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Science class 10

Chemical Equations and Reactions Worksheet

Chemistry Questions with Answers

Question 1:

What is the general name of the chemicals which are added to fat and oil containing foods to prevent the development of rancidity?

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Anti-oxidants.

Question 2:

State an important use of decomposition reactions.

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The digestion of food in the body is an example of decomposition reaction.

Question 3:

What are anti-oxidants? Why are they added to fat and oil containing foods?

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Anti-oxidants are substances which prevent oxidation. They are added to fat and oil containing foods so that they do not get oxidized easily and hence do not turn rancid.

Question 4:

Explain why food products containing fats and oils (like potato chips) are packaged in nitrogen.

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Food products containing fats and oils are packaged in nitrogen so that there is no oxygen to cause oxidation of food and make it rancid.

Question 5:

Give one example of a decomposition reaction which is carried out:

  1. with electricity
  2. by applying heat
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(a) When fused sodium chloride is decomposed by passing electricity, sodium metal is obtained.

(b) When lead nitrate is heated strongly, it breaks down to form lead monoxide, nitrogen dioxide and oxygen.

Question 6:

What type of chemical reaction is used to extract metals from their naturally occurring compounds like oxides or chlorides?

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Decomposition reactions (carried out by electricity).

Question 7:

Name two anti-oxidants which are usually added to fat and oil containing foods to prevent rancidity.

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BHA (Butylated Hydroxy Anisole) and BHT (Butylated Hydroxy Toluene).

Question 8:

Write one equation each for the decomposition reactions where energy is supplied in the form of:

  1. heat
  2. light
  3. electricity
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(a) Decomposition of calcium carbonate: CaCO3 → CaO + CO2 (by heat)

(b) Decomposition of silver chloride: 2AgCl → 2Ag + Cl2 (by light)

(c) Decomposition of water: 2H2O → 2H2 + O2 (by electricity)

Question 9:

In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the chemical equation of the reaction involved.

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2AgNO3 (aq) + Cu (s) → Cu(NO3)2 (aq) + 2Ag (s)

Question 10:

What type of reactions are represented by the following equations?

  1. CaCO3 → CaO + CO2
  2. CaO + H2O → Ca(OH)2
  3. 2FeSO4 → Fe2O3 + SO2 + SO3
  4. NH4Cl → NH3 + HCl
  5. 2Ca + O2 → 2CaO
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Decomposition.

Combination.

Decomposition.

Decomposition.

Combination.

Question 11:

What type of chemical reactions take place when:

  1. a magnesium wire is burnt in air?
  2. lime-stone is heated?
  3. silver bromide is exposed to sunlight?
  4. electricity is passed through water?
  5. ammonia and hydrogen chloride are mixed?
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(a) Combination.

(b) Decomposition.

(c) Decomposition.

(d) Decomposition.

(e) Combination.

Question 12:

What type of chemical reactions are represented by the following equations?

  1. A + BC → AC + B
  2. A + B → C
  3. X → Y + Z
  4. PQ + RS → PS + RQ
  5. A2O3 + 2B → B2O3 + 2A
Show Answer

Displacement reaction.

Combination reaction.

Decomposition reaction.

Double displacement reaction.

Displacement reaction.

Question 13:

Balance the following chemical equations:

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4Na + O2 → 2Na2O

2H2O2 → 2H2O + O2

Mg(OH)2 + 2HCl → MgCl2 + 2H2O

4Fe + 3O2 → 2Fe2O3

2Al(OH)3 → Al2O3 + 3H2O

2NH3 + 3CuO → 3Cu + N2 + 3H2O

Al2(SO4)3 + 6NaOH → 2Al(OH)3 + 3Na2SO4

2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O

2NaOH + H2SO4 → Na2SO4 + 2H2O

BaCl2 + H2SO4 → BaSO4 + 2HCl

Question 14:

Fill in the following blanks with suitable words:

  1. (a) Chemical equations are balanced to satisfy the law of…….
  2. (b) A solution made in water is known as an………. solution and indicated by the symbol…………….
Show Answer

(a) Conservation of mass

(b) Aqueous; (aq)

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