Electric generating plants transport large amounts of hot water through metal pipes, and oxygen dissolved in the water can
cause a major corrosion problem. Hydrazine (N2H4) added to the
water prevents this problem by reacting with the oxygen:

N2H4(aq) + O2(g) ⟶ N2(g) + 2H2O(l)

About 4×107 kg of hydrazine is produced every year by reacting
ammonia with sodium hypochlorite in the Raschig process:

2NH3(aq) + NaOCl(aq) ⟶ N2H4(aq) + NaCl(aq) + H2O(l)

ΔHrxn ° = −151 kJ

(a) If ΔH°f of NaOCl(aq) = −346 kJ/mol, find ΔHf° of N2H4(aq).

(b) What is the heat released when aqueous N2H4 is added to
5.00×103L of water that is 2.50×10−4 M O2?