States Of Matter(12th Grade > Chemistry ) Questions and answers for exam Preparation

12th Grade > Chemistry

STATES OF MATTER MCQs

Total Questions : 30 | Page 1 of 3 pages

Question 1. A cubical vessel has a side with 'I' cm lenth contained a gas at a pressure of 'p'. when the side of the vessel is made

\frac{1}{2}

cm, the pressure of gas becomes?

Discuss Question

Answer: Option D. -> 8P
:
D

P_{1}

V_{1}

P_{2}

V_{2}

l^{3}

p_{2}

{(\frac{1}{2})}^{3}

P_{2}

= 8P

Question 2. The temperature above which gas cannot be liquefied by application of pressure alone is

Boyle temperature
Curie temperature
Critical temperature
None of the above

Discuss Question

Answer: Option C. -> Critical temperature
:
C
This is the definition of critical temperature.

Question 3. Pressure of a mixture of 4 g of O₂ and 2 g of H₂ confined in a bulb of 1 litre at 0°C is___.

25.215 atm
31.205 atm
45.215 atm
15.210 atm

Discuss Question

Answer: Option A. -> 25.215 atm
:
A
No. of moles of

O_{2} = \frac{4}{32} = 0.125

No.of moles of

H_{2} = \frac{2}{2} = 1

Total no. of moles = 1+0.125 = 1.125

P = \frac{n R T}{V} = \frac{1.125 \times 0.082 \times 273}{1} = 25.215 a t m

Question 4. Helium atom is two times heavier than a hydrogen molecule at 298 K, the average kinetic energy of helium is

Two times that of a hydrogen molecule
Same as that of a hydrogen molecule
Four times that of a hydrogen molecule
Half that of a hydrogen molecule

Discuss Question

Answer: Option B. -> Same as that of a hydrogen molecule
:
B

\frac{E_{H e}}{E_{H_{2}}} = \sqrt{\frac{T_{H_{e}}}{T_{H_{2}}}}

so energies will be same for
He &

H_{2}

at same temperature.

Question 5. In which of the gases given below, the average speed of the molecule is the least at 1000K?

Discuss Question

Answer: Option B. -> SO2
:
B
Speed is inversely proportional to molecular weight. Molecular weight of

S O_{2}

is highest among the four. Hence its speed is least.

Question 6. The density of Ne is maximum at

STP
0∘C, 2atm
273∘C, 1 atm
273∘C, 2 atm

Discuss Question

Answer: Option B. -> 0∘C, 2atm
:
B
For an ideal gas, density(d) will be the maximum when Pressure is high and the temperature is low.

d = \frac{P M}{R T} (o r) d \propto \frac{P}{T}

Therefore option B is correct as it satisfies these conditions.

Question 7. The density of vapour of a substance (X) at 1 atm pressure and 500 K is 0.8

\frac{k g}{m^{3}}

. The vapour effuses through a small hole at a rate of

\frac{4}{5}

times slower than oxygen under the same condition. What is the compressibility factor (Z) of the vapour?

0.974
1.35
1.52
1.22

Discuss Question

Answer: Option C. -> 1.52
:
C

\frac{r_{x}}{r_{O_{2}}} = \sqrt{\frac{M_{O_{2}}}{M_{x}}} = ⟮ \frac{4}{5} ⟯^{2} = \frac{32}{M_{x}} \Rightarrow M_{x} = 50

d_{x} = 0.80 k g m^{- 3}

V_{m} = \frac{1000}{800} \times 50 = 62.5 L

Z = \frac{P V_{m}}{R T} = \frac{1 \times 62.5}{0.0821 \times 500} = 1.52

Question 8. The ratio of the rate of diffusion of helium and methane under identical condition of pressure and temperature will be___.

Discuss Question

Answer: Option B. -> 2
:
B

\frac{r_{H e}}{r_{C H_{4}}} = \sqrt{\frac{M_{C H_{4}}}{M_{H e}}} \Rightarrow \sqrt{(} \frac{16}{4}) \Rightarrow 2

Question 9. According to kinetic theory of gases, for a diatomic molecule

The pressure exerted by the gas is proportional to the mean velocity of the molecules
The pressure exerted by the gas is proportional to the root mean square velocity of the molecules
The root mean square velocity is inversely proportional to the temperature
The mean translational kinetic energy of the molecules is proportional to the absolute temperature

Discuss Question

Answer: Option D. -> The mean translational kinetic energy of the molecules is proportional to the absolute temperature
:
D
All molecules of an ideal gas show random motion. They collide with each other and walls of container during which they lose or gain energy so they may not have same kinetic energy always.

Question 10. A sample of