Chemistry Paper 1 Questions and Answers - MECS Cluster Joint Pre Mock Exams 2021/2022

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CHEMISTRY 233/1
PAPER 1 

  1. Air passed through several reagents as shown below
    MECChemp1q1
    1. What is the role of conc potassium hydroxide? (1mk)
    2. Write an equation that takes place in step III with Magnesium powder. (1mk)
    3. Name one gas that was collected from the process. (1mk)
  2. Name two examples of physical changes. (2mks)
  3. A gas at 27ºC and 750mmHg pressure was found to occupy 360cm3. Calculate the temperature at which the same mass of gas will occupy twice the volume at a pressure of 1000mmHg. (2mks)
  4.        
    1. In the equation below, identify the reagent that acts as a base. (1mk)
      H2O2(aq) + H2O(l)   ⇌ H3O+(aq) + HO2-(aq)
    2. Give a reason for your answer in (a) above (1mk)
  5.           
    1. When left in the open air, anhydrous calcium chloride increases in mass. Explain (1mk)
    2. What name is given to the process in a above? (1mk)
  6. Study the chart below and answer the questions that follow.
    MECChemp1q6
    1. Identify
      1. Gas A (1mk)
      2. White precipitate. (1mk)
    2. Write an ionic equation for the formation of white precipitate. (1mk)
  7. A student was supplied with a colourless liquid suspected to be water. Describe a chemical test that would be carried out to show that the liquid was water. (1mk)
  8. In an experiment to determine solubility of sodium chloride, 13.2g of saturated sodium chloride solution at 18ºC was evaporated to dryness. 3.6g of the salt was left after complete evaporation of water.Determine the solubility of sodium chloride at 18ºC. (3mks)
  9.               
    1. State Graham’s law of diffusion. (1mk)
    2. A volume of 120cm3 of nitrogen gas diffused through a membrane in 40 seconds, how long will 240cm3 of carbon (IV) Oxide take to diffuse through the membrane under the same conditions. (2mks)
  10. A student was carrying out an experiment using Barium sulphate. The salt accidentally got mixed up with sodium sulphate. Describe how the student would get a dry sample of Barium sulphate. (3mks)
  11. The diagram below represents the Frasch process. Study it and answer the questions that follow
    MECChemp1q11
    1. Name;
      A½mk)
      B ( ½mk)
      C ( ½mk)
    2. Why is C pumped to the sulphurdeposit. ( ½ mk)
    3. Which property of sulphur enables it to be extracted by the method above.(1mk)
  12. An element A has two isotopes 50A and 52A. The relative atomic mass of A is 51.5
    1. Determine the percentage abundance of each isotope. (2mks)
    2. Define the term isotopy (1mk)
  13. Study the table below and answer the questions that follow. The letters are not the actual chemical symbols of the elements.
    Element Atomic number Atomic mass
     W  20  40
     X  9  19
     Y  10  20
     Z  17  35.5

    1. Identify elements that belong to the same group and give a reason. (2mks)
    2. Which element is a metal. (1mk)
  14. Study the information given in the table below and answer the questions that follow
    Bond C - H Cl - Cl C - Cl H - Cl
    Average bond enthalpy (KJmol-1) Breaking of bond)  414  244  326  431
    1. Calculate the enthalpy change for the reaction (3mks)
      CH4(g) + Cl2(g) uv light  > CH3Cl(g) + HCl(g)
    2. Is the reaction exothermic or endothermic?
      Explain your answer. (1mk)
  15. Study the flow chart below and answer the questions that follow
    1. Write the chemical formulae of the following;
      1. Green solid A (1mk)
      2. White precipitate E (1mk)
    2. Write a chemical equation for the reaction taking place in the following steps.
      1. Step 1 ( ½ mk)
      2. Step 3 ( ½ mk)
  16. Soap solution was added to the three samples of water and the amount of soap required to form lather with 1 litre of each sample of water before and after boiling was recorded as shown below.
       I  II III
    Volume of soap before water is boiled 30  5 12
     Vole of soap after boiling  30  5 5

    1. Explain the change in the volume of soap solution used in experiment III. (1mk)
    2. Why was the volume of soap used in experiment II so low. (1mk)
  17.       
    1. State Avogadro’s law (1mk)
    2. 100cm3 of hydrogen was mixed with 300cm3 of chlorine and the mixture allowed to react. Determine the maximum volume of hydrogen chloride gas that would form. (2mks)
  18. The table below shows the tests that were carried out on solid R and the observations made
    Test Observations

    i)Solid R was heated.

    ii)Dilute hydrochloric acid was added to solid R.

    iii)To the colourless solution obtained in test II excess sodium hydroxide solution was added.

