<p>The standard enthalpy of formation of&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi><msub><mi>H</mi><mn>3</mn></msub></math>&nbsp;is -46.0 kJ&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>. If the enthalpy of formation of&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>H</mi><mn>2</mn></msub></math>&nbsp;from its atoms is -436 kJ&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>&nbsp;and that of&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>N</mi><mn>2</mn></msub></math>&nbsp;is -712 kJ&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>, the average bond enthalpy of N-H bond in&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi><msub><mi>H</mi><mn>3</mn></msub></math>&nbsp;is:</p>