Chemistry Questions and Answers - Form 2 End Term 1 Exams 2022

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QUESTIONS

Answer all the questions in the spaces provided.

  1. The diagram below shows how muddy water can be made clean. Study it and answer the
    questions that follow.
    1 AUYGUYDAD
    1. Name the apparatus labeled X. (1 mk)
    2. Give a reason why the clean water took a long time to drop into the boiling tube.(2 mks).
  2. In the experiment to study the effect of heat on naphthalene the following set up was used.
    2 uyugdyada
    1. Name the apparatus labeled A and B. (2 mks)
      A -
      B –
    2. The curve shown below was obtained when solid naphthalene was heated to boiling.
      1. Explain in molecular terms the changes occurring in portions :- (2 mks)
        AB –
        DE - 
      2. What is the significance of portion BC? (1 mk)
  3. In the process of separating or extracting oil from castor oil seeds in the laboratory, students from Anestar schools crushed the seed sand then added propanone (acetone) instead of water.
    1. Why were the seeds first crushed? (1 mk)
    2. Explain how the oil can be separated from propanone. (2 mks)
  4. Name the method of separation that can most suitably be used to separate the following mixtures.
    1. Gasoline from petroleum - (1 mks)
    2. Benzoic acid from potassium carbonate - (1 mk)
    3. Oil from Cashew nuts - (1 mk)
  5.                                  
    1. What is the role of the following parts during fractional distillation of a mixture of water and ethanol.
      1. Fractionating column - (1 mk)
      2. Glass beads in the fractionating column (1 mk)
    2. State any one application of the fractional distillation process. (2 mks)
  6. The figure below shows a section of the periodic table. The letters do not represent the actual symbols of the elements.
    5 auigduygaud
    1. Give the name of the family of the elements to which M belongs. (1 mk)
    2. Write down the electronic configuration of the stable ion of elements. (2 mks)
      1. L –
      2. P
    3. Give one use of elements. (2 mks)
    4. What is the structure of element J. (1 mk)
    5. With explanation, compare the atomic radius of O and P. (2 mks)
    6. What is the family name given to the group number to which element E belongs to? (1 mk)
    7. With reasons, compare the atomic radius of elements B and A. (2 mks)
    8. State two industrial use of element B. (2 mks)
    9. With reason compare the reactivity of E and A. (3 mks)
    10. Write down the formula of the compound formed when D and A react. (1 mk)
    11. What type of bond is formed when element E reacts with oxygen? Give a reason for your answer. (2 mks)
    12. Which is the most reactive non-metal? Explain. (2 mks)
  7.                            
    1. What is an isotope? (1 mk)
    2. An element Q consists of 3 isotopes of mass 28, 29 and 30 and percentage abundance of 92.2%, 4.7% and 3.1% respectively. Determine the relative atomic mass of the element. (3 mks)
  8. Study the table below and answer the questions that follow. The letters do not represent the actual symbols of the elements.
    Formula of Ion   Electronic configuration. 
     E2+   2
     D  2.8
     C+  2.8.8
     B3+   2.8
     A2+  2.8
    1. Select the elements found in:-
      1. The same group - (1 mk)
      2. Period three - (1 mk)
  9. Complete the following equations and balance them off. (2 mks)
    1. K + O2 →
    2. Ca + O2 →
    3. Na + O2  →
    4. Na(s) + HCl(aq)  →
    5. Mg + O2  →
    6. Mg + H2SO4  →
    7. Ca + HNO3  →
    8. HCl + NaOH  →
    9. Ca + H2O  →
    10. Al + O2  →
  10. Using dots and crosses to represent electrons, draw the structures of the following. (4 mks)
    1. H2
    2. Cl2

MARKING SCHEME

Answer all the questions in the spaces provided.

