Chemistry Questions and Answers - Form 4 Mid Term 1 Exams 2023

Share via Whatsapp
  1. A student set up the following apparatus in order to determine percentage of Oxygen by volume of air.
           ChemF42023MT1Q1
    1. State and explain the observations made on the moist iron wool at the end of theexperiment (after a week). (1mk)
    2. Give the expression of the percentage of oxygen by volume in the air in terms of the letter X, W,YandZinthediagram. (1mk)
    3. Write the formula of substance T. (1mk)
  2. The paper chromatography below shows the identification of unknown metal ion E and F. Thereference ions are K,L,M and N are shown. The experiment was done in ascending method.
           ChemF42023MT1Q2
    1. Name the ions in the mixture E. (1mk)
    2. Mixture F contains all the three ions. On the diagram show the chromatogram of  F. (1mk)
    3. Comment on the ion N in the diagram. (1mk)
  3. The following data gives pH values of solutions A, B and C.
     Solution  A   B   C 
     PH  13.6   6.9   1.3 
    1. Which solution named produce carbon (IV) oxide where reacted with a carbonate? (1mk)
    2. Write an ionic equation to show how the above reaction a(i) would be represented (1mk)
    3. What would be the colour of solution A after adding a few drops of phenolphthalein? (1mk)
  4. Study the table below.
     Metal  Reaction with air   Reaction with water   Reaction with dilute acid 
     A  Reacts  Reacts slowly  Reacts
     B  Does not react  Does not react  Does not react
     C  Reacts  Reacts  Reacts vigorously
    1. Which metal is likely to be magnesium? (1mk)
    2. Which metal may be used as a cooking pot? (1mk)
    3. Arrange the metals in order of reacting starting with the most reactive. (1mk)
  5. An element Q has atomic number 3, relative atomic mass 6.94 and consists of two isotopes of mass 6.0 and 7.0.
    1. What is the mass number of the more abundant isotope of Q? Give a reason for your answer. (1mk)
    2. Calculate the percentage abundant of the isotope which is more abundant. (2mks)
  6. Below is a scheme of some reactions starting with but-2-ene. Study it and answer the questions that follows.
          ChemF42023MT1Q7
    1. Name Y, X and T.      (1 ½ mks)
    2. Give the name of the following organic compounds.                              ( 1 ½ mks)

