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

RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts are part of RBSE Solutions for Class 7 Science. Here we have given Rajasthan Board RBSE Class 7 Science Chapter 5 Acids, Bases and Salts.

Board RBSE
Textbook SIERT, Rajasthan
Class Class 7
Subject Science
Chapter Chapter 5
Chapter Name Acids, Bases and Salts
Number of Questions Solved 59
Category RBSE Solutions

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

Textbook Exercise

Multiple Choice Questions

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) Magic acid
Answer:
(c) Washing soda

Question 3.
Gas formed by 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 acids and bases forms and ………………….
3. Acid reacts with sodium bicarbonate and evolves …………… gas.
4. HCl + NaOH → ……………  + ……………..
Answer:
1. Blue
2. Salt, water
3. carbon dioxide
4. NaCl + H2O

Match the Columns

Column A Column B
1. Sodium Chloride (a) H2SO4
2. Acid of sulphur (b) NaHCO3
3. Baking soda (c) NaCl
4. Vinegar (d) CaO
5. Quicklime (e) CH3COOH

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:
Litmus and Turmeric.

Question 2.
In which reaction do acids and bases react to form salt and water?
Answer:
Acids and bases react to form salt and water in neutralisation reaction.

Question 3.
Write three properties of bases.
Answer:
Properties of bases:

  1. They are bitter in taste.
  2. Soapy to touch.
  3. Turns red litmus blue.

Question 4.
A blue litmus is dipped in a solution. It becomes red. Write the nature of solution. Explain it.
Answer:
The nature of solution is acidic. Acids turns blue litmus red.

Question 5.
What is acidity? Write its treatment.
Answer:
The hydrochloric acid secreted in our stomach is helpful in digestion. But if the acid secreted by stomach is more than required, it causes indigestion. This is known as acidity. To relieve this, antacids like milk of magnesium (magnesium hydroxide) is used. It neutralises the effect of extra acids present in stomach.

Question 6.
What happens if waste materials of industries is drained off without treatment?
Answer:
In waste materials of industries, acid is present. If these wastes are disposed directly into water bodies then it will be dangerous for fishes, aquatic plants and animals.

Question 7.
Why do we not use metal containers to keep lemon juice?
Answer:
Lemon juice contains acid which react with metal container and form poisonous substances. Therefor, such containers are not used for keeping lemon juice.

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: Indicators are substances which show a change in colour when brought in contact with acids and bases. These indicators indicate the nature of a substance by colour change. Names of two indicators: Litmus, turmeric.

Effects of indicators on acids and bases:
Acids turns bulb litmus red and bases turns red litmus blue. Bases mixed in solution of turmeric powder gives red colour.

Question 2.
Write three differences between acids and bases.
Answer:
Difference between acids and bases:

Acids Bases
1. Sour in taste. 1. Bitter in taste
2. Changes blue litmus red. 2. Changes red litmus blue.
3. Not soapy to touch. 3. Soapy to touch.

Question 3.
Write uses of the following:
(a) Washing soda
(b) Sodium chloride
(c) Sulfuric Acid
(d) Calcium Oxide
(e) Acetic acid
Answer:
(a) Used for washing clothes
(b) Sodium chloride is common salt. It is used in food
(c) Sulfuric Acid or Acid of sulphur is used in toilets by diluting
(d) Calcium oxide is used in white washing
(e) Acetic acid is used in making pickles.

Intext Questions

Question 1.
You had used eatables like lemon, tamarind, orange, apple, sugar and salt. Did all the substances taste same? (page 46)
Answer:
No, all substances have different taste.

Question 2.
Why lime, orange juice, tamarind etc. sour in taste. (page 47)
Answer:
Because acid is present in these.

Question 3.
What are acids? (page 47)
Answer:
The substances that are sour in taste are acids.

Question 4.
What is the taste of baking soda? (page 49)
Answer:
Baking soda tastes bitter.

Question 5.
How do we feel when solution of baking soda is rubbed on our hand? (page 49)
Answer:
It is soapy to touch.

Question 6.
Is it possible to identify the nature of unknown substances of their taste ? (page 50)
Answer:
No, because tasting or touching any substance without identifying maybe harmful.

Question 7.
What are salts? (Page 53)
Answer:
The substance formed in addition to water when acid and base react with each other is called salt.

Activities

Activity 1: (Page 46)
Question: Tabulate the taste of different food items:
Answer:

S.No Food Products or items Taste (sour/sweet)
1 lemon juice sour
2 orange juice sour
3 Amla sour
4 tamarind sour
5 Neem bitter
6 Sugar sweet
7 Salt salty
8 Banana sweet
9 Butter tasteless / salty

Activity 2: (Page 47)
Objective: To know properties of acids.
Method:

  1. Take some baking soda in a glass.
  2. Add few drops of lime juice in it.

Question 1.
What do you observe?
Answer:
We observe that foam or bubbles appear in the glass and a gas is released.
3. When a burning match stick is brought near the gas, the stick extinguishes.

