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1

NEET 2016 Phase 1

MCQ (Single Correct Answer)
Equal moles of hydrogen and oxygen gases are placed in a container with a pin-hole through which both can escape. What fraction of the oxygen escapes in the time required for onehalf of the hydrogen to escape?
A
3/8
B
1/2
C
1/8
D
1/4

Explanation

Let the number of moles of each gas = x

Fraction of hydrogen escaped = $${1 \over 2}x$$

$${{{r_{{O_2}}}} \over {{r_{{H_2}}}}} = \sqrt {{{{M_{{H_2}}}} \over {{M_{{O_2}}}}}} $$

$$ \Rightarrow {{{n_{{O_2}}}/t} \over {{x \over 2}/t}} = \sqrt {{2 \over {32}}} = \sqrt {{1 \over {16}}} = {1 \over 4}$$

$$ \Rightarrow {n_{{O_2}}} = {1 \over 8}x$$

Then, fraction of oxygen escaped = $${1 \over 8}$$
2

AIPMT 2015

MCQ (Single Correct Answer)
A gas such as carbon monoxide would be most likely to obey the ideal gas law at
A
low temperaures and high pressures
B
high temperatures and hgh pressures
C
low temperatures and low pressures
D
high temperature and low pressures.

Explanation

Real gas shows ideal gas behaviour at high temperature and low pressure.
3

NEET 2013

MCQ (Single Correct Answer)
Maximum deviation from ideal gas is expected from
A
CH4(g)
B
NH3(g)
C
H2(g)
D
N2(g)

Explanation

The compressibility factor is the term which is measured for a gas to study its deviation from the ideal behaviour. Compressibility factor,

$$Z = {{PV} \over {nRT}}$$

Greater is the difference in the value of Z from 1, greater is the deviation of the gas from ideal behaviour.

Among the given molecules, NH3 is easily liquefiable gas which deviates from ideal behaviour to the maximum extent.
4

NEET 2013 (Karnataka)

MCQ (Single Correct Answer)
What is the density of N2 gas 227oC and 5.00 atm. pressure? (R = 0.082 L atm K$$-$$1 mol$$-$$1)
A
1.40 g/mL
B
2.81 g/mL
C
3.41 g/mL
D
0.29 g/mL

Explanation

PV = nRT

$$ \Rightarrow $$ PV = $${W \over M}RT$$

$$ \Rightarrow $$ $$P = {W \over M} \times {{RT} \over V}$$

$$ \Rightarrow $$$$P = {{dRT} \over M}$$   [Density = $${{Mass} \over {Volume}}$$]

$$ \Rightarrow d = {{PM} \over {RT}} = {{5 \times 28} \over {0.0821 \times 500}} = 3.41\,g/ml$$

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