Question

The internal energy change for the reaction CH4 + 2O2 + CO2 + 2H2O is -885 K/mol- at 298 k. what is enthalpy change (∆H) of the reaction?

(Class 11 ,chapter :- Thermodynamics)​

Answer 1

Answer : The enthalpy change of the reaction is -885000 J/mol

Explanation :

The balanced chemical reaction is,

$CH_4(g)+2O_2(g)\rightarrow CO_2(g)+2H_2O(g)$

Formula used :

$\Delta H=\Delta U+\Delta n_gRT$

where,

$\Delta H$ = change in enthalpy = ?

$\Delta U$ = change in internal energy = $-885kJ/mol=-885000J/mol$

$\Delta n_g$ = change in moles = [(2+1)-(2+1)] = 0 mol  (from the reaction)

R = gas constant = 8.314 J/mol.K

T = temperature = 298 K

Now put all the given values in the above formula, we get:

$\Delta H=\Delta U+\Delta n_gRT$

$\Delta H=(-885000J/mol)-[0mol\times 8.314J/mol.K\times 298K$

$\Delta H=-885000J/mol$

Therefore, the enthalpy change of the reaction is -885000 J/mol