    Solid R turned from white to yellow.

    Colourless solution was formed.

    A white precipitate was formed which dissolved to form a colourless solution.

    Write the formula of cation in;
    1. Solid N (1mk)
    2. Colourless solution formed in test III (1mk)
  19. The diagram below is a set up of apparatus used during electrolysis of molten copper(II) iodide
    MECChemp1q19
    1. List all ions present in the electrolyte. (2mks)
    2. Write half equations for reactions in electrodes;
      1. X (1mk)
      2. Y
  20. 2.4 g of magnesium were reacted with excess dilute hydrochloric acid at room temperature and pressure. Calculate the volume of hydrogen that was formed (Molar gas volume at R.T.P = 24dm3 Mg = 24) (3mks)
  21. Write the chemical formula of sodium sulphate. (1mk)
  22. Sulphuric (VI) acid is manufactured using the contact process.
    1. State the catalyst used in the process. (1mk)
    2. State the optimum conditions for the process. (1mk)
    3. Explain how environmental pollution by the process is minimized. (1mk)
  23. A student had 2 g of sodium hydroxide and z grammes of sulphuric (VI) acid. Which of the compound contain more of hydrogen atoms. (3mks)
    (H =1, S = 32, O = 16, Na =23)
  24. State and explain the observations made when concentrated sulphuric (VI) acid is added to glucose. (2mks)
  25. Name an ion which must be present in acidic solution. (1mk)
  26. Dry blue litmus paper was put into a gas jar of dry hydrogen chloride gas. State and explain the observations made. (2mks)
  27. 250cm3 of water was added to 300cm3 of 2M sulphuric vi acid. determine the new concentration of the solution (2mks)
  28. Liquid P and Q mix forming a solution and have different boiling points.
    1. Name a suitable method of separation that would be used to separate the two liquids. (1mk)
    2. What property makes it possible to separate the two liquids P and Q. (1mk)
  29. Describe a chemical test for chlorine. (2mks)
  30. Describe how zinc sulphate crystals can be prepared. (2mks)
  31. Use the information in the table to answer questions that follow. (The letters are not the actual chemical symbols of the element)
    Element Atomic radius ionic radius
     M  0.158  0.097
     N  0.202  0.132
     L  0.133  0.061

    1. Do these elements belong to a metallic or a non – metallic group? Give a reason. (2mks)
    2. Which element is the most reactive? Explain. (1mk)
  32. Study the diagram below and answer the questions that follow
    MECChemp1q32
    1. Name the flame above (1mk)
    2. Name parts A,B,C and D of the flame (2mks)

MARKING SCHEME

  1. Air passed through several reagents as shown below
    1. What is the role of conc potassium hydroxide? (1mk)
      • To remove CO2 from air by reacting with it

    2. Write an equation that takes place in step III with Magnesium powder.(1mk)
      • 3Mg(s) +N2(g) → Mg3N2(s)

    3. Name one gas that was collected from the process. (1mk)
      • Argon
      • Neon
      • Helium
      • xenon

  2. Name two examples of physical changes. (2mks)
    • Melting
    • Sublimatation
    • Vapourization
    • Heat ZnO
    • Heating PbO

  3. A gas at 270C and 750mmHg pressure was found to occupy 360cm3. Calculate the temperature at which the same mass of gas will occupy twice the volume at a pressure of 1000mmHg. (2mks)
    • T1 = 300k
      P1 = 750mmHg
      V1 = 360cm3
      T2 =
      V2 = 720cm3
      P2 = 1000mmHg
      P₁V₁= P₂V₂
       T ₁       T₂
      750 X 360 = 1000 X 720
            300             T₂
      T2 =  1000 x 720 x 300
                     750 x 360
      = 800k
      =527ºC
  4.        
    1. In the equation below, identify the reagent that acts as a base. (1mk)
      • H2O2(aq) + H2O(l)   ⇌ H3O+(aq) + HO2-(aq)
        H2O it accepts a proton from H2O2
    2. Give a reason for your answer in (a) above (1mk)
      • from it accepts a protonH2O2
  5.         
    1. When left in the open air, anhydrous calcium chloride increases in mass.Explain(1mk)
      • it absorbed water from the atmosphere to form a solution

    2. What name is given to the process ina above? (1mk)
      • deliquescence

  6. Study the chart below and answer the questions that follow.
    1. Identify
      1. Gas A   
        • HCl or hydrogen chloride gas (1mk)

