Question

Name two colourless gases.

Answer 1

Hydrogen gas and Oxygen gas are two colourless gases.

Evolution of Oxygen gas:

Potassium chlorate (KClO3) is heated in the presence of Manganese oxide (MnO₂) as a catalyst to form Potassium chloride (KCl) and Oxygen gas (O₂).

• A catalyst is a substance that increases the speed of a reaction.

$$\begin{gathered} 2{\mathrm{KClO}}_3\left(\mathrm{s}\right)\underset{∆}{\overset{{\mathrm{MnO}}_2}{\to }}2\mathrm{KCl}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right) \\ (\mathrm{Potassium}\mathrm{chlorate})(\mathrm{Potassium}\mathrm{chloride})\left(\mathrm{Oxygen}\right) \end{gathered}$$

Evolution of Hydrogen gas:

Zinc (Zn) displaces Hydrogen (H) from Sulphuric acid (H₂SO₄) to produce hydrogen gas.

$$\begin{gathered} \mathrm{Zn}\left(\mathrm{s}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ \left(\mathrm{Zinc}\right)(\mathrm{Sulphuric}\mathrm{acid})(\mathrm{Zinc}\mathrm{sulphate})\left(\mathrm{Hydrogen}\right) \end{gathered}$$

Distinguishing between Hydrogen and Oxygen:

In practical Chemistry, two types of analysis are done.

1. Qualitative analysis: The analysis which aims at detecting the presence of any substance in a given sample.
2. Quantitative analysis: The analysis which aims at knowing the quantity of any substance present in a sample.

The following two tests can help us to identify hydrogen and oxygen gas.

Rekindling of a splinter:

When oxygen gas comes in contact with a glowing splinter, it burns with a flame.

• A splinter is a long (approx. 6 inches) and a thin piece of wood.

As soon as the glowing splinter comes in contact with Oxygen gas, a flame can be seen as shown below. This is because oxygen supports the process of combustion or burning.

• Combustion is a process where a substance reacts with oxygen to release energy in the form of heat or light

Burning with a pop sound:

When a burning matchstick is brought near hydrogen gas, it produces a pop sound.