Class 10 Science Chapter 1 Chemical Reaction and Equations The answer to each chapter is provided in the list so that you can easily browse throughout different chapters NCERT Class 10 Science Chapter 1 Chemical Reaction and Equations and select need one.
Class 10 Science Chapter 1 Chemical Reaction and Equations
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Additional Questions and Answers
Q.1. What is a chemical equation?
Ans :- A chemical equation is an expression for gives chemical change in terms of symbols or formula of the reactants and products.
Q.2. How do we came to know that a chemical reaction has taken place?
Ans :- Any of the following observations helps us to determine whether a chemical reaction has taken place.
(a) Change in stale.
(b) Change in colour.
(c) Evolution of gas.
(d) Change in tempe rature.
Q.3. How magnesium oxide is formed ?
Ans :- Magnesium oxide is formed due to the reaction between magnesium and oxygen present in the air.
Q.4. When an unbalanced equation formed ?
Ans :- If the number of atoms of each element are not same on the both sides then an unbalanced equation formed.
Q.5. What is combination reactions? Give one example?
Ans :- A reactions in which a single product is formed fro two or more reactants is known as a combination reaction.
For example :- CaO + H₂O → Ca(OH)₂
Q.6. Give two examples of exothermic reactions?
Ans :- (i) Burning of natural gas CH₄ (g) + 2O₂(g) → CO₂ + 2H₂O (g)
(ii) The decomposition of vegetable matter into compost is an example of an exothermic reaction.
Q.7. What is thermal decomposition? Give two examples.
Ans :- When a decomposition reaction is carried out by heating it is called thermal decomposition.
Example :-
Q.8. Why silver chloride turns grey in sunlight ?
Ans :- This is due to the decomposition of silver chloride into silver and chlorine by light.
Q.9. Balance the following skeletal equations-
(i) KCIO₃ → KCI + O₂
(ii) CH₄ + O₂ → CO₂ + H₂O
(iii) Nacl + H₂SO₄ → Na₂So₄ + HCI
(iv) H₂S + O₂ → H₂O + S
(v) H₂ + N₂ → NH₃
Ans. (i) 2KCIO₃ → 2KCI + 3O₂
(ii) CH₄ + 2O₂ → CO₂ + 2H₂O
(iii) 2Nacl + H₂SO₄ → Na₂So₄ + 2HCI
(iv) 2H₂S + O₂ → 2H₂O + 2S
(v) 3H₂ + N₂ → 2NH₃
Q.10. What is the need to balance a chemical equation with respect to mass and change?
Ans :- The chemical equation must be balanced with respect to mass because matter can neither be created nor destroyed. The equation must be balanced with respect to charge because the electrons lost by atoms to form cations are equal to the electrons gained by other atoms to form anions. Thus, as the reaction mixture does not contain any free electrons, the total positive change should be equal to the total negative charge.
Q.11. Identify the substance oxidized and reduced in the chemical reaction.
MnO₂ + 4HCI → MnCI₂ + Cl₂ + 2H₂O
Ans :- oxidised :- HCI
Reduced :- MnO₂
Q.12. Milk becomes sour if kept for a long time, what is the type of reaction?
Ans :- Decomposition reaction.
Q.13. Give two necessary conditions for rusting?
Ans :- (i) Presence of air or oxygen.
(ii) Presence of moisture.
Q.14. How is rusting of iron prevented ?
Ans :- Prevention of rusting :
(i) The iron articles should be painted.
(ii) Iron can be coated with chromium.
(iii) The machine parts should be oiled and greased.
(iv) Galvanised iron pipes are used for water supply.
Q.15. Name the type of reactions :
(i) Fe(s) + CuSO₄(aq) → Cu(s) + FeSO₄(aq)
(ii) 2NH₃(g) → N₂(g) + 3H₂(g)
(iii) HN₄Cl (s) → NH₃ (g) Hcl (g)
(iv) 2H₂ (g) + O₂ (g) → 2H₂O (g)
(v) Mg(s) + H₂SO₄ (aq) – MgSO₄ (aq) + H₂ (g)
Ans :- (i) Displacement reaction.
(ii) Decomposition reaction.
(iii) Decomposition reaction.
(iv) Combination reaction.
(v) Displacement reaction.
Q.16. How are the following information indicated in a chemical equation ?
(i) Formation of a precipitate.
