1. Tardigrade
  2. Question
  3. Chemistry
  4. Using bond energy data, calculate heat of formation of isoprene 5C(s) + 4H2(g) → H2C = underset overset|CH3C - CH = CH2 Given C -H, H - H, C - C, C = C and C(s) → C(g) respectively as 98.8 kcal, 104 kcal, 104 kcal, 147 kcal, 171 kcal

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Q. Using bond energy data, calculate heat of formation of isoprene
$5C(s) + 4H_2(g) \to H_2C = \underset{\overset{|}{C}H_3}{C} - CH = CH_2$
Given $C -H, H - H, C - C, C = C$ and $C(s) \to C(g) $ respectively as $98.8\,kcal, 104\,kcal, 104\,kcal, 147\,kcal, 171\,kcal$

Thermodynamics

Solution:

Given
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$ \therefore \Delta H =(B . D . E)_{\text {reactants }}-(B . D . E)_{\text {products }} $
$=4 E_{H-H}-\left(2 E_{C=c}+8 E_{C-H}+E_{C-C}\right) $
$ \therefore \Delta H_{1} =5 x+\Delta H(\because H$ is a state function)
$ x=171 \,kcal $
$ \therefore \Delta H_{1} =5 \times 171 \,kcal +[4 \times 104\, kcal -(2 \times 147)-8 \times 98.8\, kcal ]-2 \times 83\, kcal $
$=855 \,kcal +(416\, kcal -294\, kcal -790.4 \,kcal -166\, kcal ) $
$=20.6\, kcal =21 \,kcal $