  1. The diagram below shows how muddy water can be made clean. Study it and answer the
    questions that follow.
    1 AUYGUYDAD
    1. Name the apparatus labeled X. (1 mk)
      filter funnel
    2. Give a reason why the clean water took a long time to drop into the boiling tube.(2 mks).
      the air trapped inside prevented water going through those tubes. no space is provided for air to exit
    3. Name the method of separation shown above
      filtration
  2. In the experiment to study the effect of heat on naphthalene the following set up was used.
    2 uyugdyada
    1. Name the apparatus labeled A and B. (2 mks)
      A - thermometer
      B –  beaker
    2. The curve shown below was obtained when solid naphthalene was heated to boiling.
      1. Explain in molecular terms the changes occurring in portions :- (2 mks)
        AB – temperature increases steadily as napthalene absorbs heat energy. This increases the kinetic energy of the particles making them vibrate more vigorously
        DE - energy is used to overcome intramolecular forces holding the liquid particles together. boiling occurs.
      2. What is the significance of portion BC? (1 mk)
        melting point of wax
  3. In the process of separating or extracting oil from castor oil seeds in the laboratory, students from Anestar schools crushed the seed sand then added propanone (acetone) instead of water.
    1. Why were the seeds first crushed? (1 mk)
      to increase the surface area of concentrate with propane (solvent)
    2. Explain how the oil can be separated from propanone. (2 mks)
      evaporation because propane being more volatile than oil, will evaporate first leaving the oil.
  4. Name the method of separation that can most suitably be used to separate the following mixtures.
    1. Gasoline from petroleum - (1 mks)
      fractional distillation
    2. Benzoic acid from potassium carbonate - (1 mk)
      sublimation
    3. Oil from Cashew nuts - (1 mk)
      solvent extraction
  5.                                  
    1. What is the role of the following parts during fractional distillation of a mixture of water and ethanol.
      1. Fractionating column - (1 mk)
        allows vapour of liquid whose boiling point has been reached to flow back to the flask
      2. Glass beads in the fractionating column (1 mk)
        increases surface area for condensation
    2. State any one application of the fractional distillation process. (2 mks)
      - distillation of crude oil to obtain fractions distillation
      - distillation of liquid air to obtain nitrogen oxygen and argon
  6. The figure below shows a section of the periodic table. The letters do not represent the actual symbols of the elements.
    5 auigduygaud
    1. Give the name of the family of the elements to which M belongs. (1 mk)
      halogens
    2. Write down the electronic configuration of the stable ion of elements. (2 mks)
      1. L – 2.8.8
      2. P - 2.8.8
    3. Give one use of elements. (2 mks)
      A -  weather baloons, hydrogenation, rocket fuel, welding
      M - bleaching agent, manufacture of ammonia
    4. What is the structure of element J. (1 mk)
      giant atomic structure
    5. With explanation, compare the atomic radius of O and P. (2 mks)
      G has a lager atomic radius than H because H has many protons, leads to high nuclear change resulting to strong nuclear pull of attracting other electrons closer to their nuclear 
    6. What is the family name given to the group number to which element E belongs to? (1 mk)
      alkaline (earth metals)
    7. With reasons, compare the atomic radius of elements B and A. (2 mks)
      B is smaller than A or  A is larger than B or B has higher nuclear charge than A which pulls electrons closer to the nucleus
    8. State two industrial use of element B. (2 mks)
      aeroplane on vehicle body constrtuction
      - making wires for overhead cables for transmission
    9. With reason compare the reactivity of E and A. (3 mks)
      - A is more reactive than E or E is less reactive than A
      - A loses outer electrons readily than E because the outer electrons of A are closely attracted since they are further from the attraction force of the nucleus
    10. Write down the formula of the compound formed when D and A react. (1 mk)
      AD2 and not D2A
    11. What type of bond is formed when element E reacts with oxygen? Give a reason for your answer. (2 mks)
      ionic or electrovalent bond
      E is a metal and loses outer electrons to o xygen
    12. Which is the most reactive non-metal? Explain. (2 mks)
      O - it loses electrons readily since it has the longest atomic radius
  7.                            
    1. What is an isotope? (1 mk)
      - is one of the atoms of the same element having a different mass number from the rest, but same atomic number with others of the same element
    2. An element Q consists of 3 isotopes of mass 28, 29 and 30 and percentage abundance of 92.2%, 4.7% and 3.1% respectively. Determine the relative atomic mass of the element. (3 mks)
      (92.2 × 28 + 4.7 × 29 + 3.1 × 30)
             100          100            100
      = 28.11
  8. Study the table below and answer the questions that follow. The letters do not represent the actual symbols of the elements.
    Formula of Ion   Electronic configuration. 
     E2+   2
     D  2.8
     C+  2.8.8
     B3+   2.8
     A2+  2.8
    1. Select the elements found in:-
      1. The same group - (1 mk)
        E and A
      2. Period three - (1 mk)
        C, B and A
  9. Complete the following equations and balance them off. (2 mks)
    1. 4K + O2 → 2K2O
    2. 2Ca + O2 → 2CaO
    3. 2Na + O2  → 2Na2O
    4. 2Na(s) + 2HCl(aq)  → 2NaCl + H2
    5. 2Mg + O2  → 2MgO
    6. Mg + H2SO4  → MgSO4 + H2
    7. Ca + 2HNO3  → Ca(NO3)2 + H2
    8. HCl + NaOH  → NaCl + H2O
    9. Ca + H2O  → Ca(OH)2
    10. 4Al + 3O2  → 2Al2O3
  10. Using dots and crosses to represent electrons, draw the structures of the following. (4 mks)
    1. H2
      h2 aiuhdiuad
    2. Cl2
      cl auygduygad

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