Page 36 - NCERT Science Class 10 English Medium
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Bleaching powder is used –
(i) for bleaching cotton and linen in the textile industry, for bleaching
wood pulp in paper factories and for bleaching washed clothes
in laundry;
(ii) as an oxidising agent in many chemical industries; and
(iii) to make drinking water free from germs.
Baking soda
The baking soda is commonly used in the kitchen for making tasty crispy
pakoras, etc. Sometimes it is added for faster cooking. The chemical
name of the compound is sodium hydrogencarbonate (NaHCO ). It is
3
produced using sodium chloride as one of the raw materials.
NaCl + H O + CO + NH → NH Cl + NaHCO
2 2 3 4 3
(Ammonium (Sodium
chloride) hydrogencarbonate)
Did you check the pH of sodium hydrogencarbonate in Activity 2.14?
Can you correlate why it can be used to neutralise an acid? It is a mild
non-corrosive basic salt. The following reaction takes place when it is
heated during cooking –
Heat
2NaHCO Na CO + H O+CO 2
→
3
2
2
3
(Sodium (Sodium
hydrogencarbonate) carbonate)
Sodium hydrogencarbonate has got various uses in the household.
Uses of Baking soda
(i) For making baking powder, which is a mixture of baking soda
(sodium hydrogencarbonate) and a mild edible acid such as
tartaric acid. When baking powder is heated or mixed in water,
the following reaction takes place –
+
NaHCO + H → CO + H O + Sodium salt of acid
3 2 2
(From any acid)
Carbon dioxide produced during the reaction can cause bread or
cake to rise making them soft and spongy.
(ii) Sodium hydrogencarbonate is also an ingredient in antacids.
Being alkaline, it neutralises excess acid in the stomach and
provides relief.
(iii) It is also used in soda-acid fire extinguishers.
Washing soda
Another chemical that can be obtained from sodium chloride is
Na CO .10H O (washing soda). You have seen above that sodium
2 3 2
carbonate can be obtained by heating baking soda; recrystallisation of
sodium carbonate gives washing soda. It is also a basic salt.
Na CO + 10 H O→ Na CO 10. H O
2 3 2 2 3 2
( Sodium
carbonate)
Acids, Bases and Salts 31
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