Use the bond enthalpies given to estimate the heat released when 2-methyl-1-propene, (CH₃) ₂C=CH₂,
Reacts with HBr to give (CH₃) ₂CBrCH₃.Bond enthalpies ( kJ.mol^-1) :C-H,412; C-C,348;C=C,612; C-Br,276; H-Br,366.

Question

Quizplus · Accepted Answer

The heat released is calculated by subtracting the bond enthalpies of bonds formed from the bond enthalpies of bonds broken. For this reaction, one C=C (612 kJ/mol) and one H-Br (366 kJ/mol) bond are broken, and one C-C (348 kJ/mol), one C-Br (276 kJ/mol), and one H-H (which is not given but typically around 436 kJ/mol) bond are formed. The calculation is (612 + 366) - (348 + 276 + 436) = 58 kJ/mol, indicating that 58 kJ/mol is released.

Use the Bond Enthalpies Given to Estimate the Heat Released