      2. White precipitate.
        • Silver chloride / Ag2CO3 (1mk)

    2. Write an ionic equation for the formation of white precipitate. (1mk)
      • 2Ag+(aq) + CO32-(aq)  → Ag2 CO3(s)

  7. A student was supplied with a colourless liquid suspected to be water. Describe a chemical test that would be carried out to show that the liquid was water.(1mk)
    • Add the liquid to anhydrous CUSO4 if it turns from white to blue the liquid is water
      NB anhydrous C0Cl2 can also be use

  8. In an experiment to determine solubility of sodium chloride, 13.2g of saturated sodium chloride solution at 18ºC was evaporated to dryness. 3.6g of the salt was left after complete evaporation of water.Determine the solubility of sodium chloride at 18ºC.(3mks)
    • 13.2 - 3.6 = 9.6
      9.6g – 3.6
      100 -  3.6 x 100 /9.6 = 37.5g/100g of H2O penalize ½ if unit not given

  9.          
    1. State Graham’s law of diffusion. (1mk)
      • the rate of diffusion of a gas is inversely proportional to the square root of its density at constant temp and pressure.

    2. A volume of 120cm3 of nitrogen gas diffused through a membrane in 40 seconds, how long will 240cm3 of carbon (IV) Oxide take to diffuse through the membrane under the same conditions. (3mks)
            TN₂        =     TCO₂        
      √RMMN2        √RMMCO2

      TCO₂ = 80 x √44
                       √28
        80   =  TCO₂ 
      √28       √44
      MECChemp1q9c
      3√28 = 240/T√44

      240 x √44
         3 x √28
      TCO₂ =100.29sec

  10. A student was carrying out an experiment using Barium sulphate. The salt accidentally got mixed up with sodium sulphate. Describe how the student would get a dry sample of Barium sulphate. (3mks)
    • Add water to the mixture and stir
    • Filter the resulting mixture BaSO4 is collected as residue while Na2SO4 solution is collected as filtrate
    • Rinse the residue with distilled water
    • Dry the residue between filter paper

  11. The diagram below represents the Frasch process. Study it and answer the questions that follow
    1. Name;
      1.  Hot compressed air ( ½mk)
      2. Molten sulphur/water mixture ( ½mk)
      3. supper heated water at 170ºC ( ½mk)
    2. Why is C pumped to the sulphurdeposit. ( ½ mk)
      • To melt sulphur

    3. Which property of sulphur enables it to be extracted by the method above.(1mk)
      • It has a low melting point

  12. An element A has two isotopes 50A and 52A. The relative atomic mass of A is 51.5
    1. Determine the percentage abundance of each isotope. (2mks)
      • -2x = -50
        x = 25
        50A – 25%
        52A – 75%

    2. Define the term isotopy (1mk)
      • Existence of atoms with the same atomic number but with different mass numbers

  13. Study the table below and answer the questions that follow. The letters are not the actual chemical symbols of the elements.
    Element Atomic number Atomic mass
     W  20  40
     X  9  19
     Y  10  20
     Z  17  35.5

    1. Identify elements that belong to the same group and give a reason.(2mks)
      • X and Z because they both have 7 electrons in the outermost occupied energy level

    2. Which element is a metal. (1mk)
      • W

  14. Study the information given in the table below and answer the questions that follow
    1. Calculate the enthalpy change for the reaction (3mks)
      • Bond broken energy required ∆H = -(759 – 658)
        C – H 414 = - 99kj
        Cl – Cl 244
        658
        Bond formed energy lost
        C- cl 326
        H – cl 431
        757

    2. Is the reaction exothermic or endothermic? Explain your answer. (1mk)
      • Exothermic energy given out during bond formation is greater than energy gained during bond breaking

  15. Study the flow chart below and answer the questions that follow
    1. Write the chemical formulae of the following;
      1. Green solution E (1mk)
        • Fe(NO3)2

      2. White precipitate E (1mk)
        • CaCO3

    2. Write a chemical equation for the reaction taking place in the following steps.
      1. Step 1
        • FeCO3(s) → FeO(s) + CO2(g) ( ½ mk)

      2. Step 3
        • FeO(s) + 2HNO3(aq) Fe(NO3)2(aq) + H2O(l) ( ½ mk)

  16. Soap solution was added to the three samples of water and the amount of soap required to form lather with 1 litre of each sample of water before and after boiling was recorded as shown below.
    1. Explain the change in the volume of soap solution used in experiment III.(1mk)
      • The sample of water was temporary hard and therefore when boiled the hardness was removed.

