ESS
Grade-6
Easy

Question

What is the percentage of oxygen in air?

  1. 20%
  2. 21%
  3. 78%
  4. 70%

hintHint:

The most abundant gas is nitrogen which is 78%.

The correct answer is: 21%


    The correct option is b)21%
    It's a mixture of different gases. The air in Earth's atmosphere is composed of approximately 78% nitrogen and 21% oxygen. Air also contains small amounts of other gases such as carbon dioxide, neon, and hydrogen. Tiny organisms known as cyanobacteria, or blue-green algae. These microorganisms carry out photosynthesis. It uses sunlight, water and carbon dioxide to produce carbohydrates and oxygen.