Given that the average bond energies for C-H and C-Br bonds are 413 and 276 kJ/mol,respectively,the heat of atomization of bromoform (CHBr₃)is ________ kJ/mol. A)1241 B)689 C)-689 D)1378 E)-1378

Question

Quizplus · Accepted Answer

The heat of atomization can be calculated by breaking all the bonds in the molecule into their constituent atoms and calculating the energy required to do so.

Heat of atomization = sum of bond energies broken - sum of bond energies formed

In bromoform, there are 3 C-H bonds and 1 C-Br bond that need to be broken.

Energy required to break 3 C-H bonds = 3 × 413 kJ/mol = 1239 kJ/mol

Energy required to break 1 C-Br bond = 276 kJ/mol

Total energy required to break all bonds = 1239 + 276 = 1515 kJ/mol

Since we are breaking bonds, the heat of atomization is negative.

Heat of atomization of bromoform = -1515 kJ/mol

Therefore, the closest answer choice is A) 1241 kJ/mol, which is the rounded absolute value of -1515 kJ/mol.

Given That the Average Bond Energies for C-H and C-Br