Chapter 5 Acids, Bases and Salts Solutions

Maharashtra State Board Class 9 Science Solutions Chapter 5 Acids, Bases and Salts

Class 9 Science Chapter 5 Acids, Bases and Salts Textbook Questions and Answers

1. Identify the odd one out and justify.

(a) Chloride, nitrate, hydride, ammonium
Answer:
Ammonium is the odd one out as it is a basic radical and rest all are acidic radicals. Generally, basic radicals are formed by the removal of electrons from the atom of metals such as Na⁺, Cu²⁺. But there are some exceptions, such as NH₄⁺.

(b) Hydrogen chloride, sodium hydroxide, calcium oxide, ammonia
Answer:
Hydrogen chloride is the odd one out. It is acidic and rest all are basic.

(c) Acetic acid, carbonic acid, hydrochloric acid, nitric acid
Answer:
Carbonic acid is the odd one out. It is a dibasic acid and rest are all monobasic acids.

(d) Ammonium chloride, sodium chloride, potassium nitrate, sodium sulphate
Answer:
Ammonium chloride is the odd one out, as it is made up of a strong acid and weak base and rest all are formed from strong acid and strong base.

(e) Sodium nitrate, sodium carbonate, sodium sulphate, sodium chloride
Answer:
Sodium carbonate is the odd one out, as it is made up of a weak acid and strong base, and rest all are formed from strong acid and strong base.

(f) Calcium oxide, magnesium oxide, zinc oxide, sodium oxide.
Answer:
Zinc oxide is the odd one out, as it is an amphoteric oxide, and rest all are basic oxides.

(g) Crystalline blue vitriol, crystalline common salt, crystalline ferrous sulphate, crystalline sodium carbonate.
Answer:
Crystalline common salt is the odd one out, as it does not contain water of crystallisation. It is an ionic compound and ionic compounds are crystalline in nature and rest all have their crystalline structure because of their water of crystallization.

(h) Sodium chloride, potassium hydroxide, acetic acid, sodium acetate.
Answer:
Acetic acid is the odd one out. It is an acid, the rest are all salts.

2. Write down the changes that will be seen in each instance and explain the reason behind it.

(a) 50ml water is added to 50ml solution of copper sulphate.

Answer:

(b) Two drops of the indicator phenolphthalein were added to 10ml solution of sodium hydroxide.

Answer:

(c) Two or three filings of copper were added to 10ml dilute nitric acid and stirred.
Answer:
When copper metal reacts with dilute nitric acid, the metal does not displace hydrogen from the acid like reaction with other metals. Instead the reaction produces nitric oxide, (NO).

(d) A litmus paper was dropped into 2ml dilute HCl. Then 2ml concentrated NaOH was added to it and stirred.
Answer:
Blue litmus Paper:

Red litmus paper:

(e) Magnesium oxide was added to dilute HCl and magnesium oxide was a added to dilute NaOH.
Answer:
(i) Magnesium oxide + dil HCl.
This is a neutralization reaction. Magnesium oxide is an insoluble base, it reacts with dilute HCl to produce a soluble salt MgCl₂and water H₂O.

(ii) Magnesium oxide + NaOH.
No chemical reaction takes place between magnesium oxide and sodium hydroxide.

(f) Zinc oxide was added to dilute HCl and zinc oxide was added to dilute NaOH.
Answer:

(g) Dilute HCl was added to limestone.
Answer:

(h) Pieces of blue vitriol were heated in a test tube. On cooling, water was added to it.
Answer:

(i) Dilute H₂SO₄was taken in an electrolytic cell and electric current was passed through it.
Answer:

[H+ ions gains electrons and are converted to hydrogen gas]

Cathode reaction:

Anode reaction:

3. Classify the following oxides into three types and name the types.
CaO, MgO, CO₂, SO₃, Na₂O, ZnO, Al₂O₃, Fe₂O₃Answer:
There are three types of oxides : Basic oxides, Acidic oxides and Amphoteric oxides.

Generally metal oxides are basic in nature.
Exception : Al₂O₃and ZnO are amphoteric oxides.
Generally non-metal oxides are acidic in nature.

4. Explain by drawing a figure of the electronic configuration.

a. Formation of sodium chloride from sodium and chlorine.
Answer:

b. Formation of a magnesium chloride from magnesium and chlorine.
Answer:

5. Show the dissociation of the following compounds on dissolving in water, with the help of chemical equation and write whether the proportion of dissociation is small or large.
Hydrochloric acid, Sodium chloride, Potassium hydroxide, Ammonia, Acetic acid, Magnesium chloride, Copper sulphate.
Answer:
(a) Hydrochloric acid (HCl)

(b) Sodium chloride (NaC1)

(c) Potassium hydroxide (KOH)

(d) Ammonia (NH₃)
(i)
(ii) Ammonia dissolves in water to form NH₄OH (ammonium hydroxide). NH₄OH does not dissociate completely as it is a weak base. The aqueous solution contains a small proportion of OH^–ions and the concerned basic radical along with a large proportion of undissociated molecules of the base i.e. NH₄OH.
(iii) The proportion of dissociation is small.

(e) Acetic acid (CH₃COOH)

(f) Magnesium chloride (MgCl₂)

(g) Copper sulphate (CuSO₄)

6. Write down the concentration of each of the following solutions in g/L and mol/L.

a. 7.3g HCl in 100ml solution
b. 2g NaOH in 50ml solution
c. 3g CH₃COOH in 100ml solution
d. 4.9g H₂SO₄in 200ml solution
Answer:
To find : The concentration in g/L.
Solution:

7. Obtain a sample of rainwater. Add to it a few drops of universal indicator. Meausre its pH. Describe the nature of the sample of rainwater and explain the effect if it has on the living world.
Answer:

8. Answer the following questions.

a. Classify the acids according to their basicity and give one example of each type.
Answer:

b. What is meant by neutralization? Give two examples from everyday life of the neutralization reaction.
Answer:

Examples in daily life:

c. Explain what is meant by electrolysis of water. Write the electrode reactions and explain them.
Answer:
Electrolysis of water:

9. Give a reason for the following.

a. Hydronium ions are always in the form H₃O⁺.
Answer:

b. Buttermilk spoils if kept in a copper or brass container.
Answer:

10. Write the chemical equations for the following activities.

(a) NaOH solution was added to HCl solution.
Answer:
When NaOH reacts with HCl, it gives NaCl and water.

(b) Zinc dust was added to dilute H₂SO₄.
Answer:
When zinc reacts with dilute sulphuric acid, it forms zinc sulphate and hydrogen gas is liberted.

(c) Dilute nitric acid was added to calcium oxide.
Answer:
When dilute nitric acid reacts with calcium oxide, it forms calcium nitrate and water.

(e) Carbon dioxide gas was passed through KOH solution.

(f) Dilute HCl was poured on baking soda.

11. State the differences.

a. Acids and bases
Answer:

b. Cation and anion
Answer:

c. the Negative electrode and the positive electrode.

Answer:

12. Classify aqueous solutions of the following substances according to their pH into three groups : 7, more than 7, less than 7.

Common salt, sodium acetate, hydrochloric acid, carbon dioxide, potassium bromide, calcium hydroxide, ammonium chloride, vinegar, sodium carbonate, ammonia, sulphur dioxide.
Answer:

Class 9 Science Chapter 5 Acids, Bases and Salts Intext Questions and Answers

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