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Engineering Science Practice Assessment: Paper 2

This section focuses on applied chemistry and mechanics, including stoichiometry, electrochemistry, and motion analysis.

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QUESTION 1

The decomposition by water of Calcium carbide into its component parts produces slaked lime and a combustible fuel which is used in the Oxyacetylene fuel, and also used in the Oxyacetylene burner.

$CaC_2 + H_2O \longrightarrow Ca(OH)_2 + \text{gas}$

(Given: Ca=40g/mol, C=12g/mol, H=1, O=16g/mol)

• (a)

  • (i) Name the gas obtained and give its formula. (2 marks)

  • (ii) Balance the equation of the chemical reaction. (2 marks)

  • (iii) Calculate the mass of slaked lime obtained from 2.5g of calcium carbide. (2 marks)

• (b) A current of 2A is passed through molten lithium hydride for 15 minutes. (Molar Volume of gas is $2400\text{ cm}^3$ at r.t.p) Calculate:

  • (i) The number of Faradays used in this experiment. (2 marks)

  • (ii) The number of moles of Lithium atoms produced. (2 marks)

  • (iii) The volume of gas produced at room temperature and atmospheric pressure (r.t.p). (2 marks)

• (c)

  • (i) Explain how catalytic cracking helps to achieve this increase production of high-octane petrol. (2 marks)

  • (ii) Name one environmental problem that may arise from increased petrol consumption. (1 mark)

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OR 1. d, e, f

• (d)

  • (i) Explain the difference between a strong acid and a weak acid, giving an example of each. (2 marks)

  • (iii) Calcium carbonate reacts with Hydrochloric acid. Write the equation of this reaction and name the gas. (3 marks)

• (e) The element barium (Ba) is a group II element of the periodic table. An atom of barium is represented as $^{137}_{56}Ba$.

  • (i) What is the atomic number of barium, and what does it represent? (2 marks)

  • (ii) How many neutrons are present in an atom of barium-137? (1 mark)

  • (iii) How many electrons are there in the outer most shell of barium? (1 mark)

  • (iv) Why does barium form a $Ba^{2+}$ ion rather than $Ba^+$? (2 marks)

• (f) 15 g of magnesium reacts with excess oxygen to form magnesium oxide.

  • (i) Calculate the moles of magnesium used. (2 marks)

  • (ii) Write the equation to show the formation of magnesium oxide and determine how many moles of MgO are formed. (2 marks)

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QUESTION 2

(a) The diagram below represents a distance (m) – time (s) graph of a car’s journey.

(Referencing Figure 1: OA is a curve, AB is a straight diagonal line, BC is a horizontal line at 900m)

• (i) Describe briefly, the motion of the car represented by OA, AB, and BC. (3 marks)

• (ii) What is the car’s average speed during the first 10s? (2 marks)

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END!