Solution to Activity 2.4 of NCERT Class 10 Science Chapter 2 Acids, Bases and Salts

4. Complete Activity 2.4 (Page 20).

Place a few pieces of granulated zinc metal in a test tube.
Add 2 mL of sodium hydroxide solution and warm the contents of the test tube.
Repeat the rest of the steps as in Activity 2.3 and record your observations.

Answer:

Aim: To carry out the reaction between Zinc and NaOH and conclude based on the observations.

Materials Required: Granulated zinc metal, sodium hydroxide, test tube.

Procedure:

(i) Set up the apparatus as shown in the figure. Attached the test tube to the laboratory stand. Put the cork on the mouth of the test tube and place the delivery tube through the cork as shown. Now submerge the other end of the delivery tube in the soap solution as shown.

(i) Open the cork and place a few pieces of the granulated zinc metal in the test tube.

(ii) Now add 2 mL of sodium hydroxide and close the mouth of the test tube with the cork.

(iii) Warm the contents of the test tube using a Bunsen burner.

(iv) Note what happens on the surface of zinc granules.

(v) Observe what happens in the soap solution.

(vi)Hold the burning candle near a gas filled bubble above the soap solution as shown in the figure and note the observations.

Observations:

Gas bubbles are observed on the surface of zinc granules.
Bubbles form in the soap solution and rise up into the air.
The bubbles burn with a popping sound when the candle is brought next to them.

Conclusions:

The bubbles on the surface of zinc granules and the popping sound indicate that hydrogen gas was evolved in the reaction.
Sodium hydroxide reacted with zinc metal to form sodium zincate and hydrogen gas. The reaction is shown below:
2NaOH(aq) + Zn(s) —> Na₂ZnO₂(s) + H₂(g)

“4. Complete Activity 2.4 (Page 20).

Repeat the rest of the steps as in Activity 2.3 and record your observations.

Place a few pieces of granulated zinc metal in a test tube.

Add 2 mL of sodium hydroxide solution and warm the contents of the test tube.” Solved