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Chemistry — Model Question Paper 2

Chemistry · Kerala SSLC (Class 10) · English Medium · SSLC 2027 pattern · English Medium · 40 marks · 90 min + 15 min cool-off

Section A

Questions 1–4 carry 1 score each. Answer all.

  1. The subshell electron configuration of an element is 1s² 2s² 2p⁶ 3s² 3p³. What is its position in the periodic table? [1 mark]
    • Period 3, Group 5
    • Period 2, Group 15
    • Period 3, Group 15
    • Period 5, Group 3
  2. Assertion (A): Teflon is used to coat the inner surface of non-stick cookware. Reason (R): Teflon is a condensation polymer formed from tetrafluoroethene. Which of the following is correct? [1 mark]
    • Both (A) and (R) are correct, and (R) is the correct explanation of (A).
    • Both (A) and (R) are correct, but (R) is not the correct explanation of (A).
    • (A) is correct, but (R) is not correct.
    • (A) is not correct, but (R) is correct.
  3. Match the ores in column A with their chemical formulae in column B. A (X) Bauxite (Y) Haematite (Z) Zinc blende B (i) Fe₂O₃ (ii) ZnS (iii) Al₂O₃·2H₂O (iv) ZnCO₃ Choose the correct combination. [1 mark]
    • X–(iii), Y–(ii), Z–(iv)
    • X–(i), Y–(iii), Z–(ii)
    • X–(iii), Y–(i), Z–(iv)
    • X–(iii), Y–(i), Z–(ii)
  4. Some statements about gases are given. (i) At constant temperature, if the pressure on a fixed mass of gas is halved, its volume doubles. (ii) At STP, one mole of any gas occupies 22.4 L. (iii) At constant pressure, the volume of a gas is directly proportional to its temperature in degrees Celsius. Which of the following is correct? [1 mark]
    • Statements (i) and (iii) are correct, but (ii) is not correct.
    • Statements (i) and (ii) are correct, but (iii) is not correct.
    • Only statement (iii) is correct.
    • Statements (i), (ii) and (iii) are correct.

Section B

Questions 5–11 carry 2 scores each. Two questions from 5 to 11 have a choice — answer (A) or (B).

  1. The structural formula of an organic compound is CH₃–CH₂–CH₂–CH₂–COOH. [2 marks]
    • (a) Write its IUPAC name.
    • (b) Its molecular formula is C₅H₁₀O₂. An ester with the same molecular formula is a functional group isomer of it. Write the structural formula and IUPAC name of one such ester.
  2. Oxalic acid (H₂C₂O₄, HOOC–COOH) is found in spinach and tomato. [2 marks]
    • (a) What is the basicity of oxalic acid? What type of acid is it called based on this?
    • (b) Write the equation of ionisation of oxalic acid.
  3. (A) Iron (atomic number 26) forms the oxide Fe₂O₃. [2 marks]
    • (a) Find the oxidation state of iron in Fe₂O₃.
    • (b) Write the subshell electron configuration of the iron ion in Fe₂O₃.

    OR

    (B) The subshell electron configuration of an element Q ends in 3p⁴. (The symbol is not real.)

  4. The figure shows an arrangement to coat a copper spoon (B) with silver. [2 marks]
    • (a) What should electrode A be made of? Is A the anode or the cathode?
    • (b) Suggest a suitable solution for X and write the reaction that takes place at B.
  5. Ethanol is manufactured industrially from molasses. [2 marks]
    • (a) Name the enzymes in yeast that convert (i) sugar into glucose and fructose, and (ii) glucose and fructose into ethanol.
    • (b) Rectified spirit meant for industrial use is mixed with substances such as methanol or pyridine. What is the product called, and why is this done?
  6. Calamine (ZnCO₃) is an ore of zinc. [2 marks]
    • (a) Name the process used to convert the concentrated calamine into zinc oxide, and write its chemical equation.
    • (b) Write the equation for the reduction of zinc oxide with coke. Why does zinc come out of the furnace as a vapour?
  7. (A) A syringe holds 600 mL of air at 1 atm pressure. Keeping the temperature constant, the piston is pushed in until the volume becomes 200 mL. [2 marks]
    • (a) Which gas law applies here? Write its mathematical form.
    • (b) Find the new pressure of the air.

    OR

    (B) At a certain temperature and pressure, 5 L of nitrogen gas contains N molecules.

Section C

Questions 12–17 carry 3 scores each. Two questions from 12 to 17 have a choice — answer (A) or (B).

  1. (A) The structural formula of a compound is CH₃–CH₂–CH₂–CHO. [3 marks]
    • (a) Write its IUPAC name.
    • (b) Write the structural formula and IUPAC name of a functional group isomer of this compound.
    • (c) Write the structural formula and IUPAC name of a chain isomer of this compound.

    OR

    (B) The structural formula of an alkene is CH₂=CH–CH₂–CH₃.

  2. Polymers such as polythene, PVC and nylon 66 are part of daily life. [3 marks]
    • (a) Write the chemical equation for the polymerisation of ethene.
    • (b) Name the polymer formed from vinyl chloride (CH₂=CHCl) and give one use of it.
    • (c) Nylon 66 is made from adipic acid and hexamethylenediamine. Why is it called a condensation polymer?
  3. Hydrogen burns in oxygen to form water: 2H₂ + O₂ → 2H₂O 8 g of hydrogen is burnt completely. (Atomic mass: H = 1, O = 16) [3 marks]
    • (a) How many moles of hydrogen are burnt?
    • (b) Find the volume of oxygen needed at STP.
    • (c) Find the mass of water formed.
  4. (A) A concentrated solution of sodium chloride is electrolysed using platinum electrodes. A few drops of phenolphthalein are added to the solution. [3 marks]
    • (a) Which gas is liberated at the anode? Write the equation.
    • (b) Hydrogen, not sodium, is formed at the cathode. Why? Write the equation of the reaction at the cathode.
    • (c) The solution near the cathode turns pink. Why?

    OR

    (B) A galvanic cell is made with a zinc rod in ZnSO₄ solution and a silver rod in AgNO₃ solution, joined by a salt bridge.

  5. Haematite, coke and limestone are fed into a blast furnace to produce iron. [3 marks]
    • (a) Write the chemical equation for the reduction of haematite by carbon monoxide.
    • (b) The ore contains silica (SiO₂) as an impurity. How is it removed? Write the equation for slag formation.
    • (c) Pig iron from the blast furnace is converted into steel. What is the main difference between pig iron and steel in composition?
  6. The atomic numbers of three elements are given. (The symbols are not real.) P = 19, Q = 29, R = 35 [3 marks]
    • (a) Write the subshell electron configuration of Q and name its block.
    • (b) Find the period and group of R.
    • (c) Write the chemical formula of the compound formed between P and R.

Section D

Question 18 carries 4 scores. It has a choice — answer (A) or (B).

  1. (A) Ammonia is manufactured on a large scale by the Haber process. The forward reaction is exothermic. [4 marks]
    • (a) Write the balanced chemical equation for this process and name the catalyst.
    • (b) Using Le Chatelier's principle, suggest how the pressure and the temperature should be changed to get more ammonia.
    • (c) Concentrated sulphuric acid is a good drying agent, but it is not used to dry ammonia. Why?
    • (d) Name one nitrogenous fertilizer made from ammonia and write its chemical formula.

    OR

    (B) Sodium hydroxide and calcium hydroxide are important alkalis, and they form salts with acids.

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