CBSE Class 7 Science Acids Bases and Salts Assignment

Following questions consists of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
A. Both assertion and reason are true, and reason is the correct explanation of assertion.
B. Both assertion and reason are true, but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Assertion is false and reason is true.

Question. Assertion (A): Honey bee-sting injects an acid in the skin which causes pain and irritation.
Reason (R): Use of mild base like baking soda on the stung area gives relief.

Answer: B

Question. Assertion(A): NaHCO3+ HCl = NaCl + H2O + CO2
Reason (R): Evolved gas catches fire immediately.

Answer: ​​​​​​​C

Question. Assertion: NaOH reacts with zinc metal and produces hydrogen gas.
Reason: Acids react with active metals to produce hydrogen gas.

Answer: ​​​​​​​B

Question. Assertion(A): Baking powder is used in making cake instead of using only baking soda.
Reason(R) : Baking powder contains Tartaric acid which reacts with sodium carbonate and removes bitter taste.

Answer: ​​​​​​​C

Question. Assertion(A): Plaster of Paris is stored in moisture proof containers.
Reason(R) : Plaster of Paris sets into a hard mass on coming in contact with water to form anhydrous Calcium Sulphate.

Answer: ​​​​​​​C

Question. Assertion(A): The chemical formula of bleaching powder is CaOCl2.
Reason(R): Chlorine gas is passed over Calcium Oxide to form bleaching powder.

Answer: ​​​​​​​A

Question. Assertion(A): Soda-acid fire extinguisher contains sodium hydrogen carbonate and sulphuric acid.
Reason(R): Sulphuric acid mixes with sodium hydrogen carbonate solution and produces a lot of CO2 gas, which forms a blanket over fire and cuts it off from the supply of the air to the burning substance and the fire stops.

Answer: A

Question. Assertion(R): The compound prepared from gypsum on heating it at 373 K , is known as Plaster of Paris.
Reason(R): Plaster of Paris is used in hospitals mainly as plaster for supporting fractured bones in the right position. In dentistry, it is used for making casts.

Answer: ​​​​​​​B

Question. Assertion(A):.Washing soda is a chemical compound that can be used to remove stubborn stains from laundry
Reason(R):The sodium carbonate in washing soda "softens" water.

Answer: ​​​​​​​B

Question. Assertion(A): Bleaching powder is CaOCl2, and is prepared from chlorine and slaked lime
Reason(R):Bleaching powder can be used for bleaching, disinfecting, oxidation.

Answer: ​​​​​​​C

I. Fill in the blanks:-

1. An acid is ____________ by a base .

2. Phenolphthalein is an __________ indicator.

II. Choose the correct option:-

1. A Soap Solution is –

a) Basic b) Acidic c) Alkaline d) Neutral

2. CO₂ + H₂O →

a) Sulphuric acid b)Nitric acid c) Carbonic acid d) None

III Name the following:-

1. Soluble bases.

2. A Chemical used as a food preservative.

3. Chemical name of Chile Salt Petre.

IV Define the following:-

1. Acid Rain 2. Neutralisation Reaction 3. Acid-Base Indicator

V Give Reasons:-

1. Non Metal Oxides are called Acidic .

2. Metal Oxides are Basic

3. Sour things are not kept in metal pots

4. Metal Oxides such as MgO are used for making refractory bricks.

VI Complete the Equations:-

1. ________ + 2O₂ → CO₂ + H₂O

2. 3NO₂ + H₂O → NO + _______ .

3. 2NaOH + H₂SO₄ → _________ + 2H₂O

4. CaCO₃ → ________ + CO₂

VII Answer in 20 words :-

1 Name three mineral acids and give their formulae?

2 What is acid and base?

VIII Answer in 40 words:-

1. What are general properties of bases?

2. What are general properties of acids?

3. Name an acidic gas which is discharged into the atmosphere on the burning of fuels like coal

& natural gas. How is this gas formed?

IX Answer in 100 words:-

1. Describe an activity to show the effect of acid on carbonates and hydrogen carbonates?

2. What is acid rain? How is it formed? Mention three bad effects of acid rain .

X Write one use of the following:-

1. Sulphuric acid.

2. Citric acid

3. Sodium Carbonate

4. Potassium Nitrate

5. Calcium phosphate

Q.1 Fill in the blanks.

i) An acid testes s_______________

ii) A base tastes b__ tt____________

iii) LItmus, a natural indicator is extracted from Li_____________.

iv) An indicator used in a neutralisation reaction is phe___ph_____lein.

v) Sugar is a n....u............l substance.

Q.2 Match the following.

         Column I                      Column II

a) An antacid                    i) Formic acid

b) An Ant                         ii) Milk of magnesia

c) China Rose                iii) Turns red litmus blue.

d) An acid                       iv) A natural indicator

e) A base                        v) Turns blue litmus red.

Answer : a. b. c. d. e.

Q.3 Bring a soil sample of your area, find out weather it is acidic, basic or neutral with the help of red or blue litmus solution /paper. Write this observation in the space given below.

Q.4 According to their nature give proper place to each substance given below. 

Curd, Common Salt, Vinegar, Soap, Sugar, Lime water, Lemon Juice, Window Cleaner.

1. Acidic Nature .................

2. Basic Nature .................

3. Neutral Substances .................

Q.5 Complete the following table