(ii) Evolution of a gas.
(iii) A solution made in water.
(iv) Evolution of heat.
(v) Absorption of heat.
Ans :- (i) ↓or (s)
(ii)↑or (g)
(iii) (aq)
(iv) + heat (∆ H = – ve)
(v) – heat (∆ H = + ve)
Q.17. What is a redox reaction?
Ans :- a chemical reaction in which one substance oxidised and the other is reduced is called a redox reaction. All oxidation reduction reaction are redox reaction. In a chemical reaction, a substance get oxidised only when another substance is present gets reduced.
Q.18. Give two differences between rusting and burning.
Ans :- (i) Rusting is a slow process while burning is a fast process.
(ii) Rusting takes place in the presence of oxygen and moisture while burning requires only oxygen.
Q.19. Fill in the blanks.
(i) New substances formed during a chemical change are ———— .
Ans :- Product.
(ii) Fe+CuSo₄ → FeSO₄ + Cu is ——– reaction.
Ans :- Displacement.
(iii) The reaction which proceeds by evolution of heat is known as ———- .
Ans :- Exothermic reaction.
(iv) Decomposition reactions are the opposite of———— reactions.
Ans :- Combination.
(v) The gain of hydrogen by au atom or ion is known as———- .
Ans :- Reduction.
(vi) The comparative reactivity of metal is shown by———— reactions.
Ans :- Displacement.
(vii) More reactive metal displaces ———– metal from its salt solution.
Ans :- Less Reactive.
(viii) The digestion of food in our body is indicative of————– reaction.
Ans :- Décomposition.
(ix) Electrons are lost and gained during———–reactions.
Ans :- Redox.
Q.20. How can rancidity be prevented ?
Ans :- By adding antioxidants to food.
MULTIPLE CHOICE QUESTIONS
Q.1. In a chemical equation, what is avoided ?
(a) Symbols.
(b) Formula.
(c) Number of atoms. And
(d) Words.
Ans :- (d) Words.
Q.2. Choose the double displacement reaction
(a) X+ YZ → XY + Z
(b) X + Y → XY
(c) XYZ → YZX
(d) XY + AB → XA + YB
Ans :- (d) XY + AB → XA + YB
Q.3. Which is true for an oxidation reaction ?
(a) Addition of oxygen.
(b) Removal of oxygen.
(c) Removal of hydrogen.
(d) Addition of hydrogen.
(i) (a) and (c)
(ii) (a) and (d)
(iii) (a) and (b)
(iv) (b) and (d)
Ans :- (i) (a) and (c)
Q.4. Which one of the following can be a non-redox reaction ?
(a) Combination.
(b) Decomposition.
(c) displacement.
(d) Double displacement.
Ans :- (d) Double déplacement.
Q.5. Identify the double decomposition reactions.
(a) Hydrogen burns in air.
(b) Electrolysis of water.
(c) Digestion of food.
(d) Addition of dilute sulphuric acid to BaCl₂ solution.
Ans :- (d) Addition of dilute sulphuric acid to BaCl₂ solution.
Q.6. Choose the combination reaction.
(a) Electric current is passed through water.
(b) Hydrogen burns in oxygen.
(c) Hydrogen peroxide is exposed to sunlight.
(d) Digestion of food in our body.
Ans :- (b) Hydrogen burns in oxygen.
Q.7. Food items on exposures to atmosphere become rancid due to the process of.
(a) Oxygen.
(b) Reduction.
(c) Corrosion.
(d) Hydrogenation.
Ans :- (a) Oxidation.
Q.8. What is not true in a balanced chemical equation ?
(a) Number of atoms of different elements on both sides are equal.
(b) Mass of both sides are equal.
(c) Number of charged ions on both sides are equal.
(d) Total of charges on both sides are equal.
Ans :- (c) Number of charged ions on both sides are equal.
Q.9. Respiration is a chemical change because.
(a) Energy is evolved.
(b) There is decrease in temperature.
(c) There is increase in temperature.
(d) There is change in state.
Ans :- (a) Energy is evolved.
Q.10. In which of the following experiments, residue left behind is reddish-brown ?
(a) Heating of coper powder in air.
(b) Heating of ferrous sulphate crystals.
(c) Heating of magnesium in air.
(d) Heating of solid calcium carbonate.
Ans :- (b) Heating of ferrous sulphate crystals.
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