Measuring enthalpy changesEdexcel A-Level Chemistry: Mind map

Exam questions on Measuring enthalpy changes

1. A student measures the enthalpy change of combustion of propan-1-ol (Mr = 60.0) using a spirit burner to heat 150 g of water in a copper can. The temperature of the water rises by 28.0 K when 0.60 g of propan-1-ol is burned. The specific heat capacity of water is 4.18 J g⁻¹ K⁻¹.
   The data book value is −2021 kJ mol⁻¹. Give two reasons why the experimental value is less exothermic than this.2 marks
2. A student measures the enthalpy change of neutralisation by mixing 25.0 cm³ of 1.00 mol dm⁻³ hydrochloric acid with 25.0 cm³ of 1.00 mol dm⁻³ sodium hydroxide solution in an insulated polystyrene cup. The temperature rises from 20.5 °C to 27.2 °C. Assume the solutions have density 1.00 g cm⁻³ and specific heat capacity 4.18 J g⁻¹ K⁻¹.
   Calculate the enthalpy change of neutralisation, in kJ mol⁻¹, including the sign.2 marks
3. A student measures the enthalpy change for Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s). She adds 2.00 g of zinc powder (Ar = 65.4) to 50.0 cm³ of 0.500 mol dm⁻³ copper(II) sulfate solution in a polystyrene cup and stirs. The temperature rises from 19.8 °C to 45.6 °C. Assume the solution has density 1.00 g cm⁻³ and specific heat capacity 4.18 J g⁻¹ K⁻¹.
   Calculate the amount, in mol, of copper(II) ions in the solution and the energy transferred to the solution, in kJ.3 marks