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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3sc051

A gas obeys the Langmuir isotherm with $K = 0.125 kP a^{- 1}$ . Which statements are correct?

A $θ = 0.50$ at $8.0 kPa$
B $90%$ coverage requires $72 kPa$
CThe pressure for $90%$ coverage is twice that for $75%$ coverage
D $θ = 0.83$ (approximately) at $40 kPa$

Answer: A, B, D

θ (8) = 1/2

and

θ (40) = 5/6 = 0.83

.

p_{0.9} = 0.9/ (0.125 \times 0.1) = 72 kPa

and

p_{0.75} = 24 kPa

, so the ratio is

3

, not

2

. Statements 1, 2 and 4 are correct.

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