Change set

Pick exam & year, then Go.

Question map
Not attempted Correct Incorrect ★ Bookmarked
Loading…
Q108 (UPPCS/2025) Science & Technology › Basic Science (Physics, Chemistry, Biology)

Which of the following gasses is/are lighter than air ?
1. Hydrogen chloride
2. Sulfur dioxide
3. Helium
Select the correct answer from the code given below :
Code :

Result
Your answer: —  Â·  Correct: A

Explanation

To determine if a gas is lighter than air, its molecular weight is compared to the average molecular weight of air, which is approximately 28.97 g/mol (composed mainly of Nitrogen and Oxygen).

  • Helium (He): Has an atomic weight of approximately 4 g/mol. Since 4 < 28.97, it is significantly lighter than air and is commonly used for buoyancy in balloons.
  • Hydrogen chloride (HCl): Has a molecular weight of approximately 36.5 g/mol (H=1, Cl=35.5). Since 36.5 > 28.97, it is heavier than air.
  • Sulfur dioxide (SO2): Has a molecular weight of approximately 64 g/mol (S=32, O=16 × 2). Since 64 > 28.97, it is much heavier than air.

Therefore, among the given options, only Helium is lighter than air.

How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
100%
got it right
✓ Thank you! We'll review this.

SIMILAR QUESTIONS

IAS · 2016 · Q86 Relevance score: -1.11

In the cities of our country, which among the following atmospheric gases are normally considered in calculating the value of Air Quality Index? 1. Carbon dioxide 2. Carbon monoxide 3. Nitrogen dioxide 4. Sulfur dioxide 5. Methane Select the correct answer using the code given below.

NDA-II · 2013 · Q63 Relevance score: -2.27

Which of the following statements is/are correct? 1. Air close to the Earth’s surface heavier. 2. Air close to the Earth’s surface contains larger quantity of water vapoor and dust particles Select the correct answer using the code given below :

CDS-I · 2018 · Q41 Relevance score: -2.41

Consider the following constituent gases of the atmosphere : 1. Argon 2. Neon 3. Helium 4. Carbon dioxide Which one of the following is the correct descending sequence of the above gases in terms of the volume percentage?