      1. ChemF42023MT1Q7bi
      2.  
        ChemF42023MT1Q7bii
      3.  
        ChemF42023MT1Q7biii
  7. An element Y has the electronic configuration of 2.8.5.
    1. Write the formula of the most stable anion formed when element Y ionizes. (1mk)
    2. Write the formula of the compound formed by X and Y if the ion of x is represented as X2+ (1mk)
    3. Explain the difference between the atomic radius of element Y and its ionic radius. (1mk)
  8. Using dots(.) and crosses (x) diagram show he bonding in the following compounds.
    1. Lithium oxide ( Li= 3, O=8). (1mk)
    2. Carbon(II) oxide ( C =6, O=8) (1mk)
  9. Starting with zinc sulphate solution describe how a sample of zinc oxide can be obtained (3mks)
  10. The diagram below shows a set up that can be used for preparation of solid T in the laboratory.
              ChemF42023MT1Q10
    1. What condition must be included in the above apparatus for solid T to be formed? (1mk)
    2. Name the solid:
      1. Q…………………………………………………………………………………………. ( ½ mk)
      2. T………………………………………………………………………………………… ( ½ mk)
    3. Why is it possible to collect T as shown? (1mk)
  11. Below is a table showing elements in group II of the periodic table. Study it and answer the questions that below.
     Element  1st ionization energy (KJ/mol)   2nd ionization energy (KJ/mol) 
     Magnesium  900  1800 
     Beryllium  736  1450 
     Calcium  590   1150 
    1. What is ionization energy? (1mk)
    2. Explain why 2nd ionization energy of the elements is larger compared to 1st ionization. (2mks)
  12. Use the thermo chemical equations below to answer the questions that follow.
    C2H2 +  7/2O2(g)  →   2 CO2(g) + 3H2O(l)   ΔH = -1560KJ/MOL
    C(s) + O2(g)  →  CO2 (g)                              ΔH = -394KJ/MOL
    H2(g) + ½ O2(g)  →  H2O (g)                         ΔH= -286KJ/MOL
    Draw an energy cycle diagram to represent the information above and use it to calculate the heat of formation of ethyne (3mks)
  13. A student prepared ammonia gas and let it into a solution of zinc sulphate using the arrangement shown below.
            ChemF42023MT1Q13
    1. State and explain the observations that were made in a beaker.        (2mks)
    2. Write the ionic equation involving zinc ions.                                 (1mk)
  14. The melting point of phosphorus trichloride is 90°C while that of magnesium chloride in 715°C inmterms of structures and bonding explain the differences in their melting point. (3mks)
  15.  
    1. Name one property of Neon that makes it possible to be used in electric lamps. (1mk)
    2. Name any other use of Argon other than in electric lamps. (1mk)
  16. A compound with molecular C2H6O reacts with sodium metal forming a basic solution.
    1. Draw and name the structure of the compound. (2mks)
    2. To which homologous series does the compound C2H6O belong? (1mk)
  17. In the fractional distillation of liquid air explain how each of the following components are removed prior to liquifaction of air.
    1. Dust particles (1mk)
    2. Carbon (iv) Oxide (1mk)
    3. Water Vapour (1mk)
  18. A sample of water is suspected to contain Zinc ions and chloride ions. Give a test on how you can identify the presence of the ions. (3mks)
  19. The mass of a solution of salt of sodium chloride is 70.0g. This solution has 10.0g of sodium chloride dissolved in it. The solubility of this salt 30g/l00g of water at 25°C. 6.0g of sodium chloride salt are added to the solution at 25°C. How much sodium chloride will remain undissolved? (3mks)
  20. When 23 .2g of a hydrocarbon whose empirical formula is C2H5 was allowed to evaporate it occupied 9.6dm3 at R.T.P what is its molecular formula? (molar gas volume= 24dm3 at R.T.P) (3mks)
  21. Study the information below and answer the questions that follow.
     Number of carvbon atoms for molecule  Relative molecular mass of hydrocarbon 
     2  26
     3  40
     4  54
    1. Write the general formula of hydrocarbon in the table. ( ½mk)
    2. Predict the relative molecular mass of the hydrocarbon with 5 carbon atoms. ( ½mk)
    3. Determine the molecular formular of hydrocarbon in (b) and draw its structural formula (H=1, C=12). (2mks)
  22. X g of sodium hydroxide were dissolved in distilled water to make 100cm3 of solution. 50cm3 of this solution required 50cm3 of 2M nitric(v) acid for complete neutralization. Calculate the mass x of sodium hydroxide dissolved. (Na = 23, O = 16, H=1) (3mks)
  23. When the oxide of element H was heated with powdered carbon, the mixture glowed and carbon(IV)oxide gas was formed. When the experiment was repeated using the oxide of element J, there was no apparent reaction.
    1. Suggest one method that can be used to extract element J from its oxide. (1mk))
    2. Arrange the elements H, J and carbon in the order of their decreasing reactivity. (1mk)
  24. When a sample of concentrated sulphuric (IV) acid was left in an open beaker in a room for two days the volume was found to have increased slightly.
    1. What property of concentrated sulphuric (IV) acid is shown by the above reaction? (1mk)
    2. State one use of concentrated sulphuric(IV) acid that depends on the property namedabove. (1mk)
  25. The diagram below shows a set used to prepare gas Z. 
              ChemF42023MT1Q25
    1. Complete the diagram to show how gas z is collected. (1mk)
    2. Write an equation for the reaction between iron(II)sulphide and dilute hydrochloric acid. (1mk)
    3. Name substance x. (1mk)
  26. A beaker contained 75.0cm3 of acqueouscopper(ii) sulphate at 23.7°c, when a scrap iron was added to the solution the temperature rose to 29.3°c. if 5.83g of copper were deposited, calculate molar enthalpy change in kj/mol.(specific heat capacity of solution = 4.2Jg-1k-1, density of solution = 1g/cm3, Cu = 64) (2mks)
  27. Butane burns in air according to the equation below.
    2C4H10(g) + l3O2(g)—> 8 CO2(g) + 10H20(I)
    What volume of butane must be burnt in oxygen to give 11 g of carbon (IV) oxide at r.t.p? (Molar gas volume at r.t.p= 24.01; C= 12; 0= 16; H=1.0) (3mks)
  28. When magnesium ribbon is burnt in air, two compounds were formed, one of which is magnesium oxide:
    1. Name the other compound. (1mk)
    2. Describe an experiment to identify the solid you have named in (i) above           (1mk
  29. The structures below represent two cleaning agents M and P.
    ChemF42023MT1Q29
    Which cleaning agent would be most suitable for use with water containing calcium sulphate.  Give a reason. (2mks)


