Chemistry - Thermochemistry Question with Solution | TestHub
ChemistryThermochemistryHess's Law of Constant Heat SummationEasy2 minQB
ChemistryEasysingle choice
A chemist studying nickel compounds considers the reactions:
Ni(OH)2 + 2HCl → NiCl2 + 2H2O; ΔH = -25 kcal
Ni(OH)2 + 2HBr → NiBr2 + 2H2O; ΔH = -30 kcal
In an experiment, 0.25 kcal was absorbed when one mole of NiBr2 was mixed with 2 moles of HCl. What is the percentage conversion of NiBr2 into NiCl2?
Options:
Answer:
D
Solution:
Subtracting the second equation from the first yields:
NiBr2 + 2HCl → NiCl2 + 2HBr
The change in enthalpy for this reaction is ΔH = -25 - (-30) = +5 kcal/mol.
A full conversion of 1 mol would absorb 5 kcal. The observed absorption is 0.25 kcal.
Therefore, the percentage of conversion is calculated as:
Conversion = 0.25 kcal/5 kcal/mol = 0.05 = 5%
This corresponds to option (d).
Stream:JEESubject:ChemistryTopic:ThermochemistrySubtopic:Hess's Law of Constant Heat Summation
⏱ 2mℹ️ Source: QB
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