The correct option is B -2.7 kcal
ΔH=ΔU+ΔngRT
Given, ΔU=2.1 kcal, Δng=2
R=2×10−3kcal, T=300K
∴ ΔH=2.1+2×2×10−3×300=3.3 kcal
Again, ΔG=ΔH−TΔS
Given, ΔS=20×10−3kcal K−1
On putting the values of ΔH and ΔS in the equation, we get
ΔG=3.3−300×20×10−3
=3.3−6×103×10−3=2.7 kcal