Use Hess's Law to Calculate the Enthalpy Change for the Reaction

question 67

Multiple Choice

Use Hess's Law to calculate the enthalpy change for the reaction $$\mathrm{WO}_{3}(s) +3 \mathrm{H}_{2}(g) \rightarrow W(s) +3 \mathrm{H}_{2} \mathrm{O}(g)$$
from the following data:
$$\begin{array}{l}2 \mathrm{~W}(\mathrm{~s}) +3 \mathrm{O}_{2}(g) \rightarrow 2 \mathrm{WO}_{3}(\mathrm{~s}) , \Delta \mathrm{H}=-1685.4 \mathrm{~kJ} \\2 \mathrm{H}_{2}(g) +\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(g) , \Delta H=-477.84 \mathrm{~kJ}\end{array}$$

• A) 125.9 kJ
• B) 252.9 kJ
• C) 364.9 kJ
• D) 1207.6 kJ
• E) None of these choices is correct.

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