From the following data, the heat of formation of Ca(OII)2( s) at 18^∘ C is …. . kcal . Δ/ l18 ^

step 1 From the following data, the heat of formation of calcium hydroxide in solid state at 18 degrees

From the following data, the heat of formation of...

From the following data, the heat of formation of $\mathrm{Ca}(\mathrm{OII})_{2}(\mathrm{~s})$ at $18^{\circ} \mathrm{C}$ is $\ldots . . \mathrm{kcal} .$ $\Delta / l_{18{ }^{\circ} \mathrm{c}}=-15.26 \mathrm{kcal}$ $\mathrm{II}_{2} \mathrm{O}(\mathrm{l})+\mathrm{II}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) ; \Delta H_{18 \mathrm{C}}=68.37 \mathrm{kcal}$ $\mathrm{Ca}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \stackrel{2}{\longrightarrow} \mathrm{CaO}(\mathrm{s}) ; \Delta / I_{18^{\circ} \mathrm{C}}=-151.8 \mathrm{keal}$ (1) $-98.69$ (2) $-235.43$ (3) $194.91$ (4) $98.69$

From the following data, the heat of formation of $\mathrm{Ca}(\mathrm{OII})_{2}(\mathrm{~s})$ at $18^{\circ} \mathrm{C}$ is $\ldots . . \mathrm{kcal} .$
$\Delta / l_{18{ }^{\circ} \mathrm{c}}=-15.26 \mathrm{kcal}$
$\mathrm{II}_{2} \mathrm{O}(\mathrm{l})+\mathrm{II}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) ; \Delta H_{18 \mathrm{C}}=68.37 \mathrm{kcal}$
$\mathrm{Ca}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \stackrel{2}{\longrightarrow} \mathrm{CaO}(\mathrm{s}) ; \Delta / I_{18^{\circ} \mathrm{C}}=-151.8 \mathrm{keal}$
(1) $-98.69$
(2) $-235.43$
(3) $194.91$
(4) $98.69$

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Key Concepts

Enthalpy of Formation

Enthalpy of formation is the change in enthalpy when one mole of a compound is formed from its constituent elements in their standard states. It is a fundamental concept in thermochemistry that allows the estimation of reaction energetics, providing insight into the energy required to create a compound from its elements under standard conditions.

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 from reactants to products. This principle is critical because it allows the calculation of unknown enthalpy changes by algebraically combining other reactions with known enthalpy changes.

Thermochemical Equations

Thermochemical equations represent chemical reactions with their associated enthalpy changes. They are used to track the energy flow in chemical processes, showing how the enthalpy changes of individual reaction steps combine to yield the overall reaction enthalpy. This concept is essential for applying Hess's Law and understanding the energetic aspects of reactions.

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