Question

What is the equilibrium constant, K for the following reaction at 400 K?
`2NOCl (g) hArr 2NO(g)+Cl_(2)(g)`
`DeltaH=77.2" kJ "mol^(-1) and DeltaS=122JK^(-1)mol^(-1)` at 400K.
A. `-3.708`
B. `1.95xx10^(-4)`
C. `2.8xx10^(4)`
D. `1.67xx10^(-5)`

Answer 1

Correct Answer - B
`DeltaG=DeltaH-TDeltaS`
`=77.2-400xx122xx10^(-3)`
`=+28.4kJ" "mol^(-1)=28400" J "mol^(-1)`
Further, `DeltaG=-2.303RTlogK`
or `28400=-2.303xx8.314xx400xxlogK`
`logK=-(28400)/(2.303xx8.314xx400)`
`logK=-3.708`
`K=`Antilog (-3.708)`=1.95xx10^(-4)`