    2. Why was the volume of soap used in experiment II so low. (1mk)
      • The sample of water was softwater
  17.              
    1. State Avogadro’s law (1mk)
      • at constant temperature and pressure equal volumes of gas contain equal number of molecules

    2. 100cm3 of hydrogen was mixed with 300cm3 of chlorine and the mixture allowed to react. Determine the maximum volume of hydrogen chloride gas that would form.(2mks)
      • H2 + Cl2(g) → 2HCl(g)
        100  100        200cm3

  18. The table below shows the tests that were carried out on solid R and the observations made
    Write the formula of cation in;
    1. Solid N (1mk)
      • Zn2+

    2. Colourless solution formed in test III (1mk)
      • Na+

  19. The diagram below is a set up of apparatus used during electrolysis of molten copper(II) iodide
    1. List all ions present in the electrolyte. (2mks)
      • CU2+ and I- ions

    2. Write half equations for reactions in electrodes;
      1. X
        • 2J-  → I2(g) + 2e- (1mk)

      2. Y
        • CU2+(l) + 2e-  → Cu(s)

  20. 2.4 g of magnesium were reacted with excess dilute hydrochloric acid at room temperature and pressure. Calculate the volume of hydrogen that was formed (Molar gas volume at R.T.P = 24dm3 Mg = 24) (3mks)
    • 2.4 = 0.1moles
      24
      2HCl(aq) + Mg(s) → MgCl(2)(aq) + H2(g)
      0.2moles 0.1moles 0.1moles0.1moles
      1 mole of H2 – 24dm3
      0.1moles – 2.4 x 0.1 = 2.4dm3
      1

  21. Write the chemical formula of sodium sulphate. (1mk)
    • Na2SO4

  22. Sulphuric (VI) acid is manufactured using the contact process.
    1. State the catalyst used in the process. (1mk)
      • Vanadium(V) oxide/ V2O5// platinized asbestos

    2. State the optimum conditions for the process. (1mk)
      • 450ºC

    3. Explain how environmental pollution by the process is minimized. (1mk)
      • Scrubbing the exhaust fume by passing them through a chimney packed with calium hydroxide

  23. A student had 2 g of sodium hydroxide and 2grammes of sulphuric (VI) acid. Which of the compound contain more of hydrogen atoms. (3mks)
    (H =1, S = 32, O = 16, Na =23)
    • NaOH   H2SO4
      2              2
      40            98
      Mass of substance 0.05 moles 0.02041
      Moles of hydrogen atoms 0.05 moles 0.04082 moles
      2g of NaOH

  24. State and explain the observations made when concentrated sulphuric (VI) acid is added to glucose.(2mks)
    • The solid changed from white to black .con. H2SO4 acid dehydrate glucose to carbon.

  25. Name an ion which must be present in acidic solution. (1mk)
    • Hydrogen ion

  26. Dry blue litmus paper was put into a gas jar of dry hydrogen chloride gas. State and explain the observations made. (2mks)
    • The blue litmus retain its colour. Hcl does not have acidic when dry

  27.                    
    • M1V1=M2V2
      2 X 300 = 1.091M
      550

  28. Liquid P and Q mix forming a solution and have different boiling points.
    1. Name a suitable method of separation that would be used to separate the two liquids. (1mk)
      • Fractional distillation/simple distillation

    2. What property makes it possible to separate the two liquids P and Q.(1mk)
      • They have different boiling points

  29. Describe a chemical test for chlorine. (2mks)
    • Introduce a moist blue litmus paper to the gas
    • The paper turned red and the white

  30. Describe how zinc sulphate crystals can be prepared. (2mks)
    • Add excess zinc to dil.sulphuric (VI) acid
    • Filter the mixture ZnSO4(aq) is collected as filtrate
    • Heat the solution to evaporate water until the solution is saturated
    • Leave the solution to cool for crystals to grow
    • Filter the crystals and dry them between filter papers

  31. Use the information in the table to answer questions that follow. (The letters are not the actual chemical symbols of the element)
    1. Do these elements belong to a metallic or a non – metallic group? Give a reason.(2mks)
      • Metals ionic radius is shorter than the atomic radius

    2. Which element is the most reactive? Explain. (1mk)
      • N. it has the longest atomic radius and therefore has lest ionization energy

  32. Study the diagram below and answer the questions that follow
    1. Name the flame above (1mk)
      • luminous

    2. Name parts A,B,C and D of the flame (2mks)
      • A - Thin outer region
      • B - Bright – yellow region
      • C – Almost colourles
      • D – Blue region

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