How do Acids and Bases React with Metals?

Activity 2.3

CAUTION: This activity needs the teacher’s assistance.

1. Set the apparatus as shown in Fig. 2.1.
2. Take about 5 mL of dilute sulphuric acid in a test tube and add a few pieces of zinc granules to it.
3. What do you observe on the surface of zinc granules?
4. Pass the gas being evolved through the soap solution.
5. Why are bubbles formed in the soap solution?
6. Take a burning candle near a gas filled bubble.
7. What do you observe?
8. Repeat this Activity with some more acids like HCl, HNO₃ and CH₃COOH.
9. Are the observations in all the cases the same or different?

Note that the metal in the above reactions displaces hydrogen from the acids. This is seen as hydrogen gas. The metal combines with the remaining part of the acid and forms a compound called a salt. Thus, the reaction of a metal with an acid can be summarised as –

Acid + Metal → Salt + Hydrogen gas

Can you now write the equations for the reactions you have observed?

Activity 2.4

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

The reaction that takes place can be written as follows.

You find again that hydrogen is formed in the reaction. However, such reactions are not possible with all metals.