Question

Hydrazine (N2H4) is used as a rocket fuel. The combustion products are nitrogen (N2) and water (H2O). Use the following information about bond energies to estimate the change in enthalpy associated with the combustion of 1 mol of hydrazine
Bond Bond Energy (kJ/mol)

N–N 163

N=N 418

N N 941 <- triple bond

N–H 388

O–O 146

O=O 495

O–H 463

a. −583 kJ/mol d. −358 kJ/mol b. +2,450 kJ/mol e. −1,970 kJ/mol c. −1,078 kJ/mol

Answer 1

Answer:

a. −583 kJ/mol

Explanation:

First we start with the balanced chemical equation

N2H4 + O2 ------> N2 + 2 H2O

Breaking bonds is endothermic, it requires energy whereas bond forming is exothermic, it expels energy. So the net energy change during this reaction can be calculated this way

ΔH = bond breaking energy - bond forming energy

     = (4*388+163 + 495) - (941+4*463)

    = -583 kJ/mol