Question

Describe an example showing evalution of gas in a chemical reaction. Also write the chemical equation​

Answer 1

1.Evolution of gas:

The chemical reaction between zinc and dilute sulphuric acid is characterized by the evolution of hydrogen gas.

Zn(s)+H

2

SO4(aq)→ZnSO

4

(aq)+H

2

(g)

2.Change in colour:

The reaction between the lead nitrate solution and potassium iodide solution.

Pb(NO

3

)

2

(aq)+2KI→PbI

2

(s)+2KNO

3

(aq)

In this reaction colour changes from colourless to yellow.

3.Formation of precipitate:

The action of Barium Chloride on sodium sulphate.

BaCl

2

(aq)+Na

2

SO

4

(aq)→BaSO

4

(s)+2KNaCl(aq)

4.Change in temperature:

The action of dilute sulphuric acid on zinc:

Zn(s)+H

2

SO

4

(aq)→ZnSO

4

(s)+H

2

(g)

In this reaction, heat is evolved.

5.Change in the state:

When the wax is burnt in the form of the wax candle then water and carbon dioxide are formed. Wax is solid, water is a liquid whereas carbon dioxide is a gas.

Answer 2

2HCl (aq) + Zn(s) → ZnCl2 (aq) + H2 (g)

Here, hydrochloric acid oxidizes zinc to produce an aqueous metal salt and hydrogen gas bubbles. Recall that oxidation refers to a loss of electrons, and reduction refers to the gain of electrons. In the above redox reaction, neutral zinc is oxidized to Zn2+, and the acid, H+, is reduced to H2(g). The oxidation of metals by strong acids is another common example of a gas evolution reaction.