Chemistry · Thermochemistry

To find the heat of combustion of carbon monoxide (CO), we can apply Hess's Law. The heat of formation of CO is -26.4 Kcal, and the heat of formation of CO₂ is -94.0 Kcal. The combustion of CO can be represented as:

2 CO + O₂ → 2 CO₂.

To find the heat of combustion, we can use the equation:

ΔH_comb = ΣΔH_f (products) - ΣΔH_f (reactants).

Calculating this gives:

ΔH_comb = [2(-94.0 Kcal)] - [2(-26.4 Kcal)] = -188.0 Kcal + 52.8 Kcal = -135.2 Kcal for two moles of CO. Dividing by 2 to find the heat for one mole gives -67.6 Kcal. Therefore, the correct answer is -67.6 Kcal. The other options are incorrect because they either misinterpret the direction of energy transfer or do not accurately apply Hess's Law.

This option incorrectly suggests that the heat of combustion is positive, which implies that energy is absorbed rather than released during combustion. Combustion reactions are typically exothermic.

This is the correct answer. It represents the heat of combustion of carbon monoxide, calculated by applying Hess's Law using the heats of formation of CO and CO2.

This option also suggests a positive value for the heat of combustion, which is incorrect since combustion releases energy. It is not consistent with typical combustion thermodynamics.

This value does not correspond to the correct calculation based on Hess's Law. It suggests an incorrect interpretation of the heat of combustion and heat of formation values.