ADDITIONAL QUESTIONS AND ANSWERS

1) What is meant by acids? Give two properties of acids?
Ans: Acids are those chemicals which produce hydrogen ions in its aqueous solution
eg: Citric acid, Sulphuric acid, Hydrochloric acid, etc.
Properties of acids are:
(i) It has sour taste.
(ii) It turns blue litmus into red.

2) What is meant by bases? Give two properties of bases?
Ans: Bases are those chemicals which produce hydroxide ions (OH-) in its aqueous solution e.g. Sodium hydroxide, Calcium hydroxide, Magnesium hydroxide etc.
Properties of bases are:
(i) Base is bitter in taste.
(ii) Base converts red litmus into blue.

3) Describe the preparation of litmus solution and state any use.
Ans: Litmus solution is a purple dye which is extracted from a plant lichen. This dye is used an indicator to tests for acids and bases.

4) What are Indicators? Name the types.
Ans: Indicators are those substances which indicates that whether the given chemical is an acid or a base.
The types of indicators are
(i) Olfactory indicators     (ii) Synthetic indicators     (iii) Natural indicators

5) What happens when an acid reacts with a base?
Ans: When an acid reacts with a base then it produces salt and water and it is known as neutralization reaction.
Eg:  a) NaOH  +  HCl  →  NaCl  +  H2O
b)Mg (OH)2  +  H2SO4  → MgSO +  2H2O

6) What happens when an acid reacts with a metal?
Ans: When an acid reacts with a metal it produces metal salt and hydrogen gas.
Eg:    Mg + 2 HCl  →  MgCl +  H2
          2 Na + 2 HCl  →  2 NaCl  + H2

7) What happens when an acid reacts with metal carbonate?
Ans: When an acid reacts with metal carbonate then it produces metal salt, carbon dioxide
and water.
Eg:   Na2CO3 + HCl  →  2NaCl  +  CO2 +  H2O
CaCO3 + HCl  →  CaCl2 +  CO2  +  H2O

8) Give some examples of metal oxide with acid?
Ans: (i) Na2O  +  HCl  →  NaCl  +  H2O
(ii) CaO  +  HCl  →  CaCl2  +  H2O

9) What do all acids have in common and classify accordingly?
Ans: All acids have hydrogen ions (H+) in common in their aqueous form.The types of acids are
Concentrated acid: Concentrated acids are those which contain less amount of water.
Dilute acid: Dilute acid are those which contain more amount of water.

10) How are bases different from alkalis?
Ans: Bases which are soluble in water and produce OH- are called alkalis. Some examples are:
a) Sodium hydroxide ( NaOH )   → Na+ +  OH- .
b) Potassium hydroxide ( KOH )  → K+  + OH-.
All alkalis are bases but all base are not alkalis.
Eg: Cu (OH)2 is a base but not a alkali.

11) Name the acids which are present in the following which attribute a sour taste to them:
Lemon Juice, Vinegar, Tamarind, and Sour Milk

Ans: Lemon juice contains citric acid.
Vinegar contain acetic acid.

Tamarind contains tartaric acid.
Sour milk contains lactic acid