Question 2.
Why matchstick blows out ?
Answer:
Acid reacts with baking soda and releases carbon dioxide gas. It blows out the matchstick.
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts 1
Conclusion: Acid reacts with baking soda and releases carbon dioxide gas.

Activity 4: (Page 49)
1. Take petals of blue colour flower and put them in a test tube filled with a small amount of acid.
Question 1.
What do you observe?
Answer:
We observe that colour of petal changes to red from blue.
Conclusion: This activity shows that acids turn colour of blue petal in to red.
RBSE Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts 2
Activity 6: (Page 51)

  1. Take some turmeric powder in a spoon.
  2. Mix small amount of water in it and make a paste.
  3. Spread this paste in a piece of white paper.
  4. Cut into small strips after drying.
  5. Now put some drops of lime water on turmeric paper.

Question 1.
What do you observe?
Answer:
The colour of turmeric changes from yellow to red.

Question 2.
Test due to bases solution given in table and fill/note the conclusion table.

S. No. Test solution Effect of turmeric paper on solution Conclusion
1 Amla juice turmeric colour acidic
2 Lemon juice turmeric colour acidic
3 Lime water colour becomes red basic
4 Curd turmeric colour acidic
5 Milk of Magnesia colour becomes red basic

Activity 9: (Page 53)
Question 1.
Why it happens so?
Answer:
NaOH reacts with HCl and forms NaCl and water and heat is released. Pink colour disappears because of neutrality of the solution

Other Important Questions

Multiple choice questions
Question 1.
Tomato contains
(a) Ascorbic acid
(b) Tartaric acid
(c) Citric acid
(d) Acetic acid
Answer:
(a) Ascorbic acid

Question 2.
Used in fire extinguishing
(a) Hydrogen gas
(b) Oxygen gas
(c) carbon dioxide
(d) All the above
Answer:
(c) carbon dioxide

Question 3.
Litmus is obtained by
(a) Lichen
(b) Fungi
(c) Bacteria
(d) Organisms
Answer:
(a) Lichen

Question 4.
Formula of caustic soda is
(a) KOH
(b) NaHCO3
(c) NaCl
(d) NaOH
Answer:
(d) NaOH

Question 5.
The formula of common salt is
(a) NaCl
(b) NaOH
(c) NaHCO3
(d) Na2CO3
Answer:
(a) NaCl

Fill in the blanks:
1. Acid is derived from word ……….
2. Acids turns blue indicators to ……………
3. The substances which have no effect on litmus paper are called ……………… substances.
4. Aqueous solution of ……………. are good conductors of electricity.
5. …………….. is generally known as acid of Salt.
Answer:
1. Acidus
2. red
3. Neutral
4. Salt
5. Hydrochloric acid

Very Short answer Type Questions
Question 1.
Which acid is found in orange and grapes?
Answer:
In oranges, citric acid is found and in grapes, tartaric acid is found.

Question 2.
Write the chemical name of baking soda.
Answer:
Sodium bicarbonate.

Question 3.
What happens when acid reacts with baking soda?
Answer:
Carbon dioxide gas is released when acid reacts with baking soda.

Question 4.
What happens when acid reacts with zinc?
Answer:
Hydrogen gas is released when acid reacts with zinc.

Question 5.
Write the name of two artificial indicators.
Answer:
Phenolphthalein and Methyl orange.

Question 6.
What is the chemical name of caustic soda?
Answer:
Sodium hydroxide (NaOH).

Question 7.
What is the chemical name of Vinegar?
Answer:
Acetic acid (CH3COOH).

Question 8.
What are antacids?
Answer:
The substances which neutralises the effect of acids are called antacids.

Short Answer Type Questions
Question 1.
What are acids? Write the name of two food items which contain acids.
Answer:
The word acid is derived from Latin word’ Acids’ which means sour. Hence, we can say that the substances which are sour in taste are called acids. Two food items which contain acid: Orange and curd.

Question 2.
Write two chemical properties of acids.
Answer:

  1. Acids react with sodium bicarbonate and releases carbon dioxide gas.
  2. Acids react with metals and releases hydrogen gas.

