Question

What quantity, in moles, of oxygen is consumed when 717.4 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)? H2(g) + O2(g) → H2O(l); ΔH° = –285.8 kJ

Answer 1

Answer: 2.51 moles of oxygen is consumed

Explanation:

Exothermic reaction : It is a type of chemical reaction where the energy is released into the surrounding. In the exothermic reaction, the energy of reactant are more than the energy of product.

In exothermic reaction, the change in enthalpy is, negative

The balanced chemical reaction is:

$2H_2(g)+O_2(g)\rightarrow 2H_2O(l)$ $\Delta H=-285.8kJ$

According to stoichiometry:

When 1 mole of oxygen is consumed , energy released = 285.8 kJ

285.8 kJ of energy is evolved when oxygen consumed = 1 mol

Thus whn 717.4 kJ of energy is evolved when oxygen consumed = $\frac{1}{285.8}\times 717.4=2.51$ moles

2.51 moles of oxygen is consumed