Page 26 - NCERT Science Class 10 English Medium

On passing excess carbon dioxide the following reaction takes place:
(
CaCO s)+ H O(l)+ CO (g) → Ca(HCO ) ( aq)
3 2 2 3 2
(Soluble in water)
Limestone, chalk and marble are different forms of calcium carbonate.
All metal carbonates and hydrogencarbonates react with acids to give a
corresponding salt, carbon dioxide and water.
Thus, the reaction can be summarised as –
Metal carbonate/Metal hydrogencarbonate + Acid → Salt + Carbon dioxide + Water

2.1.4 How do Acids and Bases React with each other?

Activity 2.6
Activity 2.6
Activity
Activity 2.6
Activity 2.62.6
n Take about 2 mL of dilute NaOH solution in a test tube and add
two drops of phenolphthalein solution.
n What is the colour of the solution?
n Add dilute HCl solution to the above solution drop by drop.
n Is there any colour change for the reaction mixture?
n Why did the colour of phenolphthalein change after the addition
of an acid?
n Now add a few drops of NaOH to the above mixture.
n Does the pink colour of phenolphthalein reappear?
n Why do you think this has happened?

In the above Activity, we have observed that the effect of a base is
nullified by an acid and vice-versa. The reaction taking place is written as –
NaOH(aq) + HCl(aq) → NaCl(aq) + H O(l)
2
The reaction between an acid and a base to give a salt and water is
known as a neutralisation reaction. In general, a neutralisation reaction
can be written as –
Base + Acid → Salt + Water

2.1.5 Reaction of Metallic Oxides with Acids

Activity
Activity
2.7
Activity 2.7
Activity 2.7
Activity 2.72.7
n Take a small amount of copper oxide in a beaker and add dilute
hydrochloric acid slowly while stirring.
n Note the colour of the solution. What has happened to the copper
oxide?
You will notice that the colour of the solution becomes blue-green
and the copper oxide dissolves. The blue-green colour of the solution is
due to the formation of copper(II) chloride in the reaction. The general
reaction between a metal oxide and an acid can be written as –
Metal oxide + Acid → Salt + Water

Acids, Bases and Salts 21

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