Question

Estimate the heat released when ethene (CH₂ CH₂) reacts with HBr to give CH₃CH₂Br. Bond enthalpies are 

C- H : 412 kJ/mol; C- C : 348 kJ/mol; 

C= C : 612 kJ/mol; C- Br : 276 kJ/mol; 

Br -Br : 193 kJ/mol; H- Br : 366 kJ/mol.

1. 200 kJ/mol 

2. 424 kJ/mol 

3. 58 kJ/mol 

4. 1036 kJ/mol 

5. 470 kJ/mol

Answer 1

Correct option (3) 58 kJ/mol

Explanation:

= (612 kJ/mol + 366 kJ/mol)

− [412 kJ/mol + 276 kJ/mol + 348 kJ/mol]

= −58 kJ/mol ,