Chemical BondingMedium

Bond energy — bond length

Compare: C≡C (839 kJ/mol), C=C (614 kJ/mol), C-C (348 kJ/mol). Why is the triple bond shorter?

Given data

C≡C: 839 kJ/mol, 120 pmC=C: 614 kJ/mol, 134 pmC-C: 348 kJ/mol, 154 pm

Steps

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Strength ratio C≡C vs C-C: (839/348).
Write your working — the numerical result must appear in the text
Length ratio C-C vs C≡C: (154/120).

Full worked solution

Strength ratio C≡C vs C-C: (839/348).
$839/348$
$839/348 \approx 2.41 = \mathbf{2.41}$ . Triple bond is over 2× stronger.
Length ratio C-C vs C≡C: (154/120).
$154/120$
$154/120 \approx 1.283 = \mathbf{1.283}$ . Triple bond is 22% shorter.

Result:Triple bond is shorter (120 vs 154 pm) and much stronger (839 vs 348 kJ/mol).

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