Question

For a reversible reaction : `X_((g))+3Y_((g))iff2Z_((g)), DeltaH=-40kJ` the standard entropies of X, Y and Z are 60, 40 and 50 `JK^(-1) mol^(-1)` respectively. The temperature at which the above reaction attains equilibrium is about
A. 400 K
B. 500 K
C. 273 K
D. 373 K

Answer 1

Correct Answer - B
`X_((g))+3Y_((g))iff2Z_((g))`
`DeltaS^(@)=2S^(@)(Z)-{S^(@)(X)+3S^(@)(Y)}`
`=2xx50-{60+3xx40}=100-180 " = - 80 J K"^(-1) mol^(-1)`
`DeltaH^(@)=-40 kJ=-40,000 J," " DeltaG^(@)=DeltaH^(@)-TDeltaS^(@)`
At equilibrium, `DeltaG^(@)=0 " "therefore DeltaH^(@)=TDeltaS^(@)`
`or, T = (DeltaH^(@))/(DeltaS^(@))=(40000)/(80)=500 K`.