (2mks)
      CH4 (g) + Br2 (g) → CH3Br (g) + HBr (g)
    2. State whether the reaction is exothermic or endothermic. Explain (1mk)
  10. A certain mass of a metal E reacted with excess dilute hydrochloric acid at 250C. The volume of hydrogen gas liberated was measured after every 30 seconds. The results were represented as shown in the graph below. (1mk)
    11 ayfdaytfd
    1. Name one piece of apparatus that may be used to measure the volume of gas liberated. (1mk)
    2.                      
      1. On the same axis , sketch the curve that would be obtained if the experiment was repeated at 35ºC. (1mk)
      2. Explain the shape of your curve in b( i) above. (2mks)
  11.                          
    1. Why is hydrogen not readily used as a fuel? (1mk)
    2. State one uses of hydrogen gas. (1mk)
  12.                    
    1. State Charles’ Law. (1mk)
    2. A certain mass of a gas occupies 150cm3 at 281K and 109.41kPa. What will be its temperature if its volume is reduced by 16 cm3 at 101.325kPa. (2mks)
  13. 3g of iron reacted with hydrogen chloride gas at S.T.P. Calculate the volume of the hydrogen chloride gas used. (Fe=56, Molar gas volume at s.t.p=22.4dm3) (2mks)
  14. Under certain conditions , chlorine gas reacts with sodium hydroxide to form sodium hypochlorite.
    1. Name the conditions under which sodium hydroxide reacts with chlorine to form sodium hypochlorite. (1mk)
    2. State one use of sodium hypochlorite . (1mk)
  15.                      
    1. Distinguish between isotopes and allotropes (2mks)
    2. An element X has RAM of 69.39. Given that the element has two isotopes of masses 60.15 and 70.15. Calculate the relative abundance of each isotope (3mks)
  16. A student has a mixture of anhydrous aluminium chloride and zinc sulphate. Which is the simplest method of separation? (1mk)
  17. A student prepared ammonia and bubbled it into a solution of Magnesium sulphate as shown in the diagram below.
    1. Name any two reactants required for the production of ammonia. (1mk)
    2. State the observation in the beaker (1mk)
    3. Write ionic equation for the reaction in the beaker (1mk)
  18. The compound HCLO decomposes according to the following equation .
    5HClO(aq) → 2Cl2(g) + H+ (g) + ClO3- (aq)+ 2H2O(l)
    Deduce the oxidation states of chlorine in the following species.
    1. HClO (1mk)
    2. ClO3- (1mk)
  19. The set-up below was used to prepare dry sample of Oxygen gas
    1.                      
      1. Complete the diagram to show how the gas was collected (1mk)
      2. Identify the following
        1. Solid H....................................................................................................(1mk)
        2. Solid J...................................................................................................... (1mk)
    2. Write an equation for the reaction that occurred in the flask between solid H and water. .............. (1mk)
  20. The table below gives the solubility of salt L and K at 100C and 800C. Solubility in g/100g water
          Salt             At 10ºC          At 80ºC
           L                 60                   75
           K                 20                   32
    When an aqueous mixture containing 80g of L and 10g of K in 100g water at 80ºC was cooled to 10ºC,crystallization occurred.
    1. What is crystallization (1mk)
    2. Determine the mass of the crystals formed (1mk)
    3. Name the method of separation (1mk)
  21. The table below gives elements represented by letters T,U,V,W,X,Y and their atomic numbers . (Letters are not the actual symbols.

