ΔHf for the following reaction: 2NaCl (aq) + H2SO4 (aq) ----> 2HCl (aq)+ Na2SO4

Answer 1

To calculate the heat of formation for the given reaction you must use the table provided in the back of your textbook since these values do change by author and can provide a different answer.

However, the general equation to use will be the following:

ΔHoreaction=∑ΔHof(products)−∑ΔHof(Reactants)

this means you'll do products-reactants using the stiochemetric coefficient in the balanced equation.