Question

Which of the following gaseous mixtures can be separated by using $\mathrm{KOH}$ as a solvent?

• A. ${\mathrm{CO}}_2\mathrm{and}{\mathrm{SO}}_2$
• B. ${\mathrm{N}}_2\mathrm{and}{\mathrm{NH}}_3$
• C. ${\mathrm{CO}}_2\mathrm{and}{\mathrm{NH}}_3$
• D. ${\mathrm{H}}_2\mathrm{and}{\mathrm{N}}_2$

Answer 1

The correct option is D

${\mathrm{H}}_2\mathrm{and}{\mathrm{N}}_2$

Explanation for the correct option: (D)

• Polar solvents contain bonds between atoms with very different electronegativities, such as oxygen and hydrogen, and have large dipole moments (also known as "partial charges"). Bonds between atoms with similar electronegativities, such as carbon and hydrogen, exist in nonpolar solvents (think hydrocarbons, such as gasoline).
• According to the like dissolve-like rule, a non-polar molecule dissolves in a nonpolar solvent or vice versa, and the molecule which dissolves can be separated out by the solvent. In other words, a solution's dissolved solute will not settle out or separate from the solvent.
• The given solvent, $\mathrm{KOH}$ (Potassium hydroxide) is a non-polar solvent.
• Among all the given options, the mixture of nitrogen and hydrogen gases dissolves in a non-polar solvent which is potassium hydroxide as they both are non-polar.

Explanation for the incorrect options:

A. In${\mathrm{CO}}_2\mathrm{and}{\mathrm{SO}}_2$, carbon dioxide $\left({\mathrm{CO}}_2\right)$ is non-polar and sulfur dioxide $\left({\mathrm{SO}}_2\right)$ is polar. So, it can not be separated out by the solvent.

B. In${\mathrm{N}}_2\mathrm{and}{\mathrm{NH}}_3$, nitrogen $\left({\mathrm{N}}_2\right)$ is non-polar and ammonia $\left({\mathrm{NH}}_3\right)$ is polar. So, it can not be separated out by the solvent.

C. In${\mathrm{CO}}_2\mathrm{and}{\mathrm{NH}}_3$, carbon dioxide $\left({\mathrm{CO}}_2\right)$ is non-polar and ammonia $\left({\mathrm{NH}}_3\right)$is polar. So, it can not be separated out by the solvent.

Conclusion: Hence, the correct option is D.