Q.22. Calculate the entropy change in surroundings when 1.00 mol of H2Ol is formed under standard conditions. fHθ=-286kJmol-1.

NEETprep Answer:
The positive value of ∆rH indicates that heat is absorbed during the formation of NO(g).
This means that NO(g) has higher energy than the reactants (N2andO2). Hence, NO(g) is unstable.
The negative value of ∆rH indicates that heat is evolved during the formation of NO2(g) from
NO(g) and O2(g). The product, NO2g is stabilized with minimum energy.
Hence, unstable NO(g) changes to unstable NO2g.