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Question 3.8: Calculate the standard heat of the following reaction, given...

Calculate the standard heat of the following reaction, given the enthalpies of formation:

4NH_{3} \left(g\right)+5O_{2} \left(g\right)\longrightarrow 4NO\left(g\right)+6H_{2}O\left(g\right)

Standard enthalpies of formation kJ/mol

NH_{3}(g)                 -46.2
NO (g)                     +90.3
H_{2}O(g)                 -241.6

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Note: the enthalpy of formation of O_{2} is zero.

\Delta H^{°}_{r}=\sum{\Delta H^{°}_{⨍}}, products – \sum{\Delta H^{°}_{⨍}} ,reactants
= (4 × 90.3 + 6 × (-241.6)) – (4 × (-46.2))
=\underline{\underline{-903.6 kJ/mol} }
Heat of reaction – \Delta H^{°}_{r} = \underline{\underline{904 kJ/mol} }

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