Question

Molecular mass of Benzene is ……………..g/mol
A. 72
B. 78
C. 79
D. 77

Answer 1

Hint- Here we will proceed by determining the steps to find the molecular mass of a compound so that we know how to find the molecular mass of a given compound i.e., benzene ${C_6}{H_6}$.

Complete answer:
Benzene- Benzene is a clear, colorless, highly inflammable and volatile, liquid aromatic hydrocarbon with a gasoline like odor. The molecular formula of benzene is ${C_6}{H_6}$. The elements included in Benzene are carbon and hydrogen.
Firstly, we must know the steps to find the molecular mass of a compound.
Step1- Determine the molecular formula of the molecule.
Step2- Use the periodic table to determine the atomic mass of each element in the molecule.
Step3- Multiply each element’s atomic mass by the number of atoms of that element in the molecule. This number is represented by the subscript next to the element symbol in the molecular formula.
Step4- Add these values together for each different atom in the molecule.
Now applying these steps, we will find the molecular mass of benzene.
Step1- The molecular formula of benzene is ${C_6}{H_6}$.
Step2- As we know that elements of compound benzene are Carbon and hydrogen.
 Atomic mass of carbon- C:12.01 g/mol
Atomic mass of hydrogen- H:1.01 g/mol
Step3- There are 6 atoms of both the elements of Benzene.
Carbon- $12.011{\text{ g/mol}} \times {\text{6 = 72}}{\text{.066 g/mol}}$
Hydrogen-$1.008{\text{ g/mol}} \times {\text{6 = 6}}{\text{.048g/mol}}$
Step4- Adding these values,
 72 g/mol + 6 g/mol
We get-
78 g/mol.

Therefore, Molecular mass of Benzene is 78 g/mol.

Hence, option B is correct.

Note- In order to solve this question, we must know all the physical properties and chemical properties of Benzene ${C_6}{H_6}$. Also we must know the structure of benzene to solve all questions related to compound benzene ${C_6}{H_6}$.