The standard heat of formation, in kcal / mol ^ of Ba ^ 2+ is : [Given : standard heat of formation of SO _4^ 2- ion (aq) =-216 kcal / mol , Standard heat of crystallisation of BaSO _4( ~s )=-4.5 kcal / mol , standard heat of formation of . BaSO _4( ~s )=-349 kcal / mol ]

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Quantrex Academy · Accepted Answer

Correct answer: A. -128.5

aligned & H _ crys ( BaSO _4 )= H _ f ( BaSO _4 )- [ H _ f ( Ba ^ +2 )+ H _ f ( SO _4^ -2 ) ] \ & -4.5=[-349]- [ H _ f ( Ba ^ +2 )+(-216) ] \ & H _ f ( Ba ^ +2 )=-128.5 kCal ~mol ^ -1 aligned

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