Question

Using the data provided, calculate the multiple bond energy (\[KJmo{{l}^{-1}}\]) of a \[C\equiv C\] bond in \[{{C}_{2}}{{H}_{2}}\]. That energy is:
(take the bond energy of a \[C-H\]bond as 350 \[KJmo{{l}^{-1}}\])
\[2C(s)+{{H}_{2}}(g)\to {{C}_{2}}{{H}_{2}}(g)\]; \[\Delta H=225KJmo{{l}^{-1}}\]
\[2C(s)\to 2C(g)\]; \[\Delta H=1410KJmo{{l}^{-1}}\]
\[{{H}_{2}}(g)\to 2H(g)\]; \[\Delta H=330KJmo{{l}^{-1}}\]
A. 1165
B. 837
C. 865
D. 815

Answer 1

Hint: Bond energy of a chemical bond in a compound is the average value of all the bond dissociation enthalpies of that bond in the molecule and it is also known by some other names called mean bond enthalpy or average bond enthalpy which generally used to measure the strength of bond.

Complete Solution :
Bond energy is energy required to dissociate the bonds. The bond dissociation energy can be calculated by the difference between bond energy of products and reactants. Bond energy is the average of all bond-dissociation energies of a single type of bond in a given molecule. The bond-dissociation energies of different bonds of the same type can vary even within a single molecule. When the bond is broken the bonding electron pair will split equally into the products. This process is called homolytic bond cleavage and results in the formation of radicals. Metallic radius, ionic radius, and covalent radius of each atom in a molecule can be used to determine the bond strength.

\[\Delta H={{(bond~energy)}_{R}}-{{(bond~energy)}_{P}}\]
\[225=[(1410+330)-(\Delta {{H}_{C\equiv C}}+2\times 350)]\]
\[\Delta {{H}_{C\equiv C}}=[1515-700]\]
\[\Delta {{H}_{C\equiv C}}=815Kjmo{{l}^{-1}}\]
So, the correct answer is “Option D”.

Note: Bond energy depends on many factors like the electronegativity of the two atoms bonding together affects ionic bond energy. The farther away the electronegativity of two atoms the stronger is the bond generally. And mostly ionic bonds are stronger than covalent bonds. By looking at melting points, ionic compounds have high melting points and covalent compounds have low melting points.