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JEE Advanced levelSingle correct optionDifficulty 3 of 3sc034

Two gases A and B follow Langmuir isotherms separately on the same surface at the same temperature, with $K_{A} = 0.50 kP a^{- 1}$ and $K_{B} = 0.20 kP a^{- 1}$ . Each gas is used alone at $6.0 kPa$ . The ratio $θ_{A} / θ_{B}$ is closest to:

A $2.50$
B $1.38$
C $1.00$
D $0.73$

Answer: B

θ_{A} = 3.0/4.0 = 0.750

and

θ_{B} = 1.2/2.2 = 0.545

. The ratio is

0.750/0.545 = 1.375 \approx 1.38

. The ratio

2.50

of the

K

values is wrong because coverage is not proportional to

K

once

K p

is not small.

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