The standard heat of formation, in kcal/mol of Ba 2+ is : [Given : standard heat of formation of SO4 2- ion (aq) = -216 kcal/mol, standard heat of crystallisation of BaSO4(s) = -4.5 kcal/mol, standard heat of formation of BaSO4(s) = -349 kcal/mol]

1. A. + 220.5
2. B. - 128.5
3. C. - 133.0
4. D. + 133.0

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