Laboratory Preparation of Hydrogen Gas

The laboratory preparation of hydrogen gas usually involves the action of dilute sulphuric acid or dilute hydrochloric acid on zinc granules. Granulated zinc is ideal for the preparation of hydrogen gas in chemical laboratories because it usually contains a small amount of copper, which has the ability to act as a catalyst for the associated chemical reaction and, therefore, increases the rate of the chemical reaction without actually participating in it. An experimental procedure for the laboratory preparation of hydrogen gas is provided below.

Procedure for the Laboratory Preparation of Hydrogen Gas

• Step 1: Take a few grams of zinc granules and place them in a 500 mL flask.
• Step 2: With the help of a thistle funnel, add dilute hydrochloric acid to the zinc granules. If hydrochloric acid isn’t available, dilute sulphuric acid can be used as an alternative.
• Step 3: Hydrogen gas will be automatically collected with the help of a delivery tube via the downward displacement of water. This can be explained by the fact that hydrogen gas is lighter than water.

The setup for the laboratory preparation of hydrogen gas is illustrated below.

The chemical reactions that take place during the preparation of hydrogen gas via this method are listed below.

• General Format: Metal + Dilute Acid → Salt of Metal & Acid + Hydrogen
• With Hydrochloric Acid: Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)
• With Sulphuric Acid: Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

Finally, the hydrogen gas can be collected by the downward displacement of water.

Precautions to be Taken While Preparing Hydrogen Gas in the Laboratory

Before collecting the hydrogen gas with the help of the apparatus, precautions must be taken in order to ensure that all the air inside the apparatus has been displaced. This is because hydrogen gas reacts explosively with air.

Characteristics and Uses of Hydrogen Gas

Hydrogen gas is a colourless gas which does not have any distinct odour. This gas is sparingly soluble in water. The solubility of this gas in water is not affected too much by any changes in temperature. Some uses of hydrogen gas are listed below.

• This gas is used to fill many balloons and airships.
• It is also used for the hardening of animal oils and certain vegetable oils.
• Hydrogen gas is widely used as a fuel in oxy-hydrogen blow pipes.

Frequently Asked Questions – FAQs

How is hydrogen prepared in the laboratory?

Hydrogen can be prepared in the laboratory by the action of hydrochloric acid or sulphuric acid on zinc granules.

Why is hydrogen used to fill balloons?

Hydrogen is lighter than air because of which it will float upwards. So hydrogen is used in balloons.

Does hydrogen cause an explosion?

Hydrogen is lighter than air. Unless ignited, hydrogen does not react with air. If ignited, hydrogen will cause an explosion in the air resulting in the formation of water.

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