Given, van der Waal's constant for ${\mathrm{NH}}_3,\mathrm{ }{\mathrm{H}}_2,\mathrm{ }{\mathrm{O}}_2$ and ${\mathrm{CO}}_2$ are respectively $4.17, 0.244, 1.36 \mathrm{and} 3.59$. Which one of the following gases is most easily liquefied?

• A

  ${\mathrm{O}}_2$
• B

  ${\mathrm{H}}_2$
• Correct answer
  C

  ${\mathrm{NH}}_3$
• D

  $C{O}_2$

Hence, the correct answer is option: 'C'.