Chemistry Paper 1 Questions and Answers - Kassu Jet Pre Mocks 2022

Share via Whatsapp

Instructions to Candidates

  1. Write your Name, Adm Number and index number in the spaces provided above.
  2. Sign and write the date of examination in the spaces provided above
  3.  Answer ALL the questions in the spaces provided in the question paper
  4. KNEC Mathematical tables and/or electronic calculators may be used for calculations
  5. All working MUST be clearly shown where necessary
  6. Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing
  7. Candidates should answer the questions in English


QUESTIONS

  1. Give one danger of abusing bhang (1mark)
  2. Give one reason why a conical flask is preferred during a titration experiment over a beaker (1mark)
  3. The atomic number of iron is 26 and its mass number is 56. How many of each of the following particles is in Iron (III) ion?
    1. Protons………………………………………………. (½ mark)
    2. Neutrons………………………………………………. (1 mark)
    3. Electrons………………………………………………. (1mark)
  4. Study the diagram below and answer the questions that follow.
    4 dadada
    1. Between point B and point M which one should be heated first? Explain. (1mark)
    2. Write a chemical equation that occurs in the combustion tube (1mark)
    3. State and explain the observation made when gas X is passed over heated copper (II) oxide (2 marks)
  5. Lead carbonate was heated strongly in a boiling tube. Write the equation for the reaction that occurred. (1 mark)
  6. A mixture consists of three solids: lead (II) carbonate, iron filings, and sodium carbonate.
    Describe how to obtain pure lead (II) carbonate from the mixture. (3 marks)
  7. Chlorine gas is prepared in the laboratory by reacting a mixture of Potassium manganate (VII) and substance H. when dry chlorine is passed over heated aluminium foil, a white solid S is formed.
    1. Identify substances H and S (1 mark)
      H…………………………………………
      S…………………………………………
    2. Name the drying agent used to dry chlorine gas (1mark)
    3. State the observation that will be made when chlorine is bubbled through a solution of Iron (II) chloride (1mark)
  8. Diamond and graphite are two allotropes of carbon. Explain how graphite is suitable for the
    use as a lubricant. (1 mark)
  9. The following is a section of a radioactive decay series. Study it and answer the questions that follows
    9 aadadada
    1. Identify one characteristic of particle X (1mark)
    2. Write the nuclear equation for process I (1mark)
  10. You are provided with 200 cm3 of 0.5M lead (II) nitrate solution and 200 cm3 of 0.5M sodium chloride solution. Briefly describe how a dry sample of sodium nitrate crystals can be prepared (3 marks)
  11.  In an experiment, 120 cm3 of oxygen diffused through a porous pot in 20 seconds and 200 cm3 of gas Y diffused through the same porous pot in 60 seconds. If the density of oxygen is 1.4291 g/cm3, calculate the density gas Y. (2 marks)
  12.  A given mass of gas was placed in cylinder A as shown below and its volume and pressure measured at constant temperature as VA and PA respectively. The same mass was then placed into cylinder B and the piston pushed down as shown. The volume and the pressure exerted on the piston was also measured as VB and PB respectively. 
    12 adada
    1. State the mathematical expression that gives the correct relationship between the pressure and volume of the gas in both cylinders A and B at constant temperature. (1mark)
    2. Give one application of gas laws. (1mark)
  13. When a certain hydrocarbon is burnt completely in excess oxygen, 3.08 g of carbon (IV) oxide and 0.72 g of water were formed. If the molecular mass of the hydrocarbon is 184, determine the molecular formula of the hydrocarbon. (C=12, H=1) (3 marks)
  14. If 25.0cm3 of 0.1M H2SO4 solution neutralised a solution containing 1.06g of anhydrous sodium carbonate in 250cm3 of solution, calculate
    1. The molarity of sodium carbonate (Na=23, O=16, C=12) (1 ½ marks)
    2. Volume of sodium carbonate solution used (1 ½ marks)
  15. The solubility of salt W is 80g/100g of water at a temperature of 90ºC. A solution containing 84g of the salt was cooled to 50ºC.
