Reactivity 3.1 – Proton transfer reactions

R3.1.1 & R3.1.2 – Brønsted-Lowry acids and bases

📌 Transferring H+ ions

ΔH°= ∑(ΔHc° reactants) − ∑(ΔHc°products)

  • The Brønsted-Lowry acid base theory defines acids and bases as substances based on the exhcange of protons (aka H+ ions)
  • An acid can be defined as a proton donor while a base is defined as a proton acceptor
  • This theory also suggests that every acid has a ‘conjugate base’ and every base has a ‘conjugate acid’
  • A conjugate is a substance differing by exacatly one H+ ion
  • A Brønsted-Lowry acid would be a reactant with the general formula XH while it’s conjugate base would be X–
  • Similarly, a Brønsted-Lowry base would be a reactant with the general formula Y while it’s conjugate acid would be YH

EXAMPLE :

Calculate the enthalpy of formation of glucose using the enthalpies given in section 14 of the data booklet

  1. 6C + 6H2 + 3O2 → (1)C6H12O2
  2. [6(-394) + 6(-286) + 3(0)] – [1(-2803)] = -1277 kJ mol-1

Therefore, the enthalpy of formation of one mole of glucose is -1277 kJ mol-1 (using the enthalpy of combustion)