1 gram of graphite is burnt in a bomb calorimeter in excess of oxygenat 298 K and 1 atm pressure according to the equation : C (graphite) + O2 (g) → CO2 (g).During the reaction temperature rises from 298 to 299 K. If the heat capacity of the bomb calorimeter is 20.7 kJ/K then what is the enthalpy change for the above reaction at 298 K and 1 atm?


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Given:

\(C_{(s)}+O_{2(g)}\rightarrow CO_{2(g)}\)

\(\Delta n_g=1-1=0\)

weight of  C =1

T1=298

T2=299

Cv=20.7 KJ/k

\(\Delta h=?\)

\(mol=\frac{1}{12}\)

We know

\(\Delta H=\Delta E+\Delta n_g RT\)

Where \(\Delta n_g=0\)

So, \(\Delta H=\Delta E\) ........(1)

Heat evolved at constant volume

\(q_v= - C_v \Delta T=-20.7\times(299-298)\\=-20.7\times1=-20.7KJ\)

\(\frac{q_v}{n}=\Delta E\)(for 1mol)

\(\Delta E=\frac{-20.7}{\frac{1}{12}}\\=-20.7\times12\)

\(\Delta E=-20.7\times12\,KJ/mol\)

From equation (1)

\(\Delta H=\Delta E=-20.7\times12\,KJ/mol\\=-248.4\,KJ/mol\)

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