    1. Define solubility (1mark)
    2. Calculate the total mass of crystals present if the solubility of salt W at 50ºC is 25g/100g of water (1 mark)
    3. Calculate the molarity of the solution at 500C (1 mark)
      (R.F.M of W=174.5)
  16. Given the equation for the reaction below
    NH3 (g) + H2O (l) ⇌ NH4 + (aq) +OH- (aq)
    1. State the Bronsted-Lowry definition of a base (1 mark)
    2. Identify the base in the backward reaction (1 mark)
  17. Magnesium and aluminium are both metals. In terms of structure and bonding, how does the melting point of their respective chlorides compare? (3 marks)
  18. The setup below shows laboratory preparation of nitrogen gas.
    18 adadada
    1. Write the equation for the reaction in which nitrogen gas is produced (1 mark)
    2. What property makes nitrogen gas to be collected as shown above (1 mark)
    3. Nitrogen gas is used in storage of semen under artificial insemination. Explain. (1 mark)
  19. The structure below represents two cleansing agents Q and P.
    Q- RCOO-Na+
    P- ROSO3-Na+
    1. Give one advantage and one disadvantage of using agent Q (2marks)
      Advantage
      Disadvantage
  20. The flow chart below shows some of the chemical properties of organic compounds starting with ethanol. Use it to answer the questions that follow.
    20 ssfsfsfsf
    1. Name the type of reaction in; (1 mark)
      1. Step II
      2.                          
        1. Step IV
        2.  Write the equation for the reaction in step I (1 mark)
        3. Give the structural formula and IUPAC name of compound B (1 mark)
          Structural formula
          IUPAC name (½ mark)
        4. State the major industrial application of the reaction in step III (1 mark)
  21. The general formula for a homologous series of a group organic compounds is CnH2n+1OH.
    1. Give the name of the structural formula of the fourth member of the series
      1. Name (1 mark)
      2. Structural formula (1 mark)
    2. Write the equation for the reaction between the molecule in (I) above and Propanoic acid (1 mark)
  22.                      
    1. The table below lists data relevant to the formation of MgCl2 solution.
      22 adadada
      Using the information provided, calculate the molar heat of hydration of chloride ions, ΔHhydration (Cl- (g)) (3 marks)
    2. Given that enthalpy of hydration of Ca2+ (g) is -1562 kJ/mol, suggest a reason why the enthalpy change of hydration of Mg2+(g) as shown in the table above is higher than the enthalpy change of hydration of Ca2+ (g) (1 mark)
  23. Petrol is a mixture of hydrocarbons. One of the hydrocarbons in petrol is octane, C8H18.
    1. Name the two products formed when octane is burnt in excess air. (1 mark)
    2. More petrol can be made by cracking less useful petroleum fractions
      1. Define the term cracking. (1 mark)
      2. Write the equation for the cracking of dodecane, C12H26 to form ethene and one other hydrocarbon (1 mark)
      3. Give the name of the hydrocarbons homologous series to which ethene belongs (1 mark)
  24.  A powder is suspected to be containing sulphite ions. Given, 2M nitric acid, dilute barium nitrate solution, Acidified potassium manganate (VII) reagents and other necessary laboratory apparatus, describe how one can confirm the presence of the ions. (3 marks)
  25. Ethanoic acid reacts with ethanol to form a product that has a pleasant smell called an ester and water. When the reaction is at an equilibrium, a few drops of concentrated sulphuric acid were added, followed by warming.
    1. What is the effect of adding concentrated sulphuric acid on;
      1.  The position of the equilibrium of the mixture? (1 mark)
      2. The yield of the ester (1 mark)
    2. The forward reaction in the equilibrium is referred to as esterification. What is the name of the reverse reaction? (1 mark)
    3. Explain the effect of rise in temperature on the yield of products of a reaction with a molar enthalpy change of -92kJ/mol. (2 marks)
  26. A wet wooden splint was dipped in manganese (IV) oxide powder and then soaked in hydrogen peroxide solution as shown below.
    26 adadad
    1. State and explain the observation that was made (2 marks)
    2. Write the equation for the reaction that occurred (1 mark)
  27. The setup below shows the process of electrolysis of molten lead (II) fluoride. Use it to answer the questions that follow.
    27 addadad
    1. Identify the electrodes labelled A and B (1 mark)
      A……………………………
      B……………………………
    2. Indicate the direction of flow of electrons on the diagram (1 mark)
    3. State and explain the observation made on electrode B (2 marks)
    4. Give any one application of electrolysis (1 mark)
  28. The graphs J, K and L below shows the general trend in the properties of period 3 elements
    (Na to Cl). Use them to answer the questions that follow.
