Question

How many moles of H₂ are required to give off -9551 kJ of heat in the following reaction?

Answer 1

Answer:

312.1 moles H₂ (4 sig.figs. based on -9551Kj value given).

Explanation:

Given N₂(g) + 3H₂(g) => 2NH₃(g);  ΔH° = -91.8Kj*

One mole of H₂ consumed will give -91.8Kj/3 = -30.6Kj/mole (exothermic)

moles H₂ consumed that gives -9551Kj (exothermic) = -9551Kj/-30.6Kj/mole H₂

= 312.124183moles H₂ (calculator answer) ≅ 312.1 moles H₂ (4 sig.figs. based on -9551Kj value given).

*Note: The ∆H° = -91.8 kJ/mol units should be only 'Kj' as the heat flow value applies to substances with three different coefficient values in the standard equation. FYI :-)