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JEE Main levelSingle correct optionDifficulty 2 of 3sc015

A gas obeys the Langmuir isotherm with $K = 0.040 kP a^{- 1}$ . The pressure at which half the surface sites are occupied is:

A $12.5 kPa$
B $50 kPa$
C $0.040 kPa$
D $25 kPa$

Answer: D

At

θ = 0.5

,

K p = 1

so

p = 1/ K = 1/0.040 = 25 kPa

. Using

1/ (2 K)

or

2/ K

are common slips.

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