    28 sfsfsfs
    Select a graph that represents the variation in;
    a. Ionic radius. (½ mark)
    b. Atomic radius. Explain. (1½ marks)
  29. Aluminium objects do not need protection from corrosion while Iron objects must be protected from corrosion. Explain. (2 marks)


MARKING SCHEME

  1. Give one danger of abusing bhang (1mark)
    • hallucination
    • brain damage
    • addiction
  2. Give one reason why a conical flask is preferred during a titration experiment over a beaker (1mark)
    • has a long neck that prevents splashing of the liquid
  3. The atomic number of iron is 26 and its mass number is 56. How many of each of the following particles is in Iron (III) ion?
    1. Protons………26……. (½ mark)
    2. Neutrons………30……(56 - 26). (1 mark)
    3. Electrons……26 - 3  = 26………. (1mark)
  4. Study the diagram below and answer the questions that follow.
    4 dadada
    1. Between point B and point M which one should be heated first? Explain. (1mark)
      • B - to produce steam that drives out air from combustion tube that reacts with iron
    2. Write a chemical equation that occurs in the combustion tube (1mark)
      • 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
    3. State and explain the observation made when gas X is passed over heated copper (II) oxide (2 marks)
      • The black solids changes to brown
      • CuO is reduced to copper metal
  5. Lead carbonate was heated strongly in a boiling tube. Write the equation for the reaction that occurred. (1 mark)
    • PbCO3(s) (heat) → PbO(s) + CO2(g)
  6. A mixture consists of three solids: lead (II) carbonate, iron filings, and sodium carbonate.
    Describe how to obtain pure lead (II) carbonate from the mixture. (3 marks)
    • spread the mixture on a paperon a flat surface
    • carefully pass a magnet over it to remove iron
    • place the remaining mixture in a glaass beaker
    • add water and stir: Na2CO3 dissolves
    • filter the mixture
    • wash the residue with distilled water
    • Dry the PbCO3 residue by placing between filter papers
  7. Chlorine gas is prepared in the laboratory by reacting a mixture of Potassium manganate (VII) and substance H. when dry chlorine is passed over heated aluminium foil, a white solid S is formed.
    1. Identify substances H and S (1 mark)
      H…concentrated hydrochloric acid or HCL
      S…Aluminium chloride
    2. Name the drying agent used to dry chlorine gas (1mark)
      • Concentrated sulphuric (VI) acid
    3. State the observation that will be made when chlorine is bubbled through a solution of Iron (II) chloride (1mark)
      • the solution changes from green to orange / yellow
  8. Diamond and graphite are two allotropes of carbon. Explain how graphite is suitable for the
    use as a lubricant. (1 mark)
    • graphite is made of hexagonal layers connected by weak van der waals forces that enables them to slide over each other
  9. The following is a section of a radioactive decay series. Study it and answer the questions that follows
    9 aadadada
    1. Identify one characteristic of particle X (1mark)
      • low penetrating power
      • positively charged
    2. Write the nuclear equation for process I (1mark)
      ii fsfsf
  10. You are provided with 200 cm3 of 0.5M lead (II) nitrate solution and 200 cm3 of 0.5M sodium chloride solution. Briefly describe how a dry sample of sodium nitrate crystals can be prepared (3 marks)
    • measure 100cm3 of 0.5m Pb(NO3)2 and place in a beaker
    • Add the 200cm3 of 0.5m NaCl and stir the mixture
    • filter the mixture and retain the filtrate of NaNo3
    • Heat the filtrate to saturation
    • Transfer to evaporating dish and allow to cool and form crystals
    • Pour off the mother liquor and dry the crystals by placing between filter papers
  11.  In an experiment, 120 cm3 of oxygen diffused through a porous pot in 20 seconds and 200 cm3 of gas Y diffused through the same porous pot in 60 seconds. If the density of oxygen is 1.4291 g/cm3, calculate the density gas Y. (2 marks)
    11 sdfsda
  12.  A given mass of gas was placed in cylinder A as shown below and its volume and pressure measured at constant temperature as VA and PA respectively. The same mass was then placed into cylinder B and the piston pushed down as shown. The volume and the pressure exerted on the piston was also measured as VB and PB respectively. 
