H2+(1)/(2) O2 ⟶H2 O ; Δ/ I=-68.39 kcal K+aq ⟶KOH(aq)+(1)/(2) H2( g) ; Δ/ /=-48 kca 1 KOH+aq ⟶KOH

step 1 Hydrogen gas plus half molecule of oxygen forms water. Heat of entropy is minus 68 .39 kilo cal.

H2+(1)/(2) O2 ⟶H2 O ; Δ/ I=-68.39 kcal K+aq ⟶KOH(aq)+(1)/(2)...

$\mathrm{H}_{2}+\frac{1}{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{O} ; \Delta / I=-68.39 \mathrm{kcal}$ $\mathrm{K}+\mathrm{aq} \longrightarrow \mathrm{KOH}(\mathrm{aq})+\frac{1}{2} \mathrm{H}_{2}(\mathrm{~g}) ; \Delta / /=-48 \mathrm{kca} 1$ $\mathrm{KOH}+\mathrm{aq} \longrightarrow \mathrm{KOH}(\mathrm{aq}) ; \Delta H=14 \mathrm{kcal}$ The heat of formation (in $\mathrm{kcal}$ ) of KOII is (1) $-68.3948-14$ (2) $-68.39-48+14$ (3) $68.39-48+14$ (4) $68.39+48+14$

$\mathrm{H}_{2}+\frac{1}{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{O} ; \Delta / I=-68.39 \mathrm{kcal}$
$\mathrm{K}+\mathrm{aq} \longrightarrow \mathrm{KOH}(\mathrm{aq})+\frac{1}{2} \mathrm{H}_{2}(\mathrm{~g}) ; \Delta / /=-48 \mathrm{kca} 1$
$\mathrm{KOH}+\mathrm{aq} \longrightarrow \mathrm{KOH}(\mathrm{aq}) ; \Delta H=14 \mathrm{kcal}$
The heat of formation (in $\mathrm{kcal}$ ) of KOII is
(1) $-68.3948-14$
(2) $-68.39-48+14$
(3) $68.39-48+14$
(4) $68.39+48+14$

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Key Concepts

Thermochemical Equations

Thermochemical equations are balanced chemical equations that include the enthalpy change associated with the reaction. They allow for systematic energy accounting in chemical processes by combining known reactions to construct the target reaction.

Reaction Enthalpy Calculations

Reaction enthalpy calculations involve combining the heats of formation or reaction steps, often using Hess's Law, to determine the overall energy change of a reaction. This method is essential for predicting whether a reaction is exothermic or endothermic and for designing energy-efficient chemical processes.

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same regardless of the number of steps or the pathway taken. It allows us to calculate the reaction enthalpy by summing the enthalpy changes of individual, often simpler, reactions that add up to the overall process.

Standard Enthalpy of Formation

The standard enthalpy of formation is the heat change that accompanies the formation of one mole of a compound from its elements in their standard states. This concept is fundamental for determining the energy changes in chemical reactions, and it serves as a baseline for comparing reactions.

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