Multiple Choice
Calculate ΔrH for the reaction: CH4(g) + 4 Cl2(g) → CCl4(g) + 4 HCl(g) using the given ΔfH values: CH4(g) ΔfH = -74.6 kJ/mol, CCl4(g) ΔfH = -95.7 kJ/mol, and HCl(g) ΔfH = -92.3 kJ/mol.
8. Thermochemistry
Thermochemical Equations
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How much heat is absorbed when 30.00 g of C(s) reacts in the presence of excess SO2(g) to produce CS2(l) and CO(g) according to the following chemical equation? 5 C(s) + 2 SO2(g) → CS2(l) + 4 CO(g), ΔH = 239.9 kJ
A
119.95 kJ
B
143.9 kJ
C
47.98 kJ
D
239.9 kJ
Verified step by step guidance1
Identify the given chemical reaction: 5 C(s) + 2 SO2(g) → CS2(l) + 4 CO(g) with ΔH = 239.9 kJ. This means that 239.9 kJ of heat is absorbed when 5 moles of carbon react.
Determine the molar mass of carbon (C), which is approximately 12.01 g/mol.
Calculate the number of moles of carbon in 30.00 g using the formula: \( \text{moles of C} = \frac{\text{mass of C}}{\text{molar mass of C}} \).
Use the stoichiometry of the reaction to find the heat absorbed for the moles of carbon calculated. Since 5 moles of C absorb 239.9 kJ, set up a proportion to find the heat absorbed by the moles of C you calculated: \( \frac{239.9 \text{ kJ}}{5 \text{ moles of C}} = \frac{x \text{ kJ}}{\text{moles of C calculated}} \).
Solve the proportion to find the value of x, which represents the heat absorbed when 30.00 g of C reacts.
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