MARKING SCHEME

  1. A student set up the following apparatus in order to determine percentage of Oxygen by volume of air.
    ChemF42023MT1Q1
    1. State and explain the observations made on the moist iron wool at the end of theexperiment (after a week). (1mk)
      • The grey moist iron wool turns to red brown.
      • Iron, water & oxygen combine to form rust (hydrated iron III oxide)
    2. Give the expression of the percentage of oxygen by volume in the air in terms of the letter X, W,Y and Z in the diagram. (1mk)
      Z − y × 100
         x
    3. Write the formula of substance T. (1mk)
      Fe2O3.H2O
  2. The paper chromatography below shows the identification of unknown metal ion E and F. Thereference ions are K,L,M and N are shown. The experiment was done in ascending method.
    ChemF42023MT1Q2
    1. Name the ions in the mixture E. (1mk)
      • M & L
    2. Mixture F contains all the three ions. On the diagram show the chromatogram of  F. (1mk)
      ChemF42023MT1Ans2
    3. Comment on the ion N in the diagram. (1mk)
      • It is insoluble
  3. The following data gives pH values of solutions A, B and C.
     Solution  A   B   C 
     PH  13.6   6.9   1.3 
    1. Which solution named produce carbon (IV) oxide where reacted with a carbonate? (1mk)
      • C
    2. Write an ionic equation to show how the above reaction a(i) would be represented (1mk)
      CO32−(aq) + 2H+(aq) → CO2(g) + H2O(l)
    3. What would be the colour of solution A after adding a few drops of phenolphthalein? (1mk)
      • Pink
  4. Study the table below.
     Metal  Reaction with air   Reaction with water   Reaction with dilute acid 
     A  Reacts  Reacts slowly  Reacts
     B  Does not react  Does not react  Does not react
     C  Reacts  Reacts  Reacts vigorously
    1. Which metal is likely to be magnesium? (1mk)
    2. Which metal may be used as a cooking pot? (1mk)
    3. Arrange the metals in order of reacting starting with the most reactive. (1mk)
  5. An element Q has atomic number 3, relative atomic mass 6.94 and consists of two isotopes of mass 6.0 and 7.0.
    1. What is the mass number of the more abundant isotope of Q? Give a reason for your answer. (1mk)
      • The more abundant isotope of Q has mass number 6. The mass number of an isotope is the sum of the number of protons and neutrons in the nucleus of an atom. In the case of element Q, it has an atomic number of 3, which means it has 3 protons in its nucleus.
    2. Calculate the percentage abundant of the isotope which is more abundant. (2mks)
      percentage abundance =   (mass of isotope )    x 100
                                               relative atomic mass
      So, the percentage abundance of the more abundant isotope of Q is: (6.0 / 6.94) x 100 = 86.5%
      And 86.5% is the percentage abundance of this isotope.
  6. Below is a scheme of some reactions starting with but-2-ene. Study it and answer the questions that follows.
    ChemF42023MT1Q7
    1. Name Y, X and T.      (1 ½ mks)
    2. Give the name of the following organic compounds.                              ( 1 ½ mks)

