Calculate the enthalpy change accompanying the transformation of C(graphite) to C(diamond). Given that the enthalpies of combustion of graphite and diamond are 393.5 and 395.4 kJ mol–1 respectively.

Question

Shiksha Nation · Accepted Answer

Enthalpy of Transition Solution
    
        body {
            font-family: "Times New Roman", Times, serif;
            font-size: 16px;
            line-height: 1.8;
            color: #000000;
            margin: 30px;
        }
        .line-item {
            margin-bottom: 20px;
        }
        .equation-block {
            margin-left: 40px;
            margin-top: 15px;
            margin-bottom: 15px;
        }
        sup {
            font-size: 0.75em;
        }
        sub {
            font-size: 0.75em;
        }

Sol: We are given

(i)   C(graphite) + O2(g) &rarr; CO2(g); &Delta;cH&deg; = &minus;393.5 kJ mol&minus;1

(ii)  C(diamond) + O2(g) &rarr; CO2(g); &Delta;cH&deg; = &minus;395.4 kJ mol&minus;1

We aim at C(graphite) &rarr; C(diamond), &Delta;transH&deg; = ?

Subtracting equation (ii) from equation (i) we get

C(graphite) &minus; C(diamond) &rarr; 0; &Delta;rH&deg; = &minus;393.5 &minus; (&minus;395.4) = +1.9 kJ

C(graphite) &rarr; C(diamond) ; &Delta;transH = +1.9 kJ

Calculate the enthalpy change accompanying the transformation of C(graphite) to C(diamond). Given that the enthalpies of combustion of graphite and diamond are 393.5 and 395.4 kJ mol^–1 respectively.

Verified Answer