CBSE Class 10 Science 2019 · Paper 31/1/3 · Question 21

Acids, Bases and Salts 5 marks Medium

Write the main difference between an acid and a base. With the help of suitable examples explain the term neutralization and the formation of -

(i)acidic,
(ii)basic and
(iii)neutral salts.

Answer

An acid gives $H^{+}$ and a base gives $OH^{-}$ ; neutralization gives salt and water; examples: $NH_{4} Cl$ acidic, $Na_{2} CO_{3}$ basic, $KNO_{3}$ neutral.

Main difference: An acid gives hydrogen ions,

H^{+} (a q)

, in aqueous solution, whereas a base gives hydroxide ions,

OH^{-} (a q)

. Neutralization: The reaction of an acid with a base to form a salt and water is called neutralization; the

H^{+}

ions of the acid combine with the

OH^{-}

ions of the base to form water. Example:

NaOH (a q) + HCl (a q) ⟶ NaCl (a q) + H_{2} O (l)

(i) Acidic salt (strong acid + weak base; solution pH below 7):

NH_{4} OH + HCl ⟶ NH_{4} Cl + H_{2} O

(ii) Basic salt (weak acid + strong base; solution pH above 7):

2 NaOH + H_{2} CO_{3} ⟶ Na_{2} CO_{3} + 2 H_{2} O

(iii) Neutral salt (strong acid + strong base; solution pH 7):

KOH + HNO_{3} ⟶ KNO_{3} + H_{2} O

Any other correct examples earn credit.

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CBSE Class 10 Science 2019 · Paper 31/1/3 · Question 21

Answer

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