The standard enthalpy of formation of gaseous H2 O at 298 K is -241.82 kJ / mol . Calculate ΔH

step 1 Hello students in this question we have to calculate we have to calculate the delta h0 for the r

The standard enthalpy of formation of gaseous H2 O at 298 K...

The standard enthalpy of formation of gaseous $\mathrm{H}_{2} \mathrm{O}$ at $298 \mathrm{~K}$ is $-241.82 \mathrm{~kJ} / \mathrm{mol} .$ Calculate $\Delta H^{\circ}$ at $373 \mathrm{~K}$ given the following values of the molar heat capacities at constant pressure : $\mathrm{H}_{2} \mathrm{O}(g)=33.58 \mathrm{JK}^{-1} \mathrm{~mol}^{-1} ; \mathrm{H}_{2}(g)=29.84 \mathrm{JK}^{-1} \mathrm{~mol}^{-1} ; \mathrm{O}_{2}(g)=29.37 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$ Assume that the heat capacities are independent of temperature : (a) $-242.6 \mathrm{~kJ} / \mathrm{mol}$ (b) $-485.2 \mathrm{~kJ} / \mathrm{mol}$ (c) $-121.3 \mathrm{~kJ} / \mathrm{mol}$ (d) $-286.4 \mathrm{~kJ} / \mathrm{mol}$

The standard enthalpy of formation of gaseous $\mathrm{H}_{2} \mathrm{O}$ at $298 \mathrm{~K}$ is $-241.82 \mathrm{~kJ} / \mathrm{mol} .$ Calculate $\Delta H^{\circ}$ at $373 \mathrm{~K}$ given the following values of the molar heat capacities at constant pressure :
$\mathrm{H}_{2} \mathrm{O}(g)=33.58 \mathrm{JK}^{-1} \mathrm{~mol}^{-1} ; \mathrm{H}_{2}(g)=29.84 \mathrm{JK}^{-1} \mathrm{~mol}^{-1} ; \mathrm{O}_{2}(g)=29.37 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$
Assume that the heat capacities are independent of temperature :
(a) $-242.6 \mathrm{~kJ} / \mathrm{mol}$
(b) $-485.2 \mathrm{~kJ} / \mathrm{mol}$
(c) $-121.3 \mathrm{~kJ} / \mathrm{mol}$
(d) $-286.4 \mathrm{~kJ} / \mathrm{mol}$

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Key Concepts

Standard Enthalpy of Formation

This is the enthalpy change when one mole of a compound is formed from its elements in their standard states. It serves as a reference for calculating reaction energies and helps in understanding how much energy is absorbed or released during compound formation.

Heat Capacity at Constant Pressure

This thermodynamic property characterizes the amount of energy needed to raise the temperature of a substance at constant pressure. It is crucial for calculating how the enthalpy of a system changes with temperature, as it determines the energy required to heat or cool the system.

Kirchhoff's Law

Kirchhoff's Law relates the temperature dependence of the reaction enthalpy to the difference in heat capacities between the products and reactants. It allows the adjustment of enthalpy changes from one temperature to another by integrating the difference in heat capacities over the temperature interval.

Temperature Dependence of Enthalpy

This concept highlights that enthalpy is not a constant value but varies with temperature. By considering the heat capacities of the reactants and products, one can calculate how the enthalpy change for a reaction shifts when the system is heated or cooled to different temperatures.

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