Question

Using the information given below, calculate ΔHrxn for WO₃(s) + 3H₂(g) => W(s) + 3H₂O(g) 2W(s) + 3O₂(g) => 2WO₃(s) ΔH = -1685 kJ 2H₂(g) + O₂(g) => 2H₂O(g) ΔH = -477.84 kJ

A. -252.9 kJ
B. 252.9 kJ
C. 125.9 kJ
D. 364.9 kJ
E. 1207.6 kJ

Answer 1

To calculate ΔHrxn for the given reaction, we can use Hess's Law and the given enthalpy changes. By manipulating the given equations and combining them, we can obtain the desired reaction and calculate ΔHrxn.

Step-by-step explanation:

To calculate ΔHrxn for the given reaction, we can use Hess's Law and the given enthalpy changes:

1. Multiply the first equation by 2 so that the number of WO₃ on the left side matches the desired reaction:
2W(s) + 3O₂(g) → 2WO₃(s) ΔH = -1685 kJ x 2 = -3370 kJ

2. Reverse the second equation to match the desired reaction:
2H₂O(g) → 4H₂(g) + 2O₂(g) ΔH = -477.84 kJ

3. Combine the two equations to obtain the desired reaction:
WO₃(s) + 3H₂(g) → W(s) + 3H₂O(g) ΔH = -3370 kJ + (-477.84 kJ) = -3847.84 kJ