Answer:
[tex]\text{1540 kJ}[/tex]
Explanation:
1. Gather all the information in one place
Mᵣ: 2.016
H₂ + ½O₂ ⟶ H₂O + 148.1 kJ
m/g: 21.9
2. Moles of H₂
[tex]n = \text{21.9 g H}_{2} \times \dfrac{\text{1 mol H}_{2}}{\text{2.016 g H}_{2}} = \text{10.86 mol H}_{2}[/tex]
3. Calculate ΔH
Treat the heat AS IF it were a reactant or product. In this case, the reaction is exothermic, so the heat is a product.
In effect, you have 148.1 mol of "kJ"s for each mole of hydrogen and
[tex]\Delta \text{H} = \text{10.86 mol H}_{2} \times \dfrac{\text{141.8 kJ}}{\text{1 mol H}_{2}} = \textbf{1540 kJ}[/tex]