    12 adada
    1. State the mathematical expression that gives the correct relationship between the pressure and volume of the gas in both cylinders A and B at constant temperature. (1mark)
      • PAVA = PBVB
    2. Give one application of gas laws. (1mark)
      • inflating weather ballons
      • inflating vehicle tires/aeroplans
  13. When a certain hydrocarbon is burnt completely in excess oxygen, 3.08 g of carbon (IV) oxide and 0.72 g of water were formed. If the molecular mass of the hydrocarbon is 184, determine the molecular formula of the hydrocarbon. (C=12, H=1) (3 marks)
    13 ahhgdhada
  14. If 25.0cm3 of 0.1M H2SO4 solution neutralised a solution containing 1.06g of anhydrous sodium carbonate in 250cm3 of solution, calculate
    1. The molarity of sodium carbonate (Na=23, O=16, C=12) (1 ½ marks)
      • molarity = mass/RFM
        Na2CO3 = (2 x 23) + 12(16 x 3) = 106
        molarity = 1.06 x 4
                           106
        = 0.04m
        or
        moles in 250cm3  = 1.06 = 0.01
                                         106
        molarity = 1000 x 0.01
                          250
        = 0.04 m
    2. Volume of sodium carbonate solution used (1 ½ marks)
      • moles of H2SO4 = 25/1000 x 0.1
        H2SO4 + Na2CO3 → Na2SO4 + CO2 + H2O
        1 mol                 1 mol
        moles of NaCO3 = 0.0025 mol
        1000 cm3 → 0.04 mol
        ?  →   0.0025 mol
        0.0025 x 1000
            0.04
        = 62.5 cm3
  15. The solubility of salt W is 80g/100g of water at a temperature of 90ºC. A solution containing 84g of the salt was cooled to 50ºC.
    1. Define solubility (1mark)
      • the amount of solute that ssaturates 100g of water at a given temperature
    2. Calculate the total mass of crystals present if the solubility of salt W at 50ºC is 25g/100g of water (1 mark)
      • 84 - 25
        = 59
    3. Calculate the molarity of the solution at 50ºC (1 mark)
      (R.F.M of W=174.5)
      • moles of w in 100cm3 = 25/174.5 = 0.14327
        molarity = 0.14327 x 1000 = 1.4327m
                           100
  16. Given the equation for the reaction below
    NH3 (g) + H2O (l) ⇌ NH4 + (aq) +OH- (aq)
    1. State the Bronsted-Lowry definition of a base (1 mark)
      • proton acceptor
    2. Identify the base in the backward reaction (1 mark)
      • OH-
  17. Magnesium and aluminium are both metals. In terms of structure and bonding, how does the melting point of their respective chlorides compare? (3 marks)
    • chloride of Mg has higher melting point than chloride of Al. MgCl2 has strong ionic bonds in a giant ionic structure
      AlCl3 is molecular melting covalent bonds. It therefore has weak van der walls forces between molecules.
  18. The setup below shows laboratory preparation of nitrogen gas.
    18 adadada
    1. Write the equation for the reaction in which nitrogen gas is produced (1 mark)
      • NH4NO2(s) → 2H2O(g) + N2(g)
    2. What property makes nitrogen gas to be collected as shown above (1 mark)
      • slightly soluble in water
      • does not react with water
    3. Nitrogen gas is used in storage of semen under artificial insemination. Explain. (1 mark)
      • it has a low freezing point
  19. The structure below represents two cleansing agents Q and P.
    Q- RCOO-Na+
    P- ROSO3-Na+
    1. Give one advantage and one disadvantage of using agent Q (2marks)
      Advantage
      forms scum with hard water
      Disadvantage
      less expensive - does not pollute the environment
  20. The flow chart below shows some of the chemical properties of organic compounds starting with ethanol. Use it to answer the questions that follow.
    20 ssfsfsfsf
    1. Name the type of reaction in; (1 mark)
      1. Step II - dehydration
      2.                          
        1. Step IV - addiction
        2.  Write the equation for the reaction in step I (1 mark)
          • 2CH3CH2OH + 2Na → 2CH3CH2ONa + H2
        3. Give the structural formula and IUPAC name of compound B (1 mark)
          Structural formula
          iii sfsfsfs
          IUPAC name (½ mark)
          chloroethane
        4. State the major industrial application of the reaction in step III (1 mark)
          • manufacture of margarine/converson of oils into fats
  21. The general formula for a homologous series of a group organic compounds is CnH2n+1OH.
    1. Give the name of the structural formula of the fourth member of the series
      1. Name (1 mark)
        • Butanol
      2. Structural formula (1 mark)
        ii 2 adadad
    2. Write the equation for the reaction between the molecule in (I) above and Propanoic acid (1 mark)
      ii 2 adadad
  22.                      
