Consider the following reactions i H + aq + OH − aq → H 2 O l , ΔH = − X 1 kJmol − 1 ii H 2 g + 1 / 2 O 2 g → H 2 O l , ΔH = − X 2 kJmol − 1 iii CO 2 g + H 2 g → CO g + H 2 O l , ΔH = − X 3 kJmol − 1

Question

Consider the following reactions i H + aq + OH − aq → H 2 O l , ΔH = − X 1 kJmol − 1 ii H 2 g + 1 / 2 O 2 g → H 2 O l , ΔH = − X 2 kJmol − 1 iii CO 2 g + H 2 g → CO g + H 2 O l , ΔH = − X 3 kJmol − 1 iv C 2 H 2 g + 5 / 2 O 2 g → 2 CO 2 g + H 2 O l , ΔH = + X 4 kJmol − 1 Enthalpy of formation of H 2 O l is

TestHub · Accepted Answer

The amount of heat absorbed or released when 1 mole of a substance is directly obtained from its constituent element is called the heat of formation of enthalpy of formation.
Equation (i) represents neutralisation reaction, (iii) represents hydrogenation reaction and (iv) represents combustion reaction.

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