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Question

Chemistry Question on Thermodynamics

Which of following lines correctly show the temperature dependence of equilibrium constant KK, for an exothermic reaction ?

A

A and B

B

B and C

C

C and D

D

A and D

Answer

A and B

Explanation

Solution

Equilibrium constant K=(AfAb)eΔHRTK =\left(\frac{ A _{ f }}{ A _{ b }}\right) e ^{-\frac{\Delta H ^{\circ}}{ RT }} ln K=K = ln (AfAb)ΔHR(1T)\left(\frac{ A _{ f }}{ A _{ b }}\right)-\frac{\Delta H ^{\circ}}{ R }\left(\frac{1}{ T }\right) y=C+mxy = C + m x Comparing with equation of straight line, Slope =ΔHR=\frac{-\Delta H^{\circ}}{R} Since, reaction is exothermic, ΔH=ve\Delta H ^{\circ}=- ve, therefore, slope =+ve= +ve