Question

35. C(diamond) + O2 --CO2 AH = -398 kJ
C(graphite) +O2→ CO2 AH = -395 kJ
the heat liberated when 1g diamond is converted to 1g graphite is
1) 3 kJ
2-3 kJ
3) 250J
4)-250J
please show me the answer with explanation​

Answer 1

Given

(CD+O2→CO2(g),ΔH=-94.3kcal...(i)),(CA+O2→CO2(g),ΔH=97.6kcal...(ii)),

Subtracting equation (ii) from equation (i),

CD-CA→O,ΔH=+3.3

or CD→CA,ΔH=+3.3kcal

i.e. heta of transition for CD→CA=+3.3kcal

Also 12gCD changes to CA with heat change =+3.3kcal

∴1gofCD change to CA with heat change

=+3.3/12kcla=0.275kcal