At 300 K , the standard enthalpies of formation of C6 H5 COOH(s), CO, (g) and H2 O(s) are -408,-

step 1 We are given that the benjoic acid which is C6H5 C O .O .H in solid state plus 15 by 2 o2 which

At 300 K , the standard enthalpies of formation of C6 H5...

At 300 K , the standard enthalpies of formation of $\mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}(\mathrm{s}), \mathrm{CO}$, (g) and $\mathrm{H}_2 \mathrm{O}(\mathrm{s})$ are $-408,-393$ and $-286 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. Calculate the heat of combustion of benzoic acid at constant volume. (a) $-3296 \mathrm{~kJ} \mathrm{~mol}^{-1}$ (b) $-3200 \mathrm{~kJ} \mathrm{~mol}^{-1}$ (c) $-3201 \mathrm{~kJ} \mathrm{~mol}^{-1}$ (d) $-3603 \mathrm{~kJ} \mathrm{~mol}^{-1}$

At 300 K , the standard enthalpies of formation of $\mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}(\mathrm{s}), \mathrm{CO}$, (g) and $\mathrm{H}_2 \mathrm{O}(\mathrm{s})$ are $-408,-393$ and $-286 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. Calculate the heat of combustion of benzoic acid at constant volume.
(a) $-3296 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(b) $-3200 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(c) $-3201 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(d) $-3603 \mathrm{~kJ} \mathrm{~mol}^{-1}$

Key Concepts

Constant Volume Conditions

Constant volume conditions refer to a scenario where the volume remains fixed during a reaction, such as in a bomb calorimeter. Under these conditions, the measured energy change corresponds to the change in internal energy (?U) rather than the enthalpy change (?H) observed at constant pressure, which is important in accurately assessing the energy released during a reaction.

Enthalpy of Formation

Enthalpy of formation is the heat change that results when one mole of a compound is formed from its elements in their standard states. This concept is crucial for calculating reaction enthalpies using Hess’ law, as it provides the necessary baseline energies of compounds and elements involved in chemical reactions.

Heat of Combustion

The heat of combustion is the energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions. It is a key concept in thermochemistry because it quantifies the energy content of fuels and other substances when oxidized, and it can be determined using the enthalpies of formation of reactants and products.

Hess’ Law

Hess’ law states that the total enthalpy change of a chemical reaction is the same irrespective of the reaction pathway, because enthalpy is a state function. This allows for the calculation of difficult-to-measure enthalpy changes, such as heat of combustion, by summing the known enthalpy changes of formation for the products and reactants.

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