Unit-1: Chemical Reactions and Equations – Chemistry NCERT Solution Grade-X

Unit-1: Chemical Reactions and Equations


Textbook Intext Questions:-


Q.Why should magnesium ribbon be cleaned before burning in air ?

Q.Write the balanced equation for the following chemical reactions:-
(i) Hydrogen + Chlorine –> Hydrogen chloride
(ii) Sodium + Water –> Sodium hydroxide + Hydrogen

Q.Write a balanced chemical equation with state symbols for the following chemical reactions:
(i) Solution of barium chloride and sodium sulphate in water to give insoluble barium sulphate and the solution of sodium chloride.
(ii) Sodium hydroxide solution (in water) react with hydrochloric acid solution (in water) to produce sodium chloride and water.

Q. A reaction of a substance X is used for white washing.
(i) Name the substance X and write its formula.
(ii) Write the reaction of the substance X named in (i) above with water.

Q.Why is the amount of gas collected in one of the test tubes in Activity 1.7, double of the amount collected in the other ? Name this gas.

Q.Why does the colour of copper sulphate solution change when an iron nail is dipped in it ?

Q.Give an example of the double displacement reaction other than the one given in Activity 1.10.

Q.Identify the substances that are oxidized and the substances that are reduced in the following reactions:

(i) 4Na(s) + O2(g) –> 2Na2O(s)
(ii) CuO(s) + H2(g) –> Cu(s) + H2O(liq)


Textbook Exercise :-


Q.1: Which of the statements about the reaction below are incorrect?
2PbO + C —> 2Pb + CO2­
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidized.
(c) Carbon is getting oxidized.
(d) Lead oxide is getting reduced.
(i) a and b (ii) a and c (iii) a, b and c (iv) all.

Q.2: Fe2O3 + 2Al —> Al2O3 + 2Fe
The above reaction is an example of a
(a) combination reaction
(b) double displacement reaction
(c) decomposition reaction
(d) displacement reaction.

Q.3: What happens when dilute HCl is added to iron filings ? Tick the correct answer.
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced.

Q.4: What is a balanced chemical equation ? Why should chemical equation be balanced ?

Q.5: Translate the following statements into balanced chemical equations.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Q.6: Balance the following chemical equations.
(a) HNO3 + Ca(OH)2 —> Ca(NO3)2 + H2O
(b) NaOH + H2SO4 —> Na2SO4 + H2O
(c) NaCl + AgNO3 —> AgCl + NaNO3
(d) BaCl2 + H2SO4 —> BaSO4 + HCl

Q.7: Write balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide —> Calcium carbonate + Water
(b) Zinc + Silver Nitrate —> Zinc nitrate + Silver
(c) Aluminium + Copper chloride —> Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate —>. Barium sulphate + Potassium chloride

Q.8: Write the balanced chemical equations for the following and identify the type of reaction in each case.
(a) Potassium bromide + Barium iodide —> Potassium iodide + Barium bromide
(b) Zinc carbonate —> Zinc oxide + Carbon dioxide
(c) Hydrogen + Chlorine —> Hydrogen chloride
(d) Magnesium + Hydrochloric acid —> Magnesium chloride + Hydrogen

Q.9: What does one mean by exothermic and endothermic reactions? Give examples.

Q.10: Why is respiration considered an exothermic reaction? Explain.

Q.11: Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

Q.12: Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

Q.13: What is the difference between the displacement and double displacement reactions? Write equations for these reactions.

Q.14: In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

Q.15: What do you mean by a precipitation reaction? Explain by giving examples.

Q.16: Explain the following in terms of gain or loss of oxygen with two examples each.

Q.17: A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

Q.18: Why do we apply paint on iron articles ?

Q.19: Oil and fat containing food items are flushed with nitrogen. Why ?

Q.20: Explain the following terms with an example each:
(a) Corrosion (b) Rancidity