Chemistry, How do I figure this out?

Question

When you add 0.205 g of sodium metal to an excess of hydrochloric acid, you find that 2130 J of heat are produced. What is the enthalpy of the reaction as written below?

                                            2Na(s)+2HCl(aq)-->2NaCl(aq)+H2(g)

 

Enthalpy Of Reaction: In kJ?

Answer 1

The enthalpy is the energy released in this case: -2.130 kJ

 

 

 

The enthalpy per mole of reactant is expressed in units of kJ/mol.

 

 

(0.205 g Na)(1 mole Na/22.990 g) = 0.00892 mole

 

 

ΔH = -2.130 kJ / 0.00892 mole = -238.8 kJ/mol

 

 

ΔH is negative because energy is released by the system.