객관식
Calculate the ∆Hrxn for the following thermochemical equation:
S (s) + O2 (g) → SO3 (s) ΔHrxn = ?
When given the following:
2 S (s) + 3 O2 (g) → 2 SO3 (s) ΔHrxn = −296.8 kJ
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7. Energy, Rate and Equilibrium
Hess's Law
Multiple Choice
Calculate the ∆Hrxn for
Given the following set of reactions:
A
-494.4 kJ
B
-692.8 kJ
C
494.4 kJ
D
-346.4 kJ
검증된 단계별 안내1
Identify the target reaction: S (s) + \(\frac{3}{2}\) O_2 (g) \(\rightarrow\) SO_3 (g). We need to find the \(\Delta\) H_{rxn} for this reaction.
Examine the given reactions and their enthalpy changes: \(\frac{1}{2}\) S (s) + \(\frac{1}{2}\) O_2 (g) \(\rightarrow\) \(\frac{1}{2}\) SO_2 (g) with \(\Delta\) H^\(\circ\) = -296.8 \(\text{ kJ}\), and 2 SO_3 (g) \(\rightarrow\) 2 SO_2 (g) + O_2 (g) with \(\Delta\) H^\(\circ\) = 198.4 \(\text{ kJ}\).
Use Hess's Law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for each step. We need to manipulate the given reactions to match the target reaction.
Reverse the second reaction to get: 2 SO_2 (g) + O_2 (g) \(\rightarrow\) 2 SO_3 (g). This changes the sign of \(\Delta\) H^\(\circ\) to -198.4 \(\text{ kJ}\).
Add the modified reactions: \(\frac{1}{2}\) S (s) + \(\frac{1}{2}\) O_2 (g) \(\rightarrow\) \(\frac{1}{2}\) SO_2 (g) and 2 SO_2 (g) + O_2 (g) \(\rightarrow\) 2 SO_3 (g). Adjust stoichiometry and sum the enthalpy changes to find \(\Delta\) H_{rxn} for the target reaction.
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