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WBJEEUsing the data provided, calculate the multiple bond energy (kJmol−1) of a...
Using the data provided, calculate the multiple bond energy (kJmol−1) of a C≡C bond in C2H2. That energy is (take the bond energy of a C−H bond as 350 kJ mol−1 ) 2C(s)+H2( g)⟶HC=CH(g);ΔH=225 kJ mol−1 2C(s)⟶2C(g);ΔH=1410 kJ mol−1 H2( g)⟶2H(g);ΔH=330 kJ mol−1
Solution:
(i) 2C(s)+H2( g)⟶H−C≡C−H(g)
ΔH=225 kJ mol−1
(ii) 2C(s)⟶2C(g)ΔH=1410 kJ mol−1
(iii) H2 (g) ⟶2H (g) ΔH=330 kJ mol−1
From equation (i) :
$225=[2×ΔHC(s)⟶C(g)+1×BEH−H]−[2×BEC−H+1×BEC≡C]225=[1410+1×330]−[2×350+1×BEC≡C]225=[1410+330]−[700+BEC≡C]225=1740−700−BEC≡CBEC≡C=815 kJ mol−1$
ΔH=225 kJ mol−1
(ii) 2C(s)⟶2C(g)ΔH=1410 kJ mol−1
(iii) H2 (g) ⟶2H (g) ΔH=330 kJ mol−1
From equation (i) :
$225=[2×ΔHC(s)⟶C(g)+1×BEH−H]−[2×BEC−H+1×BEC≡C]225=[1410+1×330]−[2×350+1×BEC≡C]225=[1410+330]−[700+BEC≡C]225=1740−700−BEC≡CBEC≡C=815 kJ mol−1$
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