Question

The energy change
H associated with the
reaction
NBr3(g) + 3H2O(g) -> 3HOBr(g) + NH3(g)
is +81 kJ/mol rxn.
These bond energy values might be useful:
O-H 459 kJ/mol; N-H 386 kJ/mol; O-Br 201
kJ/mol.
The strength of the N Br bond is
1. 4 kJ/mol
2. 465 kJ/mol
3. 66 kJ/mol
4. 128 kJ/mol
5. 248 kJ/mol
6. 280 kJ/mol
7. 155 kJ/mol

Answer 1

delta Hrxn = (sum bonds broken reactants) - (sum bonds formed products).
Solve for NBr bonds and divide by 3.

Answer 2

66 kJ/mol