当1g氨气完全分解为氮气、氢气时,吸收2.72kJ的热量,则下列热化学方程式正确的是①N2(g)+3H2(g)===2NH3(g) ΔH=-92.4kJ/mol②N2(g)+3H2(g)===2NH3(g) ΔH=-46.2kJ/mol③NH3(g)===1/2N2(g)+3/2H2(g) ΔH=+46.2kJ/mol④2NH3(g)===N2(g)+3H2(g) ΔH=-92.4kJ/mol