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2 marksMole Concept

CSEC Chemistry · January 2011 · Paper 2 · Question 1(a)(vi)

An experiment is conducted to determine the end point of an acid-base reaction by measuring temperature changes when different volumes of a strong acid react with a strong base. Table 1 shows volumes of sulfuric acid reacting with 25 cm³ of 2.0 mol dm⁻³ sodium hydroxide and the resulting temperature changes. Figure 1 shows thermometer readings for the addition of 10 cm³ and 20 cm³ of H₂SO₄.

Write a balanced equation for this reaction.

This question uses a figure or table from the paper — you'll see it when you practise.

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Other parts of this question

  1. 1(a)(i)Differentiate between a 'strong acid' and a 'weak acid'.[2 marks]
  2. 1(a)(ii)Suggest ONE other base that could be used instead of NaOH.[1 mark]
  3. 1(a)(iii)Using the thermometer readings in Figure 1, complete Table 1 by recording the temperature for the addition of 10 cm³ and 20 cm³ of the H₂SO₄.[2 marks]
  4. 1(a)(iv)Plot the points for temperature against volume of acid added using the axes on page 3.[3 marks]
  5. 1(a)(v)Draw the TWO lines of best fit through the points in (iv) above where the temperature is increasing and where the temperature is decreasing and hence determine…[3 marks]
  6. 1(a)(vii)Calculate the number of moles of NaOH used in the reaction.[1 mark]
  7. 1(a)(viii)Calculate the concentration of H₂SO₄ in mol dm⁻³.[2 marks]
  8. 1(b)(i)Identify Solution X.[1 mark]
  9. 1(b)(ii)Identify ONE flaw in the procedure that Paul used for carrying out EACH test.[2 marks]
  10. 1(b)(iii)Write a balanced equation for the reaction occurring in Tube 1. Balanced equation:[2 marks]
  11. 1(b)(iv)Explain why nitric acid instead of sulphuric acid is used in the experiment in Tube 1 in order to obtain a positive test result.[4 marks]

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