Exercise MCQS of Chemistry States
of Matter-Gases |Chapter –5
Matter consists of three states: solid, liquid, and gas. These are the principle states of matter. Gases have indefinite shape and indefinite volume. The molecules of gases are away from each other due to weak intermolecular forces present in them. Exercise MCQs of states of matter gases are below.
1. One dm^3 of hydrogen at STP weighs approximately
A. 0.0789g
B. 0.0799g
C. 0.0987g
D. 0.0899g
Correct option: D (0.0899g).
Explanation:
The volume of hydrogen is 22.71 L.
Molar mass of H2 = (2 x 1.008) = 2.016
1 dm^3 = 1 L
The mass of 1 mole of H2 is 2.016 g.
Therefore, 22.71 L of H2 weighs 2.016 g.
Hence, 1 L of H2 weighs (2.016 g/22.71 L)x1 L = 0.089 g.
2. Generally, a gas in a closed container will exert much higher pressure at the bottom due to gravity than at the top.
A. True
B. Untrue
C. In some cases,true, and in some cases, untrue
D. None
The correct option is B (untrue).
Explanation:
A gas in a closed container will not exert more pressure due to gravity at the bottom than at the top because the pressure is equal in all directions.
3. In a factory producing liquid air, one of the pipes carrying dry air at -80°C is blocked with a white solid. What is this white solid?
A. Oxygen
B. Nitrogen
C. Ice
D. Argon
Correct option: C (ice).
Explanation:
Carbon dioxide is a white solid called dry ice at temperatures below −78 °C. When heated to just above −78 °C, it changes into carbon dioxide gas.
4. A gas has a certain volume at 10°C. How much temperature should be raised to double its volume?
A. 566 k
B. 283k
C. 293 k
D. 283°C
Correct option: A (566k).
Explanation:
Temperature, T1 = 10°C
0 ℃ = 273 K, and 273 +10 °C =283 k.
So the gas equation is: P1V1/T1 = P2V2/T2.
Here, the pressure is constant. So P1 = P2 = P.
So, PV1/T1 = PV2/T2.
V1/T1 = V2/T2 –––——(1)
Now, double the volume: V2 = 2V1 and T1 = 283 K
Putting these values in (1),
V1/283 = 2V1/T2
So, T2 = 2 × 283 = 566 K.
5. The rate of diffusion of H2 compared with He is
A. 0.5 times
B. 1.4 times
C. 2 times
D. 4 times
Correct option: B (1.4 times).
Explanation:
The rate of diffusion is inversely proportional to molecular mass. As hydrogen have the lowest mass as compared to helium, So the rate of diffusion of hydrogen is 1.4 times greater than that of helium.
6. Hydrogen gas possesses K.E at the same temperature as compared to oxygen gas.
A. More
B. Less
C. Sometime less and sometime more
D. None
Correct option: D (none).
Explanation:
The K.E of the gas is directly proportional to the temperature of the gas. As the temperature of both gases is the same. So, the K.E of H2 and O2 is the same.
7. The molar volume of He is 44.8 dm3 at
A. 100°C and 1 atm
B. 25°C and 0.25 atm
C. 0°C and 0.5 atm
D. 40°C and 0.5 atm
Correct option: C (40°C and 0.5 atm).
8. At the same temperature and pressure, which of the following gases has the greatest density?
A. CO2
B. SO2
C. Cl2
D. H2O
Correct option: C (Cl2).
9. The number of atoms in 2 moles of CO2 is
A. 5.02 2 × 10^23
B. 12.04 x 10^ 23
C. 1.8132 × 10^34
D. 3.6132 × 10^24
Correct option: D (3.6132 × 10^24).
10. The value of the ideal gas constant in dm3 tor k-1 mole -1
A. 0.0821
B. 1.98722
C. 62.364
D. 8.3143
Correct option: C (62.364).
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