      1. ChemF42023MT1Q7bi
      2.  
        ChemF42023MT1Q7bii
      3.  
        ChemF42023MT1Q7biii
  7. An element Y has the electronic configuration of 2.8.5.
    1. Write the formula of the most stable anion formed when element Y ionizes. (1mk)
    2. Write the formula of the compound formed by X and Y if the ion of x is represented as X2+ (1mk)
    3. Explain the difference between the atomic radius of element Y and its ionic radius. (1mk)
  8. Using dots(.) and crosses (x) diagram show he bonding in the following compounds.
    1. Lithium oxide ( Li= 3, O=8). (1mk)
      ChemF42023MT1Ans8a
    2. Carbon(II) oxide ( C =6, O=8) (1mk)
      ChemF42023MT1Ans8b
  9. Starting with zinc sulphate solution describe how a sample of zinc oxide can be obtained (3mks)
    • Prepare a solution of zinc sulphate (ZnSO4) by dissolving a known amount of zinc sulphate crystals in distilled water.
    • Heat the solution to a boiling point.
    • Slowly add a reducing agent like sodium hydroxide (NaOH) or sodium carbonate (Na2CO3) to the boiling zinc sulphate solution. As the reducing agent is added, it reacts with the zinc ions in the solution, converting them into zinc atoms.
    • The zinc atoms then react with oxygen from the air to form zinc oxide. The reaction can be represented as: Zn^2+(aq) + O2(g) → ZnO(s)
    • Continue heating and adding the reducing agent until the reaction is complete and no more zinc oxide forms.
    • Allow the solution to cool and then filter out any solid zinc oxide that has formed.
    • Wash the solid zinc oxide with distilled water to remove any impurities and dry it in a warm place.
    • The resulting solid zinc oxide can then be collected and used as a sample.
  10. The diagram below shows a set up that can be used for preparation of solid T in the laboratory.
    ChemF42023MT1Q10
    1. What condition must be included in the above apparatus for solid T to be formed? (1mk)
    2. Name the solid:
      1. Q…………………………………………………………………………………………. ( ½ mk)
      2. T………………………………………………………………………………………… ( ½ mk)
    3. Why is it possible to collect T as shown? (1mk)
  11. Below is a table showing elements in group II of the periodic table. Study it and answer the questions that below.
     Element  1st ionization energy (KJ/mol)   2nd ionization energy (KJ/mol) 
     Magnesium  900  1800 
     Beryllium  736  1450 
     Calcium  590   1150 
    1. What is ionization energy? (1mk)
    2. Explain why 2nd ionization energy of the elements is larger compared to 1st ionization. (2mks)
  12. Use the thermo chemical equations below to answer the questions that follow.
    C2H2 +  7/2O2(g)  →   2 CO2(g) + 3H2O(l)   ΔH = -1560KJ/MOL
    C(s) + O2(g)  →  CO2 (g)                              ΔH = -394KJ/MOL
    H2(g) + ½ O2(g)  →  H2O (g)                         ΔH= -286KJ/MOL

