Ncert Exemplar Solutions Class 7 Science Acids Bases and Salts

Welcome to NCTB Solutions. Here with this post we are going to help 7th class students for the Solutions of NCERT Exemplar Class 7 Science Book, Unit 5, Acids, Bases and Salts. Here students can easily find step by step solutions of all the problems for Acids, Bases and Salts, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.

Acids, Bases and Salts all Question Solutions :

Multiple Choice Questions :

Question no – (1)

The correct way of making a solution of acid in water is to

Answer :

The correct answer is option – (b)

The correct way of making a solution of acid in water is to add acid to water.

Question no – (2)

Products of a neutralisation reaction are always

Answer :

The appropriate option is – (c)

Products of a neutralisation reaction are always a salt and water.

Question no – (3)

Turmeric is a natural indicator. On adding its paste to acid and base separately, which colours would be observed

Answer :

The correct answer is option – (b)

Yellow in acid and red in base.

Question no – (4)

Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions, respectively are

Answer :

The correct answer is alternative – (d)

Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions, respectively are colourless and pink.

Question no – (5)

When the soil is too basic, plants do not grow well in it. To improve its quality what must be added to the soil?

Answer :

The correct answer is option – (a)

Organic matter must be added to the soil.

Question no – (6)

‘Litmus’, a natural dye is an extract of which of the following?

Answer :

The appropriate option is – (c)

‘Litmus’, a natural dye is an extract of Lichen.

Question no – (7)

Neutralisation reaction is a

Answer :

The correct answer is option – (d)

Neutralisation reaction is a chemical change that cannot be reversed.

Question no – (8)

A solution changes the colour of turmeric indicator from yellow to red. The solution is

Answer :

Alternative – (a) is the correct answer.

The solution is basic.

Question no – (9)

Which of the following set of substances contain acids?

Answer :

The correct answer is option – (d)

Curd, vinegar contain acids.

Question no – (10)

On adding phenolphthalein indicator to a colourless solution, no change is observed. What is the nature of this solution?

Answer :

The appropriate option is – (c)

The nature of this solution will be Either acidic or neutral.

Question no – (11)

Which of the following is an acid-base indicator?

Answer :

The correct answer is option – (c)

Turmeric is an acid-base indicator.

Very Short Answer Questions :

Question no – (12)

Answer :

There is a simple way to get solid sodium chloride out of this solution and that is to evaporate the water from the solution till the sodium chloride is left behind in the container.

Question no – (13)

Answer :

(a) All substances are either acidic or basic

This statement is False.

Because, Not all substances are either acidic or basic, some can be neutral too.

(b) A compound if acidic will turn all indicators red

This statement is False.

Because, A compound if acidic turns only blue litmus to red.

(c) Lime water turns red litmus blue

This statement is True.

(d) Common salt dissolved in water turns blue litmus red –

This statement is False.

Because, Common salts dissolved in water does not turns blue litmus red.

(e) Phenolphthalein is a natural indicator

This statement is False.

Reason : Phenolphthalein is a man made indicator.

(f) Calamine can be used to treat ant’s sting

This statement is True.

(g) Lemon water is basic in nature

This statement is False.

Reason : Lemon water is acidic in nature.

Question no – (14)

Answer :

Paheli should not be given orange because it is acidic in nature so it will increase the acidity level and worsen the situation.

Short Answer Questions :

Question no – (15)

Answer :

Test Tube – (A)

Nature of Solutions – Neutral.

Change in colour of red litmus – No change at all.

Test Tube – (B)

Nature of Solutions – Basic.

Change in colour of red litmus – Turns to blue.

Test Tube – (C)

Nature of Solutions – Acidic.

Change in colour of red litmus – No change at all.

Test Tube – (D)

Nature of Solutions – Neutral.

Change in colour of red litmus – No change at all.

Question no – (16)

Answer :

The child by stung by a wasp which injected a acidic liquid in him. So in order to relief the child of the pain we must apply the moist baking on the infected area as it is basic in nature so it will neutralize the acid.

Question no – (17)

Answer :

The effect of an ant bite is neutralized by rubbing moist baking soda.

Question no – (18)

Answer :

(a) → (iii) Unripe mangoes.

(b) → (v) Lime water.

(c) → (iv) Ant’s sting.

(d) → (i) Soap.

(e) → (ii) Curd.

Question no – (19)

Answer :

(a) Lemon juice and vinegar taste Sour because they contain Acids.

(b) Turmeric and litmus are Natural acid-base indicators.

(c) Phenolphthalein gives Pink colour with lime water.

(d) When an acidic solution is mixed with a basic solution, they neutralise each other forming salt and water.

Long Answer Questions :

Question no – (20)

Answer :

China rose is a natural indicator so when the solution A was added it turned pink as the solution was acidic in nature, just like that when solution B was added to it turned green and since no colour change was observed when solution C was added it means that it was neutral in nature.

Question no – (22)

Answer :

If the farmer finds out the soil is acidic he must treat the soil by adding bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide) which neutralizes the soil. But if the soil is too basic organic matter like compost should be added as it releases acids which neutralizes the acidity of the soil.

Question no – (23)

Answer :

In order to the nature of the solution we can taste the solutions, so if the solutions taste sour it will be basic or if it taste bitter then it’s basic but if it’s taste other than sour or basic then it’s neutral. The tamarind solution taste sour so it’s acidic. The baking soda solution taste bitter so it’s basic. While the sugar and salt solutions taste sweet and salty so they are neutral in nature.

Question no – (24)

Answer :

(a) a piece of blue litmus paper in each test tube.

= When blue litmus paper is added to solution A it turns red, but it remains blue in solution B and C.

(b) a piece of red litmus paper in each test tube.

= When red litmus is added to solution A and C it remains red ,but in solution B it changes to blue.

(c) a few drops of phenolphthalein solution to each test tube.

= When phenolphthalein drops are added to solution A and C no colour changes are observed while solution B changes to pink.

Question no – (25)

Answer :

(a) The water is contaminated by the acidic or basic waste which is released by the factory in the water. This makes the water inhabitable for the fishes and eventually kills them.

(b) If the factory waste is acidic in nature it’s harmful effects can be neutralized by adding basic substances such as quick lime or slaked lime.

Question no – (26)

Answer :

The two neutralization effects related to daily life situations are,

• Indigestion : When our stomach has too much acids it causes indigestion which if often treated by antacid such as milk of magnesia which neutralizes the acid.

• Ant bite : When a person is stung by a bee, it releases an acid in the person. The effects of the acid can be neutralized by rubbing moist baking soda or calamine solution over the infected area.

Other Chapter Solutions :

👉 Nutrition in Plants

👉 Nutrition in Animals

👉 Fibre to Fabric

👉 Heat

👉 Physical and Chemical Changes

👉 Weather, Climate and Adaptation of Animals to Climate

👉 Wind, Storm and Cyclone

👉 Soil

👉 Respiration in Organisms

👉 Transportation in Animals and Plants

👉 Reproduction in Plants