# Bond Energy Worksheet

Bond energy is used to describe the strenght of a bond in a chemical bond. In simple word it is a heat which is required in-order to break one Mole of a molecule into a individual atom. Bond strenght is directly related to bond lenght and bond distance.

Questions:

1. Which one of the following bonds h the highest average bond energy (kcal / mole)?

(a)    S = O

(b)   C = C

(c)    $C \equiv N$

(d)   $N \equiv N$

2. One mole of methanol, when burnt in oxygen gives out $723 kJ mol^{-1}$ heat. If one mole of oxygen is used, what will be the amount of heat evolved?

(a)    964 kJ

(b)   723 kJ

(c)    482 kJ

(d)   241 kJ

3. Given the bond energies of $N \equiv N$, H — H, and N — H bonds are 945, 436 and 391 $kJ mol^{-1}$ respectively, the enthalpy of the reaction $N_2(g) + 3H_2(g) \to 2NH_3(g)$ is:

(a)    -93 kJ

(b)   102 kJ

(c)    90 kJ

(d)   105 kJ

4. Energy required to dissociate 4 g of gaseous hydrogen into free gaseous atoms is 208 kcal at 25°C. The bond energy of H — H bond will be:

(a)    1040 kcal

(b)   104 kcal

(c)    10.4 kcal

(d)   1.04 kcal

5. values of heats of formation for and MgO are -48.4 and -34.7 kJ respectively. The heat of the reaction

$Mg + SiO_2 \to 2MgO + Si$ is:

(a) 13.7 Kj

(b)  21.0 Kj

(c)  1.37 Kj

(d)  -21.0 kj

6. The first ionization energy for Li is 5.4 eV and electron affinity of Cl is 3.61eV. The $\Delta H$ (in k]/mol) for the reaction $Li (g) + Cl (g) \to Li^+ + Cl^-$ is (if resulting ions do not combine with each other) ($1 eV = 1.6 \times 10^{-19J}$ )

(a)    17

(b)   20

(c)    100

(d)   270

7. The bond dissociation energies $H_2, Cl_2$ and HCl are 104, 58 and 103 kcal respectively. The enthalpy of formation of HCI is:

(a)    22 kcal

(b)   -22 kcal

(c)    44 kcal

(d)   -44 kcal