    Draw an energy cycle diagram to represent the information above and use it to calculate the heat of formation of ethyne (3mks)
  13. A student prepared ammonia gas and let it into a solution of zinc sulphate using the arrangement shown below.
    ChemF42023MT1Q13
    1. State and explain the observations that were made in a beaker.        (2mks)
      • White precipitate is formed which eventually dissolved with more ammonia gas. Zinc hydroxide ( white ppt) dissolve in excess ammonia.
    2. Write the ionic equation involving zinc ions.                                 (1mk)
      Zn2+(aq) + 2OH−(aq) → Zn[OH]2(g)
      Zn[OH]2(s) + NH3(aq) → [Zn(NH3)4]2+ + 2OH(aq)
  14. The melting point of phosphorus trichloride is 90°C while that of magnesium chloride in 715°C inmterms of structures and bonding explain the differences in their melting point. (3mks)
    • Magnesium chloride exists as giant ionic structure with strong ionic bonds - hence much energy to break phosphorus trichloride exist in molecules requiring less heat to break weak van-der waal's forces.
  15.  
    1. Name one property of Neon that makes it possible to be used in electric lamps. (1mk)
      • Unreactive hence provide unreactive environment.
    2. Name any other use of Argon other than in electric lamps. (1mk)
      • Welding and metal fabrication: Argon is used as a protective shield gas in welding and metal fabrication to prevent oxidation and other chemical reactions that can affect the quality of the finished product.
      • Food packaging: Argon is used to fill the space in food packaging, such as canned fruits and vegetables, to help preserve the freshness and quality of the food.
      • Glass manufacturing: Argon is used to create an inert atmosphere in the production of specialty glass, such as LCD and plasma display screens.
      • Pharmaceuticals: Argon is used in the production of some pharmaceuticals, such as in the manufacture of nitroglycerin for the treatment of heart conditions.
      • Auto Industry: Argon is used in the production of automotive airbags, as an inert gas to fill the airbag to deploy it in case of an accident.
      • Cryogenics: Argon is used as a coolant in cryogenic applications, such as in the production of superconducting magnets.
  16. A compound with molecular C2H6O reacts with sodium metal forming a basic solution.
    1. Draw and name the structure of the compound. (2mks)
      CH3CH2OH
      ChemF42023MT1Ans16 Ethanol
    2. To which homologous series does the compound C2H6O belong? (1mk)
      • Alkanols
  17. In the fractional distillation of liquid air explain how each of the following components are removed prior to liquifaction of air.
    1. Dust particles (1mk)
      • Removed by the nelectronic precipitation of the dust
    2. Carbon (iv) Oxide (1mk)
      • Passing the air through concentrated solution of sodium hydroxide.
    3. Water Vapour (1mk)
      • Freezing the air to −.25°C to remove water non form of ice
  18. A sample of water is suspected to contain Zinc ions and chloride ions. Give a test on how you can identify the presence of the ions. (3mks)
    • To the portion, add ammonia solution dropwise until in excess.
    • White precipitate dissolving in excess shows the presence of Zn2+
    • To another portion add Pb(NO3)2 solution and warm
    • White precipitates soluble on warming shows the presence of Cl ions
  19. The mass of a solution of salt of sodium chloride is 70.0g. This solution has 10.0g of sodium chloride dissolved in it. The solubility of this salt 30g/l00g of water at 25°C. 6.0g of sodium chloride salt are added to the solution at 25°C. How much sodium chloride will remain undissolved? (3mks)
    NaCl = 10.0g
    Total =  70.0g
    Watyer = 70 − 10
                = 60g
    100g of H2O contains 30g
      60g of H2O  →         ?
    60 × 30 = 18g
       100
    The solution should contain only 18g of salt
    8g should be added but 16g added
    ∴ 4g is in excess
    Undissloved = 4g of NaCl
  20. When 23 .2g of a hydrocarbon whose empirical formula is C2H5 was allowed to evaporate it occupied 9.6dm3 at R.T.P what is its molecular formula? (molar gas volume= 24dm3 at R.T.P) (3mks)
    9.6dm3 → 23.2g
    2.4dm3 → 24 × 23.2
                         9.6
                = 58g
    ,(C2H5)n = 58
    (24 + 5)n = 58
    29n = 58
    n = 58/29 
    n = 2
    (C2H5)2
    C4C10
  21. Study the information below and answer the questions that follow.
     Number of carvbon atoms for molecule  Relative molecular mass of hydrocarbon 
     2  26
     3  40
     4  54
    1. Write the general formula of hydrocarbon in the table. ( ½mk)
      • CnH2n−2
    2. Predict the relative molecular mass of the hydrocarbon with 5 carbon atoms. ( ½mk)
      54 + 14 = 68
    3. Determine the molecular formular of hydrocarbon in (b) and draw its structural formula (H=1, C=12). (2mks)
      C5H8
      ChemF42023MT1Ans21c
  22. X g of sodium hydroxide were dissolved in distilled water to make 100cm3 of solution. 50cm3 of this solution required 50cm3 of 2M nitric(v) acid for complete neutralization. Calculate the mass x of sodium hydroxide dissolved. (Na = 23, O = 16, H=1) (3mks)
    NaOH(aq) + HNO3(aq) → NaNO3(aq) + H2O(l)
    1000cm3 → 2 mols
      50cm3 →  50 × 2
                        1000
               = 0.1 mol
    NaOH : HNO3
        1           1
    ∴ NaOH in 50cm3
       = 0.1 mols
    50cm3 → 0.1mols
    1000cm3 → 100 × 0.1
                              50
                  = 0.2mols
    ⇒ 0.2 × 40 = 8g of NaOH dissolve in 100cm3
  23. When the oxide of element H was heated with powdered carbon, the mixture glowed and carbon(IV)oxide gas was formed. When the experiment was repeated using the oxide of element J, there was no apparent reaction.
    1. Suggest one method that can be used to extract element J from its oxide. (1mk)
      • Electrolysis of the molten oxide of J
    2. Arrange the elements H, J and carbon in the order of their decreasing reactivity. (1mk)
      • J, C, H
  24. When a sample of concentrated sulphuric (IV) acid was left in an open beaker in a room for two days the volume was found to have increased slightly.
    1. What property of concentrated sulphuric (IV) acid is shown by the above reaction? (1mk)
      • Hygroscopy
    2. State one use of concentrated sulphuric(IV) acid that depends on the property namedabove. (1mk)
      • Used as a drying sgent for most gases.
  25. The diagram below shows a set used to prepare gas Z. 
    ChemF42023MT1Ans24
    1. Complete the diagram to show how gas z is collected. (1mk)
    2. Write an equation for the reaction between iron(II)sulphide and dilute hydrochloric acid. (1mk)
      FeS(s) + 2HCl(aq) → FeCl2(aq) + H2S(g)
    3. Name substance x. (1mk)
      • Anhydrous Calcium Chloride
  26. A beaker contained 75.0cm3 of acqueous copper(ii) sulphate at 23.7°c, when a scrap iron was added to the solution the temperature rose to 29.3°c. if 5.83g of copper were deposited, calculate molar enthalpy change in kj/mol.(specific heat capacity of solution = 4.2Jg-1k-1, density of solution = 1g/cm3, Cu = 64) (2mks)
    Mass of CuSO4 = 75.0g
    ΔT = 5.6 K
    Q = 75 × 5.6 × 4.2
       = 1764J
      = 1.764 KJ
    5.83g of Cu → 1.764KJ
    64g of Cu → 64 × 1.764
                               5.83

