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Chemistry · PYQ NEET UG 2025
हिन्दीThe standard heat of formation, in \( \text{kcal/mol} \) of \( \text{Ba}^{2+} \) is : [Given : standard heat of formation of \( \text{SO}_4^{2-} \text{ (aq)} = -216 \text{ kcal/mol} \), standard heat of crystallisation of \( \text{BaSO}_4\text{(s)} = -4.5 \text{ kcal/mol} \), standard heat of formation of \( \text{BaSO}_4\text{(s)} = -349 \text{ kcal/mol} \)]
Correct answer · Option 1
- 128.5
Explanation
Applying Hess's law, \( \Delta H_f(\text{Ba}^{2+}) = \Delta H_f(\text{BaSO}_4) - \Delta H_f(\text{SO}_4^{2-}) - \Delta H_{\text{cryst}}(\text{BaSO}_4) = -349 - (-216) - (-4.5) = -128.5 \text{ kcal/mol} \).
