Question

Based on the following equation what is the heat of formation, ΔHf°, for H2O(l) 

2H2(g)+O2(g)=2H2O(l)+136.6kcal

Answer 1

Gives

$$2H_2(g)+o_2\rightarrow2H_2o(l)+136.6kcal$$

$$∆H_fr=H_r-H_p=136.6\times4.2kJ/mol$$

$$∆H_{fr}=2\times0+2\times0-2\times(-285.8)$$

∆H_fr=571.6kJ/mol

$$∆H_{fr}=571.6kJ/mol\times2mol=1143.2kJ$$

$$∆H_{f}=1143.2KJ-573.72KJ=569.48KJ$$