Chemistry · Physics

Gases and Gas Laws

298 Questions

The study of gases and gas laws involves understanding the relationships between pressure, volume, and temperature of gases. This topic is essential for chemistry and physics sections in many competitive exams. Practice these questions to master concepts like the ideal gas law, partial pressure, and molecular properties.

Ideal gas law calculationsGas volume and pressureStoichiometry of gasesDensity of gasesBoltzmann constant applicationsThermal speed of sound

Gases and Gas Laws Questions

Multiple choice general knowledge science & technology

One kg of air is compressed from 1 m3 to 0.5 m3. Which of the following statements is true?

  1. The density is halved

  2. The mass is doubled

  3. The density is doubled

  4. The mass is halved
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Density is mass divided by volume. When the volume is reduced to half while the mass remains constant, the density must double. The initial density of 1 kg/m³ becomes 2 kg/m³ after compression.

Multiple choice general knowledge

What is the acceptable level of CO2 in the atmosphere

  1. 400 PPM

  2. 350 PPM

  3. 300 PPM

  4. 375 PPM
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

350 PPM (parts per million) is considered the safe upper limit for CO2 concentration in the atmosphere to maintain climate stability. Beyond this level, risks of dangerous climate change increase significantly. The question reflects climate science concerns from the 2000s when this target was actively discussed. Current levels exceed 400 PPM.

Multiple choice general knowledge

SCUBA divers cannot pass gas (i.e. fart) at depths of 33 feet or below.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is a myth. While gas compression occurs at depth due to increased water pressure, the gas in the digestive tract does compress but does not prevent flatulence. In fact, some divers report increased gas due to pressure changes affecting digestion. At depth, compressed gas would actually be smaller in volume than at the surface.

Multiple choice general knowledge

The Authority of Pollution Control sets the permissible level of CO2 emmissions to 10mg/l. If for Calibration, GM sets the permissible level to 5mg/l, what will be the worst passing and best failing values in this case, respectively?

  1. 9, 12

  2. 11,12

  3. 10,12

  4. 13,12
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

GM sets calibration to 5mg/l. Worst passing value would be 5 + 10% of 5 = 5.5mg/l (at the upper edge of passing). Best failing value would be just above 5.5mg/l. But wait, the question mentions the Authority sets 10mg/l as permissible. Re-reading: if calibration is 5mg/l, and we need to find worst passing and best failing values relative to the calibration standard... With 10% tolerance: passing range is 4.5-5.5mg/l. Worst passing = 5.5mg/l. But that's not in the options. Let me reconsider... Ah, maybe the question is asking about values relative to the Authority's 10mg/l limit? If GM sets 5mg/l internally, and Authority allows 10mg/l, then worst passing at Authority level could be 9mg/l (still under 10), and best failing could be 11-12mg/l (above 10). The option shows 9, 12 which means: 9mg/l passes (under 10mg/l Authority limit), 12mg/l fails (above 10mg/l). This interpretation makes sense.

Multiple choice

A flask of 10-3 m3 volume contains 3 x 1022 molecules of oxygen at a certain temperature. The mass of one molecule of oxygen is 5.3 x 10-26 kg and rms velocity of its molecules at the same temperature is 400m/s. Calculate the pressure of the gas.

  1. 8.48 x 104 N/m2

  2. 25.44 x 104 N/m2

  3. 636 N/m2

  4. 212 N/m2

  5. 2.12 x 10-4 N/m2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pressure of the gas P = (1/3)(mN/V)v2 rms Here  V =10-3m3 N = 3 x 1022 m = 5.3 x 10-26 kg v rms = 400 m/s ∴ P = (1/3){ 5.3 x 10-26 x 3 x 1022 (400)2}/10-3        = 8.48 x 104 N/m2

Multiple choice

What will be the volume occupied by 5.0 gm of nitrogen at 27oC and 750 mm Hg pressure?

  1. 4.225 litres

  2. 4.451 litres

  3. 5.253 litres
    1. 951 litres

  5. 6.234 litres
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given is P = 750 mm =750/760 atm
V = ?,  W = 7.0 gramT = 27o C = 27+ 273 = 300o KR = 0.082, Molecular wt. M = 28. According to ideal gas equation PV = w/M x R x T                                         V = (w x R x T)/(M x P) Substituting the values in this eq.                                              V = (5 x 760 x 0.082 x 300)/(28 x 750)                                                  = 4.451 litres.

Multiple choice

A box contains one gram hydrogen gas, four grams helium gas, seven grams nitrogen gas and eight grams of oxygen gas. Which of the gas will have high partial pressure?

  1. Hydrogen gas

  2. Oxygen gas

  3. Helium gas

  4. Nitrogen gas

  5. All of them exerts equal pressure.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pressure is directly proportional to moles of gases.  4 grams of He = 1 mole of He gas (weight/molar weight); highest among all. Molecular weight of Helium gas is 4.