<p>The enthalpy of formation of ammonia gas at 298 K is -46.11 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 equation to which this value relates is:</p>