Question

Hess Law Problem? How do you find the change in enthalpy of water, magnesium and salt?

I have my equation below and we were told to find the Delta H_rxn for the reaction.

Please show a full explaination for a nice vote :)

2H₂O_(l)+Mg_(s)+2NaCl_(aq)----->2NaOH_(aq)+MgCl_2(aq)+H_2(g)

Answer 1

Solution :-

Balanced reaction equation

2H₂O_(l)+Mg_(s)+2NaCl_(aq)----->2NaOH_(aq)+MgCl_2(aq)+H_2(g)

Formula

Delta H rxn = sum of delta Hf product – sum of delta Hf reactant

                     = [(NaOH*2)+(MgCl2*1)+(H2*1)] –[ (H2O*2)+(Mg*1)+(NaCl*2)]

                    = [(-469.15*2)+(-800.12)+(0*1)] – [(-285.8*2)+(0*1)+(-407.27*2)]

                    = -352.28 kJ

Therefore the enthalpy change of the reaction is -352.28 kJ