    1. The table below lists data relevant to the formation of MgCl2 solution.
      22 adadada
      Using the information provided, calculate the molar heat of hydration of chloride ions, ΔHhydration (Cl- (g)) (3 marks)
      math uygduyada
    2. Given that enthalpy of hydration of Ca2+ (g) is -1562 kJ/mol, suggest a reason why the enthalpy change of hydration of Mg2+(g) as shown in the table above is higher than the enthalpy change of hydration of Ca2+ (g) (1 mark)
      Mg2+ is smalle than Ca2+ and therefore attracts water molecules more readily during hydration
  23. Petrol is a mixture of hydrocarbons. One of the hydrocarbons in petrol is octane, C8H18.
    1. Name the two products formed when octane is burnt in excess air. (1 mark)
      • water
      • carbon(IV) oxide
    2. More petrol can be made by cracking less useful petroleum fractions
      1. Define the term cracking. (1 mark)
        • breaking of long chain hydrocarbons into more useful short chain hydrocarbons
      2. Write the equation for the cracking of dodecane, C12H26 to form ethene and one other hydrocarbon (1 mark)
        • C12H2→ C2H4 + C10H22
      3. Give the name of the hydrocarbons homologous series to which ethene belongs (1 mark)
        • Alkene
  24.  A powder is suspected to be containing sulphite ions. Given, 2M nitric acid, dilute barium nitrate solution, Acidified potassium manganate (VII) reagents and other necessary laboratory apparatus, describe how one can confirm the presence of the ions. (3 marks)
    • place the solid in a boiling tube and add water then dhake to dissolve. Divide into two portions of 2 cm3.
    • To first portion add dilute Ba(NO3)2 followed by HNO3.
    • It forms white precipitate that dissolves in acid
    • To second portion, add drops of H+/KMnO4. The colour changes from purple to colourless
  25. Ethanoic acid reacts with ethanol to form a product that has a pleasant smell called an ester and water. When the reaction is at an equilibrium, a few drops of concentrated sulphuric acid were added, followed by warming.
    1. What is the effect of adding concentrated sulphuric acid on;
      1.  The position of the equilibrium of the mixture? (1 mark)
        • No effect . As a catalyst there is no effect on equilibrium position
      2. The yield of the ester (1 mark)
        • No effect. Catalyst doesn't affect amount of products
    2. The forward reaction in the equilibrium is referred to as esterification. What is the name of the reverse reaction? (1 mark)
      • acidic hydrolysis
    3. Explain the effect of rise in temperature on the yield of products of a reaction with a molar enthalpy change of -92kJ/mol. (2 marks)
      • the yield lowers/reduces
      • increase in temperature does not favour exothermic reactions
  26. A wet wooden splint was dipped in manganese (IV) oxide powder and then soaked in hydrogen peroxide solution as shown below.
    26 adadad
    1. State and explain the observation that was made (2 marks)
      • effervescence // bubbles
        there is production of oxygen gas
    2. Write the equation for the reaction that occurred (1 mark)
                               MnO2
      2H2O2(l)         →                  2H2O(l) + O2(l)
  27. The setup below shows the process of electrolysis of molten lead (II) fluoride. Use it to answer the questions that follow.
    27 auygdad
    1. Identify the electrodes labelled A and B (1 mark)
      A…cathode……
      B…anode…………
    2. Indicate the direction of flow of electrons on the diagram (1 mark)
      • (on diagram)
    3. State and explain the observation made on electrode B (2 marks)
      • pale yellow gas is evolved
        floride ions lose electrons to form F2 gas
        Accept: 2F(aq) → F2(g) + 2e-
    4. Give any one application of electrolysis (1 mark)
      • etraction of metals 
      • manufacture of pure chemicals
  28. The graphs J, K and L below shows the general trend in the properties of period 3 elements
    (Na to Cl). Use them to answer the questions that follow.
    28 sfsfsfs
    Select a graph that represents the variation in;
    a. Ionic radius. (½ mark)
    L
    b. Atomic radius. Explain. (1½ marks)
    J
    there is a reduction in atomic size/radius to due increasing effective nuclear force as the protons increase
  29. Aluminium objects do not need protection from corrosion while Iron objects must be protected from corrosion. Explain. (2 marks)
    • aluminium once coated by a thin oxide layer there is no need for protection since the layer is inert preventing further corrosion
    • iron needs protection since the porous oxide (rust) layer allows continued corrosion

Download Chemistry Paper 1 Questions and Answers - Kassu Jet Pre Mocks 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