Chemistry - Thermochemistry Question with Solution | TestHub
ChemistryThermochemistryEnthalpy of solution/dilution/hydrationHard2 minQB
ChemistryHardsingle choice
Passage / Comprehension
The thermal effects of reactions in liquid NH3 at -33°C were measured by observing the quantity of liquid NH3 vaporized by the process of interest. The heat of vaporization of NH3 at -33°C is 320.0 cal/g. When 1.07 g of NH4Cl was dissolved in 25 g of liquid NH3, 0.75 g of NH3 was vaporized. (Cl = 35.5)
When 0.535 g NH4Cl was dissolved in 25 g of liquid NH3 containing an equimolar amount of KNH2, 1.20 g of ammonia was vaporized. The ΔH for the reaction:
NH4+(NH3, l) + NH2-(NH3, l) → 2NH3(l)
at 240 K is
Options:
Answer:
D
Solution:
0.535 g NH4Cl = 0.535/53.5 = 0.0100 mol, so NH4+ and NH2- are each 0.0100 mol. Heat taken by vaporizing 1.20 g NH3 = 1.20 × 320 = 384 cal, released by the reaction. Per mole of reaction: -384/0.0100 = -38,400 cal = -38.4 kcal. Ans (d).
Stream:JEESubject:ChemistryTopic:ThermochemistrySubtopic:Enthalpy of solution/dilution/hydration
⏱ 2mℹ️ Source: QB
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