Question

When Fe2O3(s) reacts with H2(g) according to the following reaction, 2.00 kJ of energy are evolved for each mole of Fe2O3(s) that reacts. Complete the following thermochemical equation. 3Fe2O3(s) + H2(g)2Fe3O4(s) + H2O(g)

Answer 1

Answer:

3 Fe₂O₃(s) + H₂(g) ⇒ 2 Fe₃O₄(s) + H₂O(g)    ΔH° = -6.00 kJ

Explanation:

Let's consider the following balanced equation.

3 Fe₂O₃(s) + H₂(g) ⇒ 2 Fe₃O₄(s) + H₂O(g)

When 1 mole of Fe₂O₃(s) reacts, 2.00 kJ of energy are evolved. Energy is an extensive property. In the balanced equation there are 3 moles of Fe₂O₃(s), so the evolved energy is:

$3molFe_{2}O_{3}.\frac{2.00kJ}{1molFe_{2}O_{3}} =6.00kJ$

By convention, when energy is evolved it takes the negative sign. At constant pressure, the thermochemical equation is:

3 Fe₂O₃(s) + H₂(g) ⇒ 2 Fe₃O₄(s) + H₂O(g)    ΔH° = -6.00 kJ

where

ΔH° is the standard enthalpy of reaction (heat released at constant pressure)