RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Rajasthan Board RBSE Class 7 Science Chapter 5 Acids, Bases and Salts

RBSE Solutions for Class 7 Science

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

RBSE Class 7 Science Acids, Bases and Salts Intext Questions and Answers

Page No 46.

Question 1.
Compile the taste of following food products in a table.
Answer:
Table : Food products according to their taste
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-1

Page No 47.

Question 2.
Why Lemon and orange Juice, Amla, tamarind etc. sour in taste ?
Answer:
These food materials are sour in taste because all of these contains acids and acids are sour in taste. Hence sour in taste.

Question 3.
What are acids ?
Answer:
Acid is an English term. Acid word comes from a latin word Acidus. which means sour. So we can say that the substances that are sour in taste arc acids.

Question 4.
What reaction occurs when Lemon Juice is mixed in baking soda ?
Answer:
When we mix some lemon Juice in solution of baking soda, we observe some bubbles in the glass and also a gas releases in this reaction.

Question 5.
Why matchstick blows out when we bring it near the glass containing mixture of baking soda solution and lemon juice ?
Answer:
Acid on reaction with baking soda (Sodium Bicarbonate). forms CO. gas which blows out the matchstick.

Page No 49.

Question 6.
How does baking soda taste ? And what do you feel on touching it?
Answer:
Baking soda is bitter in taste and soapy in touch.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Page No 50.

Question 7.
Is it possible to identify the nature of substances by their taste ?
Answer:
No. because it can be dangerous to touch or taste the unknown substances. To identify the nature of substance whether it is acidic or basic without touching or tasting. We use some special substances that are called indicators so indicators tell the nature of substances by changing its colour.

Page No 51.

Question 8.
What happens when adding few drops of lime water on turmeric paper?
Answer:
The yellow colour turns into red.

Question 9.
Test the following solution given in table and note the observation in table and’ conclude the result.
Answer:
Table : Test of solution from Turmeric paper
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-2

RBSE Class 7 Science Acids, Bases and Salts Text Book Questions and Answers

Choose the correct option:

Question 1.
Acid present in tamarind –
(a) Lactic acid
(b) Citric acid
(c) Tartaric acid
(d) Acetic acid
Answer:
(c) Tartaric acid

Question 2.
Choose base from the following compounds –
(a) Salt
(b) Acid of salt
(c) Washing Soda
(d) Malic acid
Answer:
(c) Washing Soda

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 3.
Gas formed by the reaction of acid and Zn-
(a) Hydrogen
(b) Nitrogen
(c) CO2
(d) Oxygen
Answer:
(a) Hydrogen

Question 4.
Which of the following is nitric acid
(a) HNO3
(b) H2SO4
(c) HCl
(d) CH3COOH
Answer:
(a) HNO3

Fill in the blanks:

  1. Bases turn red litmus to ………………………
  2. Reaction of acid with base forms ………………………
  3. Acid reacts sodium bicarbonate and evolves ……………………… gas.
  4. HCl+NaOH → ……………………… + ………………………

Answer:

  1. blue
  2. Salt & water
  3. Carbon dioxide
  4. NaCl + H2O

Match the Column A and Column B –
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-3
Answer:

  1. (c)
  2. (a)
  3. (b)
  4. (e)
  5. (d)

Short Answer Type Questions:

Question 1.
Write the names of any two natural indicators.
Answer:

  1. Litmus
  2. Turmeric

Question 2.
In which reaction do acids and bases react to form salt and water?
Answer:
The reaction in which an appropriate amount of acid and base undergo continuous reaction and form salt and water with the release of heat. is known as neutralization reaction, eg.
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-4

Question 3.
Write three properties of bases.
Answer:

  1. Base s turn red. plant pigments into blue.
  2. These arc bitter in taste.
  3. These are Soapy in touch.

Question 4.
A blue litmus is dipped in a solution. It becomes red. Write the nature of the solution. Explain it.
Answer:
If a blue litmus is dipped in a solution and it turns red, the solution will be acidic in nature because acids turn blue litmus solution into red.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 5.
What is acidity ? Write its treatment.
Answer:
Hydrochloric acid helps in digestion of food in our stomach but hen it is secreted more in amount than requirement, then acidity occurs. For treatment of acidity. we use milk of magnesia (magnisicium Hydroxide) which is a good antacid and it neutratizes the effect of acid secreted.

