Question

The critical point of ${\mathbf{NH}}_{\mathbf{3}}$ is $\mathbf{132}\mathbf{°}\mathbf{C}$ and 111 atm, and thecritical point of role="math" localid="1663782837040" ${\mathbf{N}}_2\mathbf{}\mathbf{}\mathbf{}\mathbf{is}\mathbf{-}{\mathbf{147}}^0\mathbf{C}$ and 34 atm. Which of these substances cannot be liquefied at room temperature no matter how much pressure is applied? Explain.

Short answer

The ${\mathrm{N}}_2$cannot be liquefied at room temperature no matter how much pressure is applied.

Step-by-step solution

Describing the critical temperature and pressure

The critical temperature (Tc) of a gas is the temperature above which a gas cannot be liquefied whatever pressure is applied.

Critical pressure (Pc)is the pressure at which the vapor is liquefied at the critical temperature.

Above the critical point, the liquid phase transforms into the supercritical fluid.

The substances that cannot be liquefied at room temperature

The gas ${\mathrm{N}}_2$ has a critical temperature of $-147°\mathrm{C}$and 34 atm, and the NH₃ has $132°\mathrm{C}$ and 111 atm.

For liquefaction of any substance, the critical temperature must be greater than the room temperature, i.e., $25°\mathrm{C}$.The critical temperature of ${\mathrm{N}}_2$is less than the room temperature while has greater than the room temperature.

${\mathrm{NH}}_3$ can be liquefied at room temperature because it has a greater critical temperaturethan room temperature.

Therefore, the ${\mathrm{N}}_2$cannot be liquefied at room temperature no matter what pressure is applied.