Question

Explain why the enthalpy change of neutralisation of one mole of sulfuric acid, H2SO4, is not the standard enthalpy change of neutralisation.

Answer 1

If we compare the enthalpy change of neutralization with the standard evolution of neutralization, it becomes clear that they are not equivalent. The enthalpy change of neutralization of one mole of sulfuric acid, H2SO4, is not the standard enthalpy change of neutralization. This is because for every mole of H2SO4 being neutralized, 2 moles of hydrogen ions (H+) are needed to combine and become water. In other words, two moles in total are required to break down a single mole of H2SO4. This is not the same as the usual scenario, which involves one mole of acid being neutralized and one mole of the base being added. One mole of sulfuric acid H2SO4 has an enthalpy change of -99.2 kJ compared with 1 mole of water which has a value of +393.5 kJ (all values at 298 kPa). Note that this is the standard enthalpy change of dissolution. It will be referred to as standard enthalpy change of neutralization.

Note that this is the standard enthalpy change of dissolution. It will be referred to as standard enthalpy change of neutralization.