Question 6.
What happens if waste material of industries is drained off without treatment?
Answer:
Waste material of industries contains acidic substances. If these waste material is drained off directly without treatment in water bodies. then it may harm fishes. aquatic animals and aquatic plants. So these wastes should be treated with basic substances to neutralize their harmful effect so that aquatic life may be protected.

Question 7.
Why do we not use metal container to keep lemon juice ?
Answer:
Lemon Juice should not be kept in metal container because Lemon Juice contains acid. Acid reacts with metals to form harmful substance and it may spoil.

Long Answer Type Questions:

Question 1.
What are indicators ? name any two indicators. Explain the effect of these indicators on acids and bases ?
Answer:
Indicators –
To identify the nature of substance whether it is acidic or basic without touching or tasting. We use some special substances that arc called indicators. So. indicators tell the nature of substance by changing its colour.

Types – Indicators are of to types –
1. Natural indicators – cg. Litmus paper. turmeric, petals of China rose. Etc.

2. Artificial indicators – cg. Phenophthalene. methyl orange. etc. Effect of indicators on acids or bases – Litmus is the most common natural indicator which is used to identify acids and bases. It is present in forms of solution and paper strips. These paper sheets arc known as Litmus papers. Litmus are of two types –

  1. Blue litmus
  2. Red Litmus. Acids turn blue litmus paper into red and bases turn red litmus into blue colour.

Question 2.
Write three differences between acids and bases.
Answer:
Difference between acids and bases –
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-5

Question 3.
Write uses of following –

  1. Washing soda
  2. Sodium chloride
  3. Sulphuric acid
  4. Calcium oxide
  5. Acetic acid.

Answer:
1. Washing Soda –
It is sodium carbonate. Its chemical formula is Na2CO3. It is used in houses for washing clothes and for softening of water in industries.

2. Sodium Chloride –
It is also called table salt. Its chemical formula is NaCl. it is used in houses in food and for making chlorine in industries.

3. Sulphuric acid – The chemical formula of Sulphuric acid is H2SO4. It is used in industries for formation of fertilizers like formation of ammonium sulphate and in batteries, dyes, clothes and paper industries.

3. Calcium Oxide –
it is often called Quick Lime. Its chemical formula is CaO. It is used in houses for white washing and treating wounds and for making ammonia and extraction of iron in industries.

4. Acetic acid –
it is also called vinegar. Its chemical formula is CH3COOH. It is used in making pickets in houses, in making medicines and in making cellulose acetate (Photo film) in industries and in making white lead.

RBSE Class 7 Science Acids, Bases and Salts Important Questions and Answers

Objective Questions:

Question 1.
Substances which are sour in taste are called –
(a) Bases
(b) Acids
(c) Salt
(d) None of these
Answer:
(b) Acids

Question 2.
Which gas is released when acids reacts with metals ?
(a) Carbon dioxide
(b) Hydrogen
(c) Oxygen
(d) All of these
Answer:
(b) Hydrogen

Question 3.
Which is artificial indicator in following –
(a) Petals of china rose
(b) Turmeric
(c) Litmus paper
(d) Phenolphthalene
Answer:
(d) Phenolphthalene

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 4.
Generally salts are –
(a) Acidic
(b) Bases
(c) Neutral
(d) None of these
Answer:
(c) Neutral

Question 5.
Which one is the chemical formula of sodium hydroxide –
(a) HNO3
(b) NaOH
(c) H2SO4
(d) NaCl
Answer:
(b) NaOH

Question 6.
In the following, which substances are neutral in nature –
(a) Salt
(b) Acid
(c) Base
(d) All
Answer:
(a) Salt

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 7.
Gas which is used to blow out flame is –
(a) Oxygen
(b) Nitrogen
(c) Carbon dioxide
(d) Ammona
Answer:
(c) Carbon dioxide

Question 8.
Plant dyes are converted into which colour by bases –
(a) Red
(b) Blue
(c) Blue & Red
(d) Green
Answer:
(b) Blue

Question 9.
Acids convert blue plant dyes into –
(a) Blue
(b) Green
(c) Red
(d) Yellow
Answer:
(c) Red

Fill in the blanks:

  1. Bases converts red plant dyes into ……………………. (Neutral / Blue)
  2. Indicators tells about ……………………. of the substance by changing their colour. (Natural / Shape)
  3. Salt solutions are ……………………. of electricity. (Insulator/ Conductor)
  4. Sodium chloride is also called ……………………. (common salt / Soda)
  5. Litmus is obtained from ……………………. (Fungi / Lichen)

Answer:

  1. Blue
  2. Nature
  3. Conductor
  4. Common salt
  5. Lichen.

Match the Column I with Column II correctly –

Question 1.
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-6
Answer:

  1. (b)
  2. (c)
  3. (e)
  4. (a)
  5. (d)

Very short answer type Questions:

Question 1.
How can we taste food materials?
Answer:
We can taste food materials by taste buds present on our tongue in mouth.

Question 2.
Which gas is released when zinc is reacted with acid solution ?
Answer:
Hydrogen gas is released on reaction between zinc granules and acid solution.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 3.
Which acid is present in Lemon, Orange ?
Answer:
Citric acid is found.

Question 4.
What are the products when acids react with sodium bicarbonate ?
Answer:
Carbon dioxide gas is formed.

Question 5.
Give examples of some sour substances.
Answer:
Vinegar, Lemon, Orange, Amla. Curd, Tamarind, Grapes, etc.

Question 6.
What are neutral solutions?
Answer:
Solutions which do not perform any colour change in litmus test.

Question 7.
Neutral substances are basic or acidic in nature?
Answer:
Neither basic nor acidic. they arc neutral.

Question 8.
Give examples of neutral substances.
Answer:

  1. Salt
  2. Ammonium Chloride
  3. Calcium chloride
  4. Sodium Carbonate etc.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 9.
Give names of some natural indicators.
Answer:

  1. Litmus paper
  2. Turmeric
  3. Petals of china rose.

Question 10.
Which colour appears when phenolphthalein is added in basic solution?
Answer:
Pink colour appears.

Question 11.
Which colour appears when phenolphthalein is added in acidic solution?
Answer:
Solution becomes colourless

Question 12.
What are indicators ?
Answer:
To indentify the nature of substance whether it is acidic or basic without touching or tasting. we use some special substances that arc called indicators.

Question 13.
How indicators tell about the nature of substance ?
Answer:
They tell about the nature of substance by changing their colour.

Question 14.
What are the types of indicators.
Answer:
indicators are of two types –

  1. Natural indicators
  2. Artificial indicators.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 15.
Give an example of equation of neutralization reaction.
Answer:
Salt and water is obtained b reaction between acid and base –
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-7

Question 16.
Write chemical formula of calcium hydroxide.
Answer:
Ca(OH)2

Question 17.
Write chemical formula of sodium hydroxide.
Answer:
NaOH

Question 18.
Write chemical formula of Magnisium hydroxide.
Answer:
Mg (OH)2

Short Answer type Questions:

Question 1.
From where the term ‘acid’ originated?
Answer:
Acid word comes from a Latin word Acidus which means sour. The acid is English term.

Question 2.
Bases turn red plant dyes into blue. Explain.
Answer:
Take petals of red colour flower in a taste tube filled with lime water (base). We will observe that red colour of petal turn to blue. so we can say that bases turn the red colour of vegetable dyes into blue.

Question 3.
What do you know about litmus?
Answer:
Litmus is the most common natural indicator which is used to identify acids and bases. It is obtained from Lichen (algae). It is present in forms of solution and paper strips. These paper sheets arc known as Litmus papers.
Litmus are of two types –

  1. Red Litmus and
  2. Blue Litmus.

Question 4.
What are neutralization reactions?
Answer:
Appropriate amount of acids and bases undergo continuous reaction and form salt and water with the release of heat. This reaction is called neutralization.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 5.
How can we test about nature of substances without tasting it ?
Answer:
Without tasting the substances. We can find out about nature of substances using indicators. They tell about nature of substances by changing their colour. They changes their colour by adding with substances.
These are of to types –

  1. Natural indicators and
  2. Artificial indicators.

Question 6.
Following are some natural sources of acids. Name the acids found in them –

  1. Vinegar
  2. Lemon
  3. Tomato
  4. Grapes
  5. Milk
  6. Tamarind
  7. Apple.

Answer:
Name of acids found- in their natural source
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-8

Question 7.
Explain an experiment of reaction between acid and metal with a diagram.
Answer:
Add a few drops of concentrated Sulphuric acid in a test tube and add zinc granules in it. We will observe bubbles in the test tube. On bringing the match stick flame near the mouth of the test tube, the flame burns with blue flame. This released gas is hydrogen. Hence it is concluded that acids form hydrogen (H2) gas on reacting with metals.
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-9

Question 8.
In houses we do not use metal containers for pickels, etc. ?
Answer:
In houses c do not use metal containers for pickels lemon juice. etc. because acids arc present in these food products which form poisonous substance on reacting with metals. Hence these food products are preserved in containers of glass. plastic or china day.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 9.
What are artificial indicators ? State their uses with an experiment.
Answer:
Artificial indicators arc man made which can be used as indicators. There arc two man made indicators.

  1. Phenolphthalein
  2. Methyl Orange.

Experiment –
Take two test tubes and label tham as A and B. Now add NaOH in test tube A and HCL in test tube B. Add phenolpthalene in test tube A and methyl orange in test tube B. solution of test tube A turns to pink and of test tube B turns to red. So we can say that phenolpthalene and methyl orange act like artificial indicators.

Question 10.
What are salts ? What are characteristics of these ?
Answer:
Salt : On reaction between acid & base. except water a new substance is also formed. which is known as salt.
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-10

Examples of salt –
Sodium chloride. (NaCl), Sodium carbonate (Na2CO3)

Characteristics of salts –

  1. Salts exists in solid state.
  2. Generally salt arc neutral.
  3. Aqueous solutions of salts are conductor of electricity.

Question 11.
Explain neutralization reaction with example.
Answer:
Sodium hydroxide (NaOH) on reaction with hydrochloric acid (HCl). produces sodium chloride (NaCl) and water with heat. It is neutralization reaction.
NaOH + HCl → NaCl + H2O + Heat
Hence reactions in which appropriate amount of acids and bases undergo continuous reaction and form salt and water with the release of heat. are known as neutralization reactions.

Question 12.
Comment on the following –

  1. Hydrochloric acid
  2. Sodium bi carbonate.

Answer:
1. Hydrochloric acid –
It is also called naniak Ka amle. Its chemical formula is HCl. It is used in toilet cleaners and purification of salt at industrial level.

2. Sodium bicarbonate –
It is often called baking soda. Its chemical formula is NaHCO3 It is used in houses for making baking powder, in making beverages, breads, cake. etc.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 13.
Write chemical formula of acids, bases and salts written here –

  1. Sulphuric acid
  2. Nitric acid
  3. Hydrochloric acid
  4. Acetic acid
  5. Sodium hydroxide
  6. Calcium oxide
  7. Sodium Chloride
  8. Sodium carbonate
  9. Sodium bicarbonate.

Answer:

  1. Sulphuric acid – H2SO4
  2. Nitric acid – HNO3
  3. Hydrochloric acid – HCl
  4. Acetic acid – CH3COOH
  5. Sodium hydroxide – NaOH
  6. Calcium oxide – CaO
  7. Sodium Chloride – NaCl
  8. Sodium Carbonate – Na2CO3
  9. Sodium bicarbonate – NaHCO3.

Question 14.
Write common names and their chemical formula, of following acids, bases and salts –

  1. Sulphuric acid
  2. Nitric acid
  3. Hydrochloric acid
  4. Acetic acid
  5. Sodium hydroxide
  6. Calcium oxide
  7. Sodium Chloride
  8. Sodium carbonates
  9. Sodium bicarbonate.

Answer:
Common names of some acids. bases & salts –
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-11

Essay type Questions:

Question 1.
What are indicators ? What are types of indicators ? Tell about natural indicators.
Answer:
Indicators –
To identify the nature of substance whether it is acidic or basic without touching or tasting. we use some special substances that are called indicators. So indicators tell the nature of substances by changing its colour. Eg. turmeric, litmus, petals of china rose. etc.

Types – Indicators are of two types –

  1. Natural indicators
  2. Artificial indicators

1. Natural indicators
(a) Litmus paper –
This is the most common natural indicator which is used to identify acids and bases. It is obtained from Lichen (algae). It is present in forms of solution and paper strips. These paper sheets are known as Litmus papers. Litmus are of two types – Red litmus and Blue litmus.

(b) Turmeric –
Turmeric is also a natural indicator. By adding few drops of lime water on turmeric paper, its yellow colour turns into red.

(c) Petals of China Rose –
Take petals of china rose in a beaker and add a small quantity of hot water in it. Keep it for few minutes until the colour of solution turns to light pink. This is china rose flowers indicator, This indicator makes acidic solution dark pink and basic solutions green.

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 2.
Give one example and use of acid, base and salt in our daily life.
Answer:

  1. Use of acids – cg. Hydrochloric acid which is also known as Namak Ka Amle. Its chemical formulae is HCl. It is used in toilet cleaners and purification of salt at industrial Level.
  2. Use of Base – cg. Calcium oxide, it is also known as Quick Lime. Its chemical formula is CaO. It is used in houses for white washing, treating wounds, for making ammonia and extraction of iron in industries.
  3. Use of salt – eg. Sodium bicarbonate. Its chemical formula is NaHCO3. It is also called baking soda. It is used in houses for making baking powder, in making beverages, breads, cake, etc.

Question 3.
Explain the soil treatment by neutralization reaction and also write other examples of ¡tin our daily life.
Answer:
In our daily life, there are so many uses & advantages of neutralization reactions. Some are as follows –

  1. Soil treatment
  2. treatment of acidity
  3. treatment of waste of industries.

Soil treatment –
Excess use of chemical fertilizers in fields turns the soil acidic which is harmful for growth of plants. Soil being more acidic or basic reduces the fertility of soil hence when soil is more acidic, quick lime is mixed which is basic in nature and reduces acidity of a soil. When the soil is basic, fertilizers are mixed in soil which reduces the basicity of soil.

Question 4.
Tell about the effect of following substances on blue and red litmus papers – Lemon Juice, pond water, detergent solution aerated beverages, soap water, shampoo, salt solution, sugar solution, vinegar, baking soda solution, milk of magnesia, baking soda solution, lime water.
Answer:
Effect of substances on Red & Blue litmus papers –
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts-12

Question 5.
Write uses of acids, bases and salts in our daily life with examples in detail.
Answer:
(a) Uses of Acids –
1. Sulphuric acid (H2SO4) –
It is also called as gandhak Ka amle. It is used in industries for formation of fertilizers like formation of ammonium sulphate, in batteries, dyes, clothes, and paper industries.

2. Nitric acid (HNO3) –
It is also known as shore ka amle. It is used in industrial scale in purification of Gold & Silver. in making of crackers, for making fertilizers, and for other explosives like TNT, dynamite.

3. Hydrochloric acid (HCl) –
It is also called as namak ka amie. It is used in toilet cleaners and purification of salt at industrial level.

(b). Uses of bases –
1. Sodium hydroxide (NaOH) – It is often called caustic soda. It is used in houses for cleaning of utensils and for making soaps in industries.

2. Calcium oxide (CaO) – It is called as quick lime, it is used in houses for white washing and treating wounds and for making ammonia and extraction of iron in industries.

(c) Uses of Salts:
1. Sodium chloride – (NaCl) – It is also known as common salt/table salt. It is used in houses in food and for making chlorine in industries.

2. Sodium Carbonate – It is often called washing soda. It is used in houses for washing clothes and for softening of water in industries.

3. Sodium bicarbonate – It is often called baking soda. It is used in houses for making baking powder, in making beverages, breads, cake etc. and for making sodium carbonate and for making digestive substances in industries.

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