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3 marksEnergetics

CSEC Chemistry · January 2021 · Paper 2 · Question 1(a)

An experiment to determine the concentration of sodium hydroxide in g dm⁻³ using thermometric titration with 0.10 M H₂SO₄. Aliquots of 5 cm³ of H₂SO₄ are added to 25 cm³ NaOH in a styrofoam cup, measuring temperature after each addition.

Using the thermometer readings in Figure 1, complete Table 1 by recording the temperatures for additions of 5 cm³, 15 cm³ and 25 cm³ of H₂SO₄.

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Other parts of this question

  1. 1(b)(i)Plot the graph of temperature against volume of acid added using the axes provided in Figure 2.[4 marks]
  2. 1(b)(ii)Draw two lines of best fit through the points on the graph: one where temperature is increasing and one where temperature is decreasing.[2 marks]
  3. 1(b)(iii)Show the end point of the reaction on the graph and record the corresponding volume.[2 marks]
  4. 1(c)Distinguish between a 'strong acid' and a 'weak acid'.[2 marks]
  5. 1(d)Write a balanced chemical equation for the reaction between NaOH and H₂SO₄.[2 marks]
  6. 1(e)Calculate the number of moles of H₂SO₄ used in the reaction.[2 marks]
  7. 1(f)Calculate the number of moles of NaOH in 25 cm³ of the solution.[2 marks]
  8. 1(g)Calculate the concentration of NaOH, in mol dm⁻³.[2 marks]
  9. 1(h)Calculate the concentration of NaOH in g dm⁻³, given the molar mass of NaOH = 40 g mol⁻¹.[1 mark]
  10. 1(i)State whether the reaction in the styrofoam cup was exothermic or endothermic and explain your answer.[2 marks]
  11. 1(j)State ONE safety precaution that should have been taken during the experiment.[1 mark]

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