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

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

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

Explanation: