Question

Energy required to dissociate $4g$ of gaseous hydrogen into free hydrogen atoms is $208Kcal$ at ${25^ \circ }C$ . The bond energy of $H - H$ bond will be:
A: $1.04Kcal$
B: $10.4Kcal$
C: $104Kcal$
D: $1040Kcal$

Answer 1

Hint : Bond energy is the measure of strength of bond. It is also called mean bond enthalpy or average bond enthalpy. Electronegativity of the two atoms bonding together affects the ionic bond energy.
Formula used: Dissociation energy$=$ number of moles$\times$ bond dissociation energy of one mole of molecule

Complete step by step solution :
Bond energy is determined by measuring the heat required to break one mole of molecules into their individual atoms.
Total dissociation energy given$= 208Kcal$
Mass of one mole of hydrogen atoms$= 2g$
Number of moles given$= \dfrac{4}{2} = 2$
Let dissociation energy of $H - H$bond be $x$
Put all these values in formula
$208 = 2 \times x \\\ x = 104 \\\$
Hence bond dissociation energy of $H - H$ bond is $104Kcal$ . So answer is option C i.e. $104Kcal$.
Additional information: There are four types of bonds in chemistry: Ionic, covalent, hydrogen, Vander waals interaction. Ionic bond is a bond that is formed between ions. Ions are the species that possess charge either positive or negative. Covalent bond is formed with sharing of electrons between two elements. It is the strongest and most common bond. Hydrogen bond is a bond between a hydrogen atom and an electronegative element. Electronegativity refers to the ability of an atom to attract shared electrons in covalent bonds. In water there is hydrogen bonding. Vander waal forces include attraction and repulsion between atoms, molecules, and surfaces as well as other intermolecular forces.

Note : Bond energy is defined as the sum of all bonds broken minus sum of all bonds formed
$\Delta H = \sum\limits_{}^{} {{H_{\left( {broken} \right)}} - \sum\limits_{}^{} {{H_{\left( {formed} \right)}}} }$
Energy is consumed when a bond breaks and energy is released when a new bond forms.