    Element

    T

    U

    V

    W

    X

    V

    Atomic number

    12

    13

    14

    15

    16

    17

    1.                           
      1. How does the atomic radius of V compare with that of X? Explain. (2mks)
      2. Give the formula of the compound that could be formed between U and X. (1mk)
    2.                          
      1. Arrange the species T,T- and T+ in increasing order of size. (1mk)
      2. Which of the ions X2+ and X2- is the most stable ? Explain. (2mks)
  22.                                
    1. What would be observed in sulphur IV Oxide is bubbled through acidified potassium. chromate VI (1mk)
    2. In an experiment, sulphur (IV) Oxide was dissolved in water to form solution M.
      1. State the observation made if a few drops of barium chloride solution immediately added to solution M (1mk)
      2. Identify the spectator ions from the reaction b(i) above (1mk)
  23. Copper-64 has a half life of 12.8days.
    1. What is meant by the term half life (1mk)
    2. What mass of a copper-64 will be left after 51.2 days starting with 20 g of the isotopes (2mks)
    3. Give one use of radioactive isotopes in medicine (1mk)
  24.                              
    1. Zeolites (Na2X) is a complex compound used to soften hard water in the ion-exchange methods according to the equation below.
      Ca 2+ (aq) +Na2X (aq) → CaX(s) + 2Na+ (aq)
      After sometimes the Zeolites get exhausted and ceases to soften water. Write a reaction to show how Zeolite is regenarated. (1mk)
  25. Name the particle responsible for electrical conductivity on;
    1. Molten magnesium metal (1mk)
    2. Molten magnesium chloride (1mk)
  26. Carbon is one of the elements that exhibit allotropy
    1. Define the term allotrophy (1mk)
    2. Name two allotropes of carbon (1mk)
    3. Which allotrope of carbon is a good conductor of electricity. Explain. (2mks)


MARKING SCHEME

  1. 120 cm3 of oxygen gas diffused through a porous partition in 50 seconds. How long would it take 80cm3 of Sulphur (IV) oxide to diffuse through the same partition under the same conditions? (S=32.0, 0=16.0) (3mks)
    RO2 = 120 = 24 cm3/sec
                50
    O2 = 32
    SO2 = 64
       2.4    = √64
    RSO2       32
    RSO2 = 1.697cm3/sec
    1.697 = 80cm3
                  t
    t = 47.14 sec
  2. The flow chart represents a series of reactions . Study it and answer the questions that follow.
    2 JHGAUYDGHA
    1. Identify substances G and J (2mks)
      G.......sodium hydroxide
      J........methane
    2. Write a chemical equation for the formation of J. (1mk)
      CH3COONa(s) + NaOH(aq) → CH4 (g) + Na2CO3(s)
  3. At 20ºC, NO2 and N2O4 gases exist in equilibrium as shown in the equation below.
    3 javdya
    State and explain the observation that would be made when.
    1. The syringe containing the mixture is immersed in ice-cold water. (2mks)
      forward reaction is favoured because it is pale yellow colour intensifies as the brown color fades
    2. The volume in the gaseous mixture in the syringe is reduced. (2mks)
      foward reaction is favoured  because pale yellow colour intensifies as brown color fades
  4. A student suspected a given sample of water contains sulphate ions. Describe how he can show the presence of the sulphate ions in the water sample. (2mks)
    to the sample add 2/3 drops of acidified Ba(NO3)2 / BaCl2 solution
    a white ppt is formed
  5. In the industrial manufacture of nitric (v) acid the first step is catalytic oxidation of ammonia gas.
    1. What is the name of the catalyst used. (1mk)
      platinum / platinum - rhodium
    2. Write the equation for the catalytic oxidation of ammonia gas. (1mk)
      4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l)
    3. State one use nitric acid. (1mk)
      manufacture of nitrogenous fertilizer / explosives / dyes purification of metals / etching designs on metals
  6. Explain why boiling point of ethanol is higher than that of dimethylether. (Relative molecular mass of both of them is 46). (2mks)
    molecules of ethanol are held by hydrogen bonds that are stronger than van der waals that hold molecules of dimethyether
  7. When 94.5g of hydrated barium hydroxide Ba(OH)2.n H2O were heated to a constant mass, 51.3g of anhydrous barium hydroxide were obtained. Determine the value of n.
    (Ba=137, O=16,H=1) (3mks)
    compound  Ba(OH)2  H2
     mass  51.3  43.2
     R.F.M  171  18
     no.of .moles  0.3  2.4
     mole ratio  1  8
    n = 8
  8. Study the diagram below and answer the questions that follow.
    8 ajgduyag ans
    1. What do Δ H1 and Δ H2 represent (2mks)
      1. Δ Hlattice energy
      2. Δ Hhydration energy
    2. Give an expression for heat of solution in terms ofΔ H1, ΔH2 and Δ H3. (1mk)
      Δ H3 = Δ H1 + Δ H2
  9. 6.84g of aluminium sulphate were dissolved in 300cm3 of water. Calculate the molar concentration of sulphate ions in the solution. (R.M.F=342) (3mks)
    Al2(SO4)3 → 2AL3+(aq) + 3SO42-(aq)
    6.84 = 0.02
    342
    Al2(SO4)3 : SO42-
                  1:3
            0.02 : 0.06
    1000 × 0.06
     300
    = 0.2M
  10. Study the information given in the table below and answer the questions that follow.

