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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3sc055

Gases A and B adsorb competitively on the same sites (competitive Langmuir) with $K_{A} p_{A} = 2.0$ and $K_{B} p_{B} = 2.0$ . Which statements are correct?

AAdding B lowers $θ_{A}$ relative to A alone
B $θ_{A} + θ_{B} < 1$
C $θ_{A} = θ_{B} = 0.40$
D $θ_{A}$ is independent of $p_{B}$

Answer: A, B, C

A alone gives

θ_{A} = 2/3 = 0.667

. With both,

θ_{A} = θ_{B} = 2.0/ (1 + 2.0 + 2.0) = 0.40

, so total coverage

0.80 < 1

and A is lowered.

θ_{A}

depends on

p_{B}

through the denominator, so statement 4 is wrong.

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