NEET2025Chemistry-Thermochemistry
NEET 2025 Chemistry Heat of Formation MCQ Question
Type: MCQ-numerical-Hard-Class 11
The standard heat of formation, in kcal/mol of Ba²⁺ is: [Given: standard heat of formation of SO₄²⁻ 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]
A
-128.5
B
-133.0
C
+133.0
D
+220.5
Correct Answer
Option A
Detailed Explanation
Using the equation: ΔHf(Ba²⁺) = ΔHf(BaSO₄) - ΔHf(SO₄²⁻) - ΔHcryst(BaSO₄), we find ΔHf(Ba²⁺) = -³⁴⁹⁻ (-216) - (-4.5) = -133.0 kcal/mol.
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