MolSynapsequestion bank

MolSynapse / Question bank / Real Gases / Critical constants and liquefaction

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3rg036

Gas P has $T_{c} = 304 K$ , $P_{c} = 73 atm$ ; gas Q has $T_{c} = 126 K$ , $P_{c} = 34 atm$ . Both are treated as van der Waals gases. Which statements are correct?

AP is more easily liquefied than Q
BAt $300 K$ gas Q cannot be liquefied by pressure alone
CThe ratio $a_{P} / a_{Q}$ is about 2.7
DThe constant $b$ is larger for Q than for P

Answer: A, B, C

Higher

T_{c}

means stronger attraction and easier liquefaction (A true).

300 K

exceeds

T_{c}

of Q, so no pressure can liquefy Q there (B true).

a = 27 R^{2} T_{c}^{2} /64 P_{c}

, so

a_{P} / a_{Q} = (304/126)^{2} \times (34/73) = 5.822 \times 0.4658 = 2.71

(C true).

b = R T_{c} /8 P_{c}

:

b_{P} / b_{Q} = (304/126) (34/73) = 1.12

, so

b

is larger for P (D false).

Practice Real Gases More on Critical constants and liquefaction

Previous questionNext question

More questions on Critical constants and liquefaction