Question 4.20: Heat of Reaction The combustion of 1 mol of methane gas, CH4...
Heat of Reaction
The combustion of 1 mol of methane gas, \text{CH}_{4}, to carbon dioxide and water is an exothermic reaction that liberates 191.7 kcal.
\text{CH}_{4}\text{(g)} + \text{O}_{2}\text{(g)} \longrightarrow \text{CO}_{2}\text{(g)} + 2\text{H}_{2}\text{O(g)} + 191.7\ \text{kcal}How much heat is liberated when 4.52 g of \text{CH}_{4} undergoes combustion?
Strategy
According to the balanced chemical equation, we know that 1 mol \text{CH}_{4} = 191.7 kcal. Therefore, we convert the grams of \text{CH}_{4} to moles and then apply the heat conversion factor.
Therefore, we conclude that when 4.52 g of \text{CH}_{4} undergoes combustion, 54.2 kcal of heat is liberated.
■ Quick Check 4.20
Solid iron and oxygen gas react to form solid iron(III) oxide, liberating 406.3 kcal of heat according to the following balanced chemical equation. 4\text{Fe(s)} + 3\text{O}_{2}\text{(g)} \longrightarrow 2\text{Fe}_{2}\text{O}_{3}\text{(s)} + 406.3\ \text{kcal}. How many kcal of heat are liberated when 2.50 g of Fe reacts?