Question

What is the abundance of oxygen in the Universe?
A) Most common element, by mass
B) ${{3}^{rd}}$ Most common element, by mass
C) ${{5}^{th}}$ Most abundant element by mass
D) Oxygen is relatively rare in the Universe

Answer 1

Hint: Abundance of elements is the measure of occurrence of the element with respect to the remaining elements in the given chemical environment. Many reactions and natural phenomena produce oxygen.

Complete step by step solution:
The abundance as mentioned earlier is the measure of occurrence of the element compared with the other elements for the given environment. Abundance can be calculated using three ways,
-Mass-fraction
-Mole –fraction
-Volume-fraction

-Abundance by mass –fraction is the ratio of the mass of the chemical element to the total mass of mixture.
- If we see the most abundant gas in the Universe it is Hydrogen of about 739000 ppm and next is helium 240,000 pm and then comes the oxygen which is 10,400 ppm.
- So from the data it is clear that hydrogen and helium are the most abundant gases and oxygen is the third most abundant gas with respect to mass. That is why oxygen is considered as the most important gas in the cloud composition and in dust storms etc. Oxygen is the most important gas for life processes and it is about 21% in percentage composition in the atmosphere and hydrogen is about 79%.

Additional Information:
Oxygen is the most important gas for living as without oxygen one cannot live for even a few minutes. Not only humans but all living things like flora and fauna too require oxygen for various life processes. Oxygen is the ${{8}^{th}}$ element in the periodic table with 4 electrons in the valence shell.
So, the correct answer is “Option A”.

Note: Students may get confused with hydrogen and oxygen since oxygen is the gas that sustains life but the hydrogen is the abundant gas comparing the whole Universe.