When 0.365 g of sodium metal is added to an excess of hydrochloric acid, 3790 J of heat are produced. What is the enthalpy of the reaction as written? 2Na(s)+2HCl(aq)⟶2NaCl(aq)+H2(g)

Answer 1

mols Na = 0.365 g x 1 mol Na / 23.0 g = 0.01587 mols

2Na + 2HCl ==> 2NaCl + H₂ ... balanced equation

3790 J / 0.01587 mols x 2 mols Na x 1 kJ / 1000 J = 477.6 kJ/mol = -478 kJ

There is a minus sign in front of the answer since heat is PRODUCED making the reaction exothermic.