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

Question

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 (A) - 21 kcal (B) 21 kcal (C) 40 kcal (D) 50 kcal

Tardigrade Admin · Accepted Answer

Given <img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/chemistry/920c9bc105c5796e4f708d6bcc907f37-.png" /> ∴ Δ H =(B . D . E) text reactants -(B . D . E) text products =4 EH-H-(2 EC=c+8 EC-H+EC-C) ∴ Δ H1 =5 x+Δ H(∵ H is a state function) x=171 kcal ∴ Δ H1 =5 × 171 kcal +[4 × 104 kcal -(2 × 147)-8 × 98.8 kcal ]-2 × 83 kcal =855 kcal +(416 kcal -294 kcal -790.4 kcal -166 kcal ) =20.6 kcal =21 kcal

Q. Using bond energy data, calculate heat of formation of isoprene 5C(s)+4H2​(g)→H2​C=C∣H3​C​−CH=CH2​ Given C−H,H−H,C−C,C=C and C(s)→C(g) respectively as 98.8kcal,104kcal,104kcal,147kcal,171kcal

- 21 kcal

21 kcal

40 kcal

50 kcal

Given ∴ΔH=(B.D.E)reactants ​−(B.D.E)products ​ =4EH−H​−(2EC=c​+8EC−H​+EC−C​) ∴ΔH1​=5x+ΔH(∵H is a state function) x=171kcal ∴ΔH1​=5×171kcal+[4×104kcal−(2×147)−8×98.8kcal]−2×83kcal =855kcal+(416kcal−294kcal−790.4kcal−166kcal) =20.6kcal=21kcal

Q. Using bond energy data, calculate heat of formation of isoprene
$5 C (s) + 4 H_{2} (g) \to H_{2} C = C ∣ H_{3} C - C H = C H_{2}$
Given $C - H, H - H, C - C, C = C$ and $C (s) \to C (g)$ respectively as $98.8 k c a l, 104 k c a l, 104 k c a l, 147 k c a l, 171 k c a l$