Enthalpy changes and standard conditionsEdexcel A-Level Chemistry: Mind map

Exam questions on Enthalpy changes and standard conditions

1. Hydrogen reacts with oxygen to form water, both in fuel cells and in combustion engines. The standard enthalpy change of formation of liquid water is −286 kJ mol⁻¹.
   Define the term standard enthalpy change of formation.2 marks
2. A company makes two types of instant pack. The hot pack contains calcium oxide, which reacts with water in an exothermic reaction. The cold pack contains ammonium nitrate, which dissolves in water in an endothermic process with ΔH = +25.7 kJ per mole of ammonium nitrate.
   A cold pack contains 32.0 g of ammonium nitrate, NH₄NO₃ (Mr = 80.0). Calculate the energy absorbed, in kJ, when all of it dissolves.2 marks
3. The standard enthalpy change of combustion of ethanol is −1367 kJ mol⁻¹, and the standard enthalpy change of neutralisation for a strong acid reacting with a strong alkali is −57 kJ mol⁻¹.
   Define the term standard enthalpy change of combustion and write the equation, including state symbols, for the standard enthalpy change of combustion of ethanol.3 marks