NCERT Class 10 Science Textbook made Screen Readable by Raunak Padhi from USA and Dr T K Bansal.

Q1. Which of the statements about the reaction below are incorrect?

$$2PbO (s) + C (s) → 2Pb (s) + CO_2 (g)$$

(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.

(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all

Q2.
$$Fe_2O_3 + 2Al → Al_2O_3 + 2Fe$$

The above reaction is an example of a
(a) combination reaction.
(b) double displacement reaction.
(c) decomposition reaction.
(d) displacement reaction.

Q3. What happens when dilute hydrochloric acid is added to iron fillings? 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.

Q4. What is a balanced chemical equation? Why should chemical equations be balanced?

Q5. Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas 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.

Q6. Balance the following chemical equations
(a) HNO3 + Ca(OH)2 equals Ca(NO3)2 + H2O
(b) NaOH + H2SO4 equals Na2SO4 + H2O
(c) NaCl + AgNO3 equals AgCl + NaNO3
(d) BaCl2 + H2SO4 equals BaSO4 + HCl

Q7. Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide equals Calcium carbonate + Water
(b) Zinc + Silver nitrate equals Zinc nitrate + Silver
(c) Aluminium + Copper chloride equals Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate equals Barium sulphate + Potassium chloride

Q8. Write the balanced chemical equation for the following and find the type of reaction in each case.
(a) Potassium bromide(aq) + Barium iodide(aq) equals Potassium iodide(aq) + Barium bromide(s)
(b) Zinc carbonate(s) equals Zinc oxide(s) + Carbon dioxide(g)
(c) Hydrogen(g) + Chlorine(g) equals Hydrogen chloride(g)
(d) Magnesium(s) + Hydrochloric acid(aq) equals Magnesium chloride(aq) + Hydrogen(g)

Q9. What does one mean by exothermic and endothermic reactions? Give examples.

Q10. Why is respiration considered an exothermic reaction? Explain.

Q11. Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

Q12. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

Q13. What is the difference between displacement and double displacement reactions? Write equations for these reactions.

Q14. In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

Q15. What do you mean by a precipitation reaction? Explain by giving examples.

Q16. Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction

Q17. A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

Q18. Why do we apply paint on iron articles?

Q19. Oil and fat having food items are flushed with nitrogen. Why?

Q20. Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity