Acids, Bases and Salts CBSE Class 7 Important Question and Answers

Acids, Bases and Salts
1.Name the following:
(i) Substances which furnish hydronium ion in solution.
Ans. Acids
(ii) Substances which turn blue litmus solution red.
Ans.Acids

(iii) Substances which furnish hydroxyl ion in solution.
Ans.Bases
(iv) Substances which turn turmeric paper red.
Ans.Bases
(v) Chemical name for salt which we consume everyday.
Ans.Sodium Chloride
(vi) Base used as foaming agent in fire extinguisher.
Ans.Sodium Hydrogen Carbonate
(vii) A commonly used antacid.
Ans.Baking Soda
(viii) The substances on which litmus solution has no effect.
Ans.Neutrals
(ix) The colour of turmeric solution in soap solution.
Ans.Red
(x) Examples of any two mineral acids and organic acids.
Ans. Mineral Acids: a)Hydrochloric Acid b).Nitric Acid
Organic Acids: a)Acetic Acid b)Citric Acid
(xi) Write the name and colour of two salts found in the laboratory.
Ans.Copper sulphate(blue)
ferous Sulphate

Ans. Across 
2.Sodium Hydroxide
4.turmeric
5.Antacid
6.Litmus
9.Alkali
10.Universal
12.Formic

Down
1.Neutralization
3.Indicators
7.Base
8.Sour
11.Salt

Q.4. Fill in the blanks –
(i) The new substance formed when an acid reacts with a base is ___________.Salt
(ii) Heat is Evolved___________ during a neutralization reaction.
(iii) When dilute sulphuric acid is added to lime water, the reaction mixture becomes Neutralize
(iv) HCl___________acid is present in our stomach.
(v) Milk of magnesia contains a base called ___________.Magnesium Hydroxide
(vi) Calamine lotion contains ___________.Zinc Carbonate


Q.5 Name the acids present in the following –
(i) Curd: :Lactic Acid (ii) Spinach:Oxalic (iii) Tamarind:Tartaric Acid
(iv) Amla:Ascorbic Acid (v) Aerated drinks:Carbonic Acid (vi) Vinegar:Acetic Acid
(vii)Apple:Malic Acid
Q.6. Name the bases present in the following –
(i) Lime water:Calcium Hydroxide (ii) Soap:Sodium Hydroxide (iii) Milk of magnesia:Magnesium Hydroxide
(iv) Slaked lime:Sodium Hydrogen Carbonate (v) Caustic soda:Sodium Hydroxide (vi) Caustic potash:Potassium Hydroxide
Q.7. Give the natural source of the following acids:
(i) Citric acid:Citrus fruits such
as oranges,
lemons, etc.
(ii) Lactic acid:Curd
(iii) Acetic acid:Vinegar
(iv) Tartaric acid:Tamarind,grapes,unripe mangoes
(v) Oxalic acid:spinach
(vi) Maleic acid:apple
Q.8. What are the colour changes of the following indicators:–
(a) in acidic medium
(b) in basic medium
(c) in neutral medium

(i) China rose (ii) Red litmus (iii) Methyl orange
(iv) Phenolphthalein (v) Turmeric powder (vi) Blue litmus

Q.9. Choose the correct alternatives –
(i) The colour of methyl orange in acids is –
(a) yellow (b) pink (c) red (d) orange
Ans.Orange

(ii) Acidic soil can be neutralized by adding –
(a) quicklime (b) vinegar (c) nitric acid (d) formic acid
Ans.Quicklime

(iii) Atul was given a colourless solution in a test tube. He put a drop of this solution on blue litmus paper. It remained blue in colour. The colourless solution is
(a) acidic in nature
(b) basic in nature
(c) neutral in nature
(d) nothing can be said
Ans.Nothing can be said

(iv) A solution turns red litmus paper blue. If a drop of phenolphthalein is added to it,
(a) it turns pink
(b) it turns red again
(c) it remains colourless
(d) it turns blue
Ans.It turns pink

(v) Orange juice is sour in taste due to the presence of
(a) acetic acid
(b) citric acid
(c) formic acid
(d) tartaric acid
Ans.Citric Acid



Answer the following questions:
(i) Where do we get litmus solution from?
Ans.The most commonly used natural indicator is litmus. It is extracted
from lichens (Fig. 5.1). It has a mauve (purple) colour in distilled water.It is available in the form of a
solution, or in the form of strips of
paper, known as litmus paper.
(ii) Give any two use of acids?
Ans.a.Used in making batteries
b.Used in making explosives
(iii) What causes indigestion? How it can be treated?
Ans.Overeating results in indigestion as gastric glands secrete too much HCL Acid.It can be treated by taking antacid tablet which are basic in nature and neutralize the effect of HCL

(iv) How can you neutralize the effect of ant sting?
Ans.Ant Sting contains formic Acid and its effect can be neutralized by applying calamine solution which is basic in nature and neutralize the effect of formic acid
(v) What makes the soil acidic? How it can be treated?
Ans.Excessive use of fertlizers often ends up making soil acidic.It can be treated by adding slaked lime to the soil.
(vi) Mention any two uses of bases.
(vii) Is the distilled water acidic/ basic/ neutral? How would you verify it?
Ans.Distilled Water is Neutral.There will be no change in the blue or red color litmus paper in distilled water
and Distilled water will not conduct electricity

viii) Describe the process of neutralization with the help of an example.
Ans.When Acid and Base react with each other they neutralize the effect of each other, in this reaction salt and water are formed and heat energy is released
for e.g
Sodium Hydroxide + Hydrochloric Acid----------------------->Sodium Chloride +Water
(ix) Dorji has a few bottles of soft drink in his restaurant. But unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?
Ans.Dorji can use litmus paper to identify which bottle is which .liquid in the bottle which turns red litmus blue is basic in nature, and the one that changes blue litmus to red is acidic and the one which has no effect of blue or red litmus paper is neutral
(x) Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric indicator.


Ans.Turmeric will become faded yellow in acid
Turmeric will turn red in Sodium hydroxide
and there will be no change in sugar solution
(xi) Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain

Ans.The solution can be either basic or neutral.

Q.2. Define the following with examples:
(i) Indicators:a compound which changes colour at a specific pH value or in the presence of a particular substance, and can be used to monitor acidity, alkalinity,
(iii) Natural indicators:Indicators which are derived from organic matter are known as natural indicators for e.g litmus paper, turmeric


Differentiate between:
(i) Acids and bases



Ans.Acids:
They are sour in taste
They turn blue litmus red
They release H+ Ions in aqueous solution
Bases:
They are bitter in taste and soapy to touch
They turn blue litmus red
They release OH- ions in aqueous solution
(ii) A base and an alkali
Alkali is a sub group of Base all bases which are soluble in water are called alkali and
(iii) Mineral acids and Organic acids
Mineral Acids
Acids are are derived from chemicals are mineral acids
They are corrosive in nature
They completely release H+ ions in aqueous solution
for e.g Hydrochloric acid,Nitric acid
Organic Acids
They are derived from plants and animals
They are non corrosive
They partially release H+ ions in aqueous solution
(iv) Concentrated acids and Dilute acids
Ans.acids which contain high concentration of water are dilute acids and acids which contain less percentage of acids are concentrated acids