Question 3.
Write the name and chemical formula of bases present in the following substances:
1. Lime water
2. Soaps
3. Milk of Magnesia
Answer:

  1. Limewater – Calcium hydroxide- (Ca (OH)2)
  2. Soaps – Sodium hydroxide – NaOH
  3. Milk of Magnesia – Magnesium Hydroxide (Mg (OH2))

Question 4.
What are neutral substances? Explain with examples.
Answer:
The substances which do not show any colour change with litmus paper are called neutral substances. These substances are neither acidic nor basic. For example, salt, ammonium chloride, calcium chloride, sodium carbonates, sodium bicarbonates etc.

Question 5.
Write the role of acids and bases in soil treatment. .
Answer:
Excessive use of chemical fertilisers in fields make soil acidic which is harmful for growth ofplants. More acidity or basicity of soil decreases the fertility of the soil. Therefore, to reduce acidity of soil quick lime or slaked lime is mixed in the soil. If soil is basic, then organic products in the form of manure is mixed in the soil.

Question 6.
What is the role of bases in disposal of wastes from factories ?
Answer:
Acidic substances are present in industrial wastes. If these wastes are directly disposed into the water, then it may be harmful for fishes, aquatic plants and other aquatic animals. Therefore, basis substances are mixed in these wastes to neutralise them.

Long Answer Type Questions
Question 1.
Write the name of some natural acids and their sources.
Answer:

  1. Vinegar: Acetic acid
  2. Apple: Malic acid
  3. Tamarind: Tartaric acid
  4. Milk: lactic acid
  5. Lemon: Citric acid
  6. Tomato: Ascorbic acid
  7. Grapes: Tartaric acid

Question 2.
(a) What is litmus? How is litmus paper obtained?
(b) Write the method of preparation of turmeric paper.
Answer:
Litmus: To determine acidity or basicity of any substance, litmus is most commonly used as natural indicator. Litmus is obtained from lichen. It is used both as a solution and as strips of paper. These strips of paper are called litmus paper. There are two types of litmus papers: Red litmus and blue litmus.
(a) Lichen
(b) Red and Blue Litmus Paper Turmeric paper: Take some turmeric powder in a spoon. Mix small amount of water in it and make a paste. Spread this paste in a piece of white paper. Cut into small strips after drying. Now, turmeric paper is ready to use.

Question 3.
1. What are neutralisation reactions? Explain with the help of a chemical equation?
2. Write the names of products of neutralisation reaction and write the properties of main products of neutralisation.
Answer:
1. Neutralisation reaction: The process in which a definite amount and volume of acid and base react to form salt and water. A large amount of heat is also produced in the reaction.
This process is called Neutralisation. For example:
NaOH + HCl → NaCl + H2O + heat

2. A new substance is formed from acid and base called salt. For example, sodium chloride, sodium carbonate, sodium bicarbonate etc. These are neutral in nature. It can be tested by using litmus paper.These do not show any colour change to litmus paper.
Properties of salt:

  1. These are generally found in solid state.
  2. These are generally neutral.
  3. These are good conductors in aqueous solution.

Question 4.
Write the uses of four acids.
Answer:

  1. Sulphuric acid: It is generally known as Acid of Sulphur. Its chemical formula is H2SO4. It is used in preparation of fertilisers like ammonium sulphate, in batteries, in colouring, textile industries etc.
  2. Nitric acid: Its chemical formula is HNO. It is used in preparation of aqua regia, ammonium nitrate fertilisers, purification of gold and silver, crackers and explosives, T.N.T, dynamite etc.
  3. Hydrochloric acid: It is generally known as acid of salt. Its chemical formula is HCl. It is used in toilet cleaning and in formation of chlorine and salt at industrial level.
  4. Acetic acid: It is generally known as Vinegar. Its chemical formula is CH3COOH. It is used in making pickles, medicines and in cellulose acetate (photo film).

Question 5.
(a) Write two characteristics of bases.
(b) Write the uses of any two bases.
Answer:
(a) 1. bases are bitter in taste and soapy to touch.
2. They turn red litmus blue.
(b) 1. Sodium hydroxide: It is also known as Caustic soda. Its chemical formula is NaOH. It is used in washing utensils and formation of soaps.
2. calcium oxide: It is known as quick lime. Its chemical formula is CaO. It is used in white washing and in formation of ammonia, extraction of iron etc,

Question 6.
Write the uses of the following:
1. Sodium chloride.
2. Sodium carbonate
3. Sodium bicarbonate
Answer:

  1. Sodium chloride: It is called table salt. Its chemical formula is NaCl. It is used in food and in the formation of chlorine.
  2. Sodium carbonate: It is generally known as washing soda. Its chemical formula is Na2CO3. It is used in washing clothes and in removal of hardness of water.
  3. Sodium bicarbonates: It is also known as Baking soda. Its NaHCO3. It is used in formation of baking soda, drinks, breads, cakes etc. On industrial level, it is used in preparation of sodium carbonate and digestive substances.

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