Chemical thermodynamics

Enthalpy of formation

Exercise 6

     

Calculate the standard enthalpy variation of the reaction of combustion of ammonia (producing nitrogen monoxyde and water) by consulting the →   Table of formation enthalpies :

$4NH_3$ $+$ $5O_2$ $\longrightarrow$ $4NO$ $+$ $6H_2O(l)$

Combustion reaction (combustion of one mole) of ammonia: $NH_3$ $+$ $\frac{5}{4}O_2$ $\longrightarrow$ $NO$ $+$ $\frac{3}{2}H_2O(l)$

$\Delta H_c(NH_3)$ $=$ $(\Delta H_f(NO(g))$ $+$ $\frac{3}{2}\Delta H_f(H_2O(l)))$ $-$ $\Delta H_f(NH_3(g)$ $=$ $-292.385 \;kJ$