Q. 13. Given

N2g+3H2g2NH3g;rHθ=-92.4kJmol-1

What is the standard enthalpy of formation of NH3 gas?

NEETprep Answer:
Standard enthalpy of formation of a compound is the change in enthalpy that takes place during the formation of 1 mole of a substance in its standard form from its constituent elements in their standard state.
Re-writing the given equation for 1 mole of NH3g,
12N2g+32H2gNH3g
Standard enthalpy of formation of NH3g
=12rHθ
=12-92.4kJmol-1
=-46.2kJmol-1