Chapter 1 

Chemical Reactions And Equations 

ā§°াāϏাāϝ়āύিāĻ• āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া āφ⧰ু āϏāĻŽীāϕ⧰āĻŖ 


EXERCISES

āĻŦ্āϝাāϝ়াāĻŽ


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

 1. āϤāϞ⧰ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াā§° āĻŦিāώāϝ়ে āĻ•োāύāϟো āĻŽāύ্āϤāĻŦ্āϝ āĻ…āĻļুāĻĻ্āϧ? 

 2PbO(s) + C(s) → 2Pb(s) + CO2(g)

2āĻĒিāĻŦিāĻ“(āĻŦোā§°) + āϚি(āĻŦোā§°) → 2āĻĒিāĻŦি(āĻŦোā§°) + āϚি.āĻ“.2(āϜি)

 (a) Lead is getting reduced.

 (āĻ•) āϏীāĻš āĻš্ā§°াāϏ āĻšৈ āφāĻšিāĻ›ে।

 Ans-

(b) Carbon dioxide is getting oxidised.

(āĻ–) āĻ•াā§°্āĻŦāύ āĻĄাāχ āĻ…āĻ•্āϏাāχāĻĄ āϜাā§°āĻŖ āĻšৈ āφāĻ›ে।

  Ans-

(c) Carbon is getting oxidised.

(āĻ—) āĻ•াā§°্āĻŦāύ āĻ…āĻ•্āϏিāĻĄাāχāϜ āĻšৈ āφāĻ›ে।

  Ans-

(d) Lead oxide is getting reduced.

(āϘ) āϞীāĻĄ āĻ…āĻ•্āϏাāχāĻĄ āĻš্ā§°াāϏ āĻšৈ āφāĻšিāĻ›ে।

Ans-

 (i) (a) and (b)

 āĻ•) (āĻ•) āφ⧰ু (āĻ–)

Ans-

(ii) (a) and (c)

(āĻ–) (āĻ•) āφ⧰ু (āĻ—)

Ans-

(iii)  (a), (b) and (c)

(āĻ—) (āĻ•), (āĻ–) āφ⧰ু (āĻ—)

Ans-

(iv) all

(āϘ) āϏāĻ•āϞো

Ans-

2. Fe,O,+2A1 → Al,0, + 2Fe

2. āĻĢে, āĻ“,+2āĻ1 → āφāϞ,0, + 2āĻĢে

 The above reaction is an example of a

 āĻ“āĻĒā§°োāĻ•্āϤ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াāϟো āĻāϟা ā§° āωāĻĻাāĻšā§°āĻŖ

 (a) combination reaction.

 (āĻ•) āϏংāĻŽিāĻļ্ā§°āĻŖ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া।

  Ans-

(b) double displacement reaction.

(āĻ–) āĻĻ্āĻŦৈāϤ āϏ্āĻĨাāύāϚ্āϝুāϤি āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া।

  Ans-

(c) decomposition reaction.

(āĻ—) āĻĒāϚāύ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া।

 Ans-

 (d) displacement reaction.

 (āϘ) āϏ্āĻĨাāύāϚ্āϝুāϤি āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া।

  Ans-

3. What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. (a) Hydrogen gas and iron chloride are produced.

3. āϞোā§° āĻ­ā§°্āϤিāϤ āĻĒাāϤāϞ āĻšাāχāĻĄ্ā§°āĻ•্āϞ'ā§°িāĻ• āĻāϚিāĻĄ āϝোāĻ— āϕ⧰িāϞে āĻ•ি āĻšāϝ়? āϏāĻ িāĻ• āωāϤ্āϤ⧰āϟো āϟিāĻ• āϕ⧰āĻ•। (āĻ•) āĻšাāχāĻĄ্ā§°āϜেāύ āĻ—েāĻ› āφ⧰ু āϞোā§° āĻ•্āϞ⧰াāχāĻĄ āĻ‰ā§ŽāĻĒāύ্āύ āĻšāϝ়।

  Ans-

(b) Chlorine gas and iron hydroxide are produced.

(āĻ–) āĻ•্āϞোā§°িāύ āĻ—েāĻ› āφ⧰ু āϞোāĻšাāχāĻĄ্ā§°āĻ•্āϏাāχāĻĄ āĻ‰ā§ŽāĻĒাāĻĻāύ āϕ⧰া āĻšāϝ়।

  Ans-

(c) No reaction takes place.

(āĻ—) āĻ•োāύো āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া āύāĻšāϝ়।

  Ans-

(d) Iron salt and water are produced.

(āϘ) āϞো āύিāĻŽāĻ– āφ⧰ু āĻĒাāύী āĻ‰ā§ŽāĻĒাāĻĻāύ āϕ⧰া āĻšāϝ়।

  Ans-

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

4. āĻāĻ• āϏāύ্āϤুāϞিāϤ ā§°াāϏাāϝ়āύিāĻ• āϏāĻŽীāϕ⧰āĻŖ āĻ•ি? ā§°াāϏাāϝ়āύিāĻ• āϏāĻŽীāϕ⧰āĻŖāĻŦোā§° āĻ•িāϝ় āϏāύ্āϤুāϞিāϤ āϕ⧰িāĻŦ āϞাāĻ—ে?

