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Enthalpy changes

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Question 21

A student carries out an experiment in the laboratory to determine the enthalpy change of neutralisation, ΔneutH\Delta_{\text{neut}}HΔneut​H, for the reaction between aqueous sulfuric acid, H2SO4\text{H}_2\text{SO}_4H2​SO4​, and aqueous lithium hydroxide, LiOH\text{LiOH}LiOH.

The equation for this neutralisation is:

H2SO4(aq)+2LiOH(aq)→Li2SO4(aq)+2H2O(l) \text{H}_2\text{SO}_4\text{(aq)} + 2\text{LiOH(aq)} \rightarrow \text{Li}_2\text{SO}_4\text{(aq)} + 2\text{H}_2\text{O(l)} H2​SO4​(aq)+2LiOH(aq)→Li2​SO4​(aq)+2H2​O(l)

The student follows this method:

  • Add 40.0 cm340.0\text{ cm}^340.0 cm3 of 0.300 mol dm−30.300\text{ mol dm}^{-3}0.300 mol dm−3 sulfuric acid to a polystyrene cup.
  • Measure out 60.0 cm360.0\text{ cm}^360.0 cm3 of 0.600 mol dm−30.600\text{ mol dm}^{-3}0.600 mol dm−3 LiOH(aq)\text{LiOH(aq)}LiOH(aq), which is in excess.
  • Measure the temperature of both solutions.
  • Add the LiOH(aq)\text{LiOH(aq)}LiOH(aq) to the sulfuric acid in the polystyrene cup, stir the mixture, and record the maximum temperature.

Temperature readings:

  • Maximum temperature of mixture: 22.9 ∘C22.9\text{ }^\circ\text{C}22.9 ∘C
  • Initial temperature of both solutions: 19.6 ∘C19.6\text{ }^\circ\text{C}19.6 ∘C

Calculate a value for the enthalpy change of neutralisation, ΔneutH\Delta_{\text{neut}}HΔneut​H, in kJ mol−1\text{kJ mol}^{-1}kJ mol−1.

Assume that the density of all solutions is 1.00 g cm−31.00\text{ g cm}^{-3}1.00 g cm−3 and the specific heat capacity, ccc, of the reaction mixture is the same as for water, 4.18 J g−1 K−14.18\text{ J g}^{-1}\text{ K}^{-1}4.18 J g−1 K−1. Give your answer to 3 significant figures.

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Enthalpy changes Questions

  1. A Level
  2. /Chemistry
  3. /Enthalpy changes