The standard heat of formation in kcal/mol of is Given: standard heat of formation of = kcal/mol, standard heat of crystallisation of kcal/mol, standard heat of formation of kcal/mol. [2025]

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Solution

Q.
The standard heat of formation in kcal/mol of ${Ba}^{2 +}$ is

Given: standard heat of formation of ${SO}_{4}^{2 -}$ $i o n_{(a q)}$ = $- 216$ kcal/mol, standard heat of crystallisation of $B a S {O_{4}}_{(s)} = - 4.5$ kcal/mol, standard heat of formation of $B a S {O_{4}}_{(s)} = - 349$ kcal/mol. [2025]

1 +133.0

2 +220.5

3 -128.5

4 -133.0

Ans.
(3)

$Δ H_{f} ({BaSO}_{4}) = Δ H_{f} ({Ba}^{2 +}) + Δ H_{f} ({SO}_{4}^{2 -}) + Δ H_{crys.} ({BaSO}_{4})$

$Δ H_{f} ({Ba}^{2 +}) = Δ H_{f} ({BaSO}_{4}) - Δ H_{f} ({SO}_{4}^{2 -}) - Δ H_{crys.} ({BaSO}_{4})$

$Δ H_{f} ({Ba}^{2 +}) = - 349 + 216 + 4.5 kcal/mol$

$= - 128.5$ $kcal/mol$

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