Question

Molecular weight of phenol is

• A. $94.11\mathrm{g}{\mathrm{mol}}^{-1}$
• B. $84.11\mathrm{g}{\mathrm{mol}}^{-1}$
• C. $104.11\mathrm{g}{\mathrm{mol}}^{-1}$
• D. $98\mathrm{g}{\mathrm{mol}}^{-1}$

Answer 1

The correct option is A

$94.11\mathrm{g}{\mathrm{mol}}^{-1}$

Explanation for correct option:

Option (a): $94.11\mathrm{g}{\mathrm{mol}}^{-1}$

Molecular weight: Molecular weight is the sum of the masses of the atoms in a molecule.

Given compound: Phenol (${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$)

Step 1: Analyzing atomic masses of atoms involved in the compound.

• Atomic mass of$\mathrm{H}=1.00784\mathrm{u}$
• Atomic mass of$\mathrm{C}=12.011\mathrm{u}$
• Atomic mass of $\mathrm{O}=15.999\mathrm{u}$

Step 2: Determining molecular weight of the compound.

Molecular mass of ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$

$$\begin{gathered} =(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{C})\mathrm{x}6+(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{H})\mathrm{x}6+(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{O}) \\ =(12.011\mathrm{x}6)+(1.00784\mathrm{x}6)+15.999 \end{gathered}$$

$=94.11204\mathrm{g}{\mathrm{mol}}^{-1}$

Hence, the Molecular weight of ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$ is $94.11204\mathrm{g}{\mathrm{mol}}^{-1}$