Question

____ 5. Use the following information to answer the next question.


When placed in acid, magnesium metal reacts and forms hydrogen gas:
Mg(s) + HCl(aq)  MgCl2(aq) + H2(g) H = -56.5 kJ/mol

If HP denotes the enthalpy of products and Hr denotes the enthalpy of reactants, then
a. HP > Hr
b. HP < Hr
c. HP = Hr
d. HP Hr
e. impossible to tell from given data

Answer 1

b. HP < Hr

Explanation: ΔH = HP - Hr = -56.5 kJ/mol, so the products have 56.5 kJ/mol less enthalpy than the reactants.