Q. 83.7( 59 Votes )

The reaction of cyanamide, NH2CN (s), with dioxygen was carried out in a bomb calorimeter, and DU was found to be –742.7 kJ mol–1 at 298 K. Calculate enthalpy change for the reaction at 298 K.


Answer :

We know that,

ΔU = ΔH - ΔngRT


The balanced chemical equation of reaction is,


NH2CN(s) + 3/2O2(g) N2(g) + CO2(g) + H2O(l)


Number of moles of gaseous particles in product side is 2 (one N2 and one CO2)


Number of moles of gaseous particles on reactant side is 3/2 (O2)


Thus, change in number of moles of gaseous particle,


Δng = 2 – 3/2 = 1/2


ΔU = ΔH - ΔngRT

Given,

ΔU = -742.7 kJ

R =8.314 J K-1 mol-1

= 8.414 × 10-3 kJ K-1 mol-1

Δng =(2-2.5) =-0.5 mole

T = 298 K

Thus,

ΔH = (-742.7 kJ mol-1) – (1/2mol)×(8.314 × 10-3 kJ K-1mol-1)×298

= -742.7 - 1.239

= -743.9 kJ

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Calorimetry - 02 | Mastering important conceptsCalorimetry - 02 | Mastering important conceptsCalorimetry - 02 | Mastering important concepts39 mins
Thermal Properties of Matter | Matering important conceptsThermal Properties of Matter | Matering important conceptsThermal Properties of Matter | Matering important concepts48 mins
Hess LawHess LawHess Law61 mins
Thermodynamics | Types of EnthalpyThermodynamics | Types of EnthalpyThermodynamics | Types of Enthalpy66 mins
Enthalpy & Heat Capacity | Interactive QuizEnthalpy & Heat Capacity | Interactive QuizEnthalpy & Heat Capacity | Interactive Quiz55 mins
An interesting lecture on EntropyAn interesting lecture on EntropyAn interesting lecture on Entropy63 mins
Heat Transfer - 01 | Mastering important conceptsHeat Transfer - 01 | Mastering important conceptsHeat Transfer - 01 | Mastering important concepts40 mins
Entropy | Rapid QuizEntropy | Rapid QuizEntropy | Rapid Quiz45 mins
Heat Transfer -02 | Mastering important conceptsHeat Transfer -02 | Mastering important conceptsHeat Transfer -02 | Mastering important concepts49 mins
Enthalpy of combustion | Mastering important conceptsEnthalpy of combustion | Mastering important conceptsEnthalpy of combustion | Mastering important concepts44 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
caricature
view all courses