Question

How will you show that air is dissolved in water?

Answer 1

Hint: Water is a chemical compound, which is colourless, odourless and tasteless. It is made up of $2\;moles$ of hydrogen and $1\;mole$ of oxygen. Since the question says ‘show’ that air is present in water, we need to give an experiment.

Complete step by step answer:
Water is a universal solvent which can dissolve almost any other substance in it. It is a colourless, odourless and tasteless liquid at room temperature. It has the chemical formula $H_{2}O$. It is made up of $2\;moles$ of hydrogen and $1\;mole$ of oxygen. Thus clearly it is made up of air.

2H$_2$+O$_2$ $\longrightarrow$ 2H$_2$O

To show that it is made up of air, we can try an easy experiment as follows.
In a vessel, take some water and observe it. Now boil the water. What do you observe?
We see that there are bubbles in the vessel containing water. These bubbles are formed due to the expulsion of air which was dissolved in the water.
Due to the increase in temperature, the solubility of gases in water decreases. The increase in temperature increases the kinetic energy of the molecules, resulting in breaking of intermolecular bonds.
And hence, the air dissolved in the water is expelled out.

Additional Information
The atmosphere contains about 21% of oxygen, whereas about 36% of oxygen is present in the water.

Note:
Water is made up of oxygen and hydrogen, which is also present in air. However to show that air is present in the water, we need an visual proof like experiment. Also it is worth remembering the balanced equation of the formation of water.