    Bond

    Bond energy (KJ mol)

    C-H

    413

    Br-Br

    193

    C-Br

    280

    H-Br

    365

    1. Calculate the Enthalpy changes for the reaction below (2mks)
      CH4 (g) + Br2 (g) → CH3Br (g) + HBr (g)
      B.B  B.F 
      (4 × 413) + 193 (3 × 413) + 280 + 365
       - + 1845  - - 1884
      (+ 1845) + (- 1884)
      = -39 kJmol-
    2. State whether the reaction is exothermic or endothermic. Explain (1mk)
      exothermic - bond formation energy is higher than bond breakage energy
  11. A certain mass of a metal E reacted with excess dilute hydrochloric acid at 250C. The volume of hydrogen gas liberated was measured after every 30 seconds. The results were represented as shown in the graph below. (1mk)
    11 agdyua ss
    1. Name one piece of apparatus that may be used to measure the volume of gas liberated. (1mk)
      graduated gas syringe
      graduated gas jar
    2.                      
      1. On the same axis , sketch the curve that would be obtained if the experiment was repeated at 35ºC. (1mk)
      2. Explain the shape of your curve in b( i) above. (2mks)
        increase in temp, increases the kinetic energy. This increases the number of effective collisions per given time, resulting in increase in rate of reaction
  12.                          
    1. Why is hydrogen not readily used as a fuel? (1mk)
      it's explosive when mixed with air and ignited
    2. State one uses of hydrogen gas. (1mk)
      manufacture of NH3/HCl
      hardening of oils
      rocket fuel
  13.                    
    1. State Charles’ Law. (1mk)
      the volume of a given fixed mass of gas is directly proportional to its absoulute temperature at constant pressure
    2. A certain mass of a gas occupies 150cm3 at 281K and 109.41kPa. What will be its temperature if its volume is reduced by 16 cm3 at 101.325kPa. (2mks)
      281 × 134 × 101.325 k pa = 232.5 k
      150 × 109.41 k pa
  14. 3g of iron reacted with hydrogen chloride gas at S.T.P. Calculate the volume of the hydrogen chloride gas used. (Fe=56, Molar gas volume at s.t.p=22.4dm3) (2mks)
    Fe(s) + 2HCl(g) → FeCl2(s) + H2(g)
    3/56 = 0.0534 moles
    fe:Hcl
    1:2
    0.0534:0.1068
    0.1068 × 22.4dm3
    =2.39dm3
  15. Under certain conditions , chlorine gas reacts with sodium hydroxide to form sodium hypochlorite.
    1. Name the conditions under which sodium hydroxide reacts with chlorine to form sodium hypochlorite. (1mk)
      dilute NaOH
      cold NaOH
    2. State one use of sodium hypochlorite . (1mk)
      used for water purification
      bleaching agent
  16.                      
    1. Distinguish between isotopes and allotropes (2mks)
      isotopes - atoms of some element with the same proton number but different neuron no.
      allotropes - different forms of an element in the same physical state
    2. An element X has RAM of 69.39. Given that the element has two isotopes of masses 60.15 and 70.15. Calculate the relative abundance of each isotope (3mks)
      69.39 = (x × 60.15) + ((100 - x) × 70.15)
                               100
      x = 7.6%
      100 - x = 92.4%
  17. A student has a mixture of anhydrous aluminium chloride and zinc sulphate. Which is the simplest method of separation? (1mk)
    sublimation
  18. A student prepared ammonia and bubbled it into a solution of Magnesium sulphate as shown in the diagram below.
    18 auyguyad
    1. Name any two reactants required for the production of ammonia. (1mk)
      calcium hydroxide
      ammonium chloride
      any ammonium salt and alkali
    2. State the observation in the beaker (1mk)
      white ppt formed
    3. Write ionic equation for the reaction in the beaker (1mk)
      Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s)
  19. The compound HCLO decomposes according to the following equation .
    5HClO(aq) → 2Cl2(g) + H+ (g) + ClO3- (aq)+ 2H2O(l)
    Deduce the oxidation states of chlorine in the following species.
    1. HClO (1mk)
      (+1) + cl + (-2) = 0
      cl = +1
    2. ClO3- (1mk)
      cl + 3(-2) = -1
      cl = +5
  20. The set-up below was used to prepare dry sample of Oxygen gas
    20 aigdya
    1.                      
      1. Complete the diagram to show how the gas was collected (1mk)
      2. Identify the following
        1. Solid H..........sodium peroxide......(1mk)
        2. Solid J...........anhydrous CaCl2........ (1mk)
    2. Write an equation for the reaction that occurred in the flask between solid H and water. .............. (1mk)
      2Na2O2(s) + 2H2O(l) → 4NaOH(aq) + O2(g)
  21. The table below gives the solubility of salt L and K at 100C and 800C. Solubility in g/100g water
          Salt             At 10ºC          At 80ºC
           L                 60                   75
           K                 20                   32
    When an aqueous mixture containing 80g of L and 10g of K in 100g water at 80ºC was cooled to 10ºC,crystallization occurred.
    1. What is crystallization (1mk)
      process of allowing saturated solutions to cool for crystals to form
    2. Determine the mass of the crystals formed (1mk)
      75 - 60 = 15 + 5 = 20g
      80 - 60 = 20g
    3. Name the method of separation (1mk)
      fractional crystalisation
  22. The table below gives elements represented by letters T,U,V,W,X,Y and their atomic numbers . (Letters are not the actual symbols.