  Ans-

5. Translate the following statements into chemical equations and then balance them.

5. āύিāĻŽ্āύāϞিāĻ–িāϤ āĻŽāύ্āϤāĻŦ্āϝāĻŦোā§° ā§°াāϏাāϝ়āύিāĻ• āϏāĻŽীāϕ⧰āĻŖāϞৈ āĻ…āύুāĻŦাāĻĻ āϕ⧰āĻ• āφ⧰ু āϤাā§° āĻĒিāĻ›āϤ āϏেāχāĻŦোā§° āϏāύ্āϤুāϞিāϤ āϕ⧰āĻ•।

(a) Hydrogen gas combines with nitrogen to form ammonia.

(āĻ•) āĻšাāχāĻĄ্ā§°āϜেāύ āĻ—েāĻ› āύাāχāϟ্ā§°āϜেāύ⧰ āϏৈāϤে āĻŽিāĻšāϞি āĻšৈ āĻāĻŽোāύিāϝ়া āĻ—āĻ āύ āϕ⧰ে।

 Ans-

 (b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.

 (āĻ–) āĻĒাāύী āφ⧰ু āĻ›াāϞāĻĒুā§° āĻĄাāχ āĻ…āĻ•্āϏাāχāĻĄ āĻĻিāĻŦāϞৈ āĻšাāχāĻĄ্ā§°āϜেāύ āĻ›াāϞāĻĢাāχāĻĄ āĻ—েāĻ› āĻŦাāϝ়ুāϤ āϜ্āĻŦāϞে।

  Ans-

(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

(āĻ—) āĻŦেā§°িāϝ়াāĻŽ āĻ•্āϞ⧰াāχāĻĄে āĻāϞুāĻŽিāύিāϝ়াāĻŽ āĻ›াāϞāĻĢেāϟ⧰ āϏৈāϤে āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া āϕ⧰ি āĻāϞুāĻŽিāύিāϝ়াāĻŽ āĻ•্āϞ⧰াāχāĻĄ āφ⧰ু āĻŦেā§°িāϝ়াāĻŽ āĻ›াāϞāĻĢেāϟ⧰ āĻ…ā§ąāĻ•্āώāϝ় āĻĒ্ā§°āĻĻাāύ āϕ⧰ে।

Ans-

(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

(āϘ) āĻĒāϟাāĻ›িāϝ়াāĻŽ āϧাāϤুāχ āĻĒাāύীā§° āϏৈāϤে āĻŦিāĻ•্ā§°িāϝ়া āϕ⧰ি āĻĒāϟাāĻ›িāϝ়াāĻŽ āĻšাāχāĻĄ্ā§°āĻ•্āϏাāχāĻĄ āφ⧰ু āĻšাāχāĻĄ্ā§°āϜেāύ āĻ—েāĻ› āĻĒ্ā§°āĻĻাāύ āϕ⧰ে।

  Ans-

6. Balance the following chemical equations.

6. āύিāĻŽ্āύāϞিāĻ–িāϤ ā§°াāϏাāϝ়āύিāĻ• āϏāĻŽীāϕ⧰āĻŖāĻŦোā§° āϏāύ্āϤুāϞিāϤ āϕ⧰āĻ•।

 (a) HNO, +Ca(OH),→ Ca(NO3)2 + H₂O

 (āĻ•) āĻāχāϚāĻāύāĻ“, +āĻ•ে(āĻ“āĻāχāϚ), → āĻ•ে(āĻāύāĻ“3)2 + āĻāχāϚ₂āĻ“ 

  Ans-

(b) NaOH + H₂SO,→ Na₂SO, +H₂O (c) NaCl + AgNO,→ AgCl + NaNO,

(āĻ–) āύাāĻ“āĻš + āĻāχāϚ₂āĻāĻ›āĻ“,→ āύা₂āĻāĻ›āĻ“, +āĻāχāϚ₂āĻ“ (āĻ—) āĻāύāĻāϚিāĻāϞ + āĻāϜিāĻāύāĻ…', → āĻāϜিāϚিāĻāϞ + āύাāύো,

  Ans-

(d) BaCl2 + H₂SO → BaSO, + HCl

(āϘ) āĻŦিāĻāϚিāĻāϞ2 + āĻāχāϚ₂āĻāĻ›āĻ…' → āĻŦিāĻāĻāĻ›āĻ“, + āĻāχāϚāϚিāĻāϞ

  Ans-

7. Write the balanced chemical equations for the following reactions.

7. āύিāĻŽ্āύāϞিāĻ–িāϤ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াāĻŦোā§°ā§° āĻŦাāĻŦে āϏāύ্āϤুāϞিāϤ ā§°াāϏাāϝ়āύিāĻ• āϏāĻŽীāϕ⧰āĻŖāĻŦোā§° āϞিāĻ–āĻ•।

 (a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

 (āĻ•) āĻ•েāϞāϚিāϝ়াāĻŽ āĻšাāχāĻĄ্ā§°āĻ•্āϏাāχāĻĄ + āĻ•াā§°্āĻŦāύ āĻĄাāχ āĻ…āĻ•্āϏাāχāĻĄ → āĻ•েāϞāϚিāϝ়াāĻŽ āĻ•াā§°্āĻŦāύেāϟ + āĻĒাāύী

  Ans-

(b) Zinc+ Silver nitrate → Zinc nitrate + Silver

(āĻ–) āϜিংāĻ•