    = 19.36 KJ mol−1
  27. Butane burns in air according to the equation below.
    2C4H10(g) + l3O2(g)—> 8 CO2(g) + 10H20(I)
    What volume of butane must be burnt in oxygen to give 11 g of carbon (IV) oxide at r.t.p? (Molar gas volume at r.t.p= 24.01; C= 12; 0= 16; H=1.0) (3mks)
    Moles of CO2
    11/44 = ¼ = 0.25mols
    lFrom mole ratios
    8 ⇒ 0.25mols
    2 ⇒ 2 × 0.25
               8
    0.0625mols of C4H10
    1 mole → 24.0litres
    0.0625mols → 0.0625 × 24
                                    1
     = 1.5litres
  28. When magnesium ribbon is burnt in air, two compounds were formed, one of which is magnesium oxide:
    1. Name the other compound. (1mk)
      • Magnesium Nitride Mg3N2
    2. Describe an experiment to identify the solid you have named in (i) above           (1mk)
      • Add drops of water to the solid, a gas with a pungent smell and fumes in contact with hydrogen chloride gas - confirms that it was a nitride of magnesium
  29. The structures below represent two cleaning agents M and P.
    ChemF42023MT1Q29
    Which cleaning agent would be most suitable for use with water containing calcium sulphate.  Give a reason. (2mks)
    • Cleansing agent P. Because it does not form insoluvble salt (scum) with calcium ions.
    • It forms soluble salt which lathers even in hard water.
Join our whatsapp group for latest updates

Download Chemistry Questions and Answers - Form 4 Mid Term 1 Exams 2023.


Tap Here to Download for 50/-




Why download?

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


Get on WhatsApp Download as PDF
.
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