    Element

    T

    U

    V

    W

    X

    V

    Atomic number

    12

    13

    14

    15

    16

    17

    1.                           
      1. How does the atomic radius of V compare with that of X? Explain. (2mks)
        v is larger than x
        v has a lower nuclear charge than x due to less number of prorons/ due to less effective nuclear charge
      2. Give the formula of the compound that could be formed between U and X. (1mk)
        U2X3
    2.                          
      1. Arrange the species T,T- and T+ in increasing order of size. (1mk)
        T+, T, T-
      2. Which of the ions X2+ and X2- is the most stable ? Explain. (2mks)
        X2-, gains electrons to attain an actet state
  23.                                
    1. What would be observed in sulphur IV Oxide is bubbled through acidified potassium. chromate VI (1mk)
      the orange acidified potassium chromate (VI) turns to green
    2. In an experiment, sulphur (IV) Oxide was dissolved in water to form solution M.
      1. State the observation made if a few drops of barium chloride solution immediately added to solution M (1mk)
        white ppt is formed
      2. Identify the spectator ions from the reaction b(i) above (1mk)
        H+ and Cl-
  24. Copper-64 has a half life of 12.8days.
    1. What is meant by the term half life (1mk)
      time taken for a given mass of nuclide to decay to half of its original mass
    2. What mass of a copper-64 will be left after 51.2 days starting with 20 g of the isotopes (2mks)
      51.2 = 4
      12.8
      (1/2)4 × 20 = 1.25g
    3. Give one use of radioactive isotopes in medicine (1mk)
      destroy cancerous cee/ sterilization of surgical instruments/ monitor growth of bones (any other)
  25.                              
    1. Zeolites (Na2X) is a complex compound used to soften hard water in the ion-exchange methods according to the equation below.
      Ca 2+ (aq) +Na2X (aq) → CaX(s) + 2Na+ (aq)
      After sometimes the Zeolites get exhausted and ceases to soften water. Write a reaction to show how Zeolite is regenarated. (1mk)
      CaX(s) + 2NaCl(aq) → CaCl2 (aq) + Na2X(s)
  26. Name the particle responsible for electrical conductivity on;
    1. Molten magnesium metal (1mk)
    2. Molten magnesium chloride (1mk)
  27. Carbon is one of the elements that exhibit allotropy
    1. Define the term allotrophy (1mk)
    2. Name two allotropes of carbon (1mk)
    3. Which allotrope of carbon is a good conductor of electricity. Explain. (2mks)

Download Chemistry P1 Questions and Answers - Momaliche 4 cycle Post Mock Exams 2021/2022.


Tap Here to Download for 50/-




Why download?

  • ✔ To read offline at any time.
  • ✔ To Print at your convenience
  • ✔ Share Easily with Friends / Students


Join our whatsapp group for latest updates
.
Subscribe now

access all the content at an affordable rate
or
Buy any individual paper or notes as a pdf via MPESA
and get it sent to you via WhatsApp

 

What does our community say about us?

Join our community on:

  • easyelimu app
  • Telegram
  • facebook page
  • twitter page
  • Pinterest