标准状态下，气态分子断开l $mol$化学键的焓变称为键焓。已知$H-H$、$H-O$和$O-O$键的键焓$\Delta H$分别为436 $kJ/mol$、463 $kJ/mol$和495$kJ/mol$。下列热化学方程式正确的是

$H_{2}O\left(g\right)= H_2\left(g\right)+O_2\left(g\right); \Delta H=-485 kJ/mol$

$H_{2}O\left(g\right)=H_2\left(g\right)+O_2\left(g\right); \Delta H=+485 kJ/mol$

$2H_2\left(g\right)+O_{2 }\left(g\right)=2H_{2}O\left(g\right) \Delta H =+485 kJ/mol$

$2H_2(g0+O_2(g)=2H_{2}O(g) \Delta H = -485 kJ/mol$