The value of `Delta H` for the reaction
`2 N_(2)(g) + O_(2) (g) rarr 2N_(2) O (g)`
at `298 K` is `164 kJ`. Calculate `Delta U` for the reaction.
Strategy : In this process, 3 mol of gas change to 2 mol of gas at constant temperature and pressure. Assuming ideal gas behavior, we can use. First `Delta_(n_(g))` and the obtain a value of `Delta U` by converting the value of `Delta H` from `164 kJ` to `164000 J` and expressing `R` in units of `J mol^(-1) K^(-1)`

Explanation

`Delta_(n_(g))` = (Total moles of gas products) - (Total moles of gas reactants)
`= (2 mol) - (3 mol)`
`= - mol`
From , we write
`Delta U = Delta H - (Delta_(n_(g))) RT`
`(164000 J) - (-1 mol) (8.314 J mol^(-1) K^(-1)) (298 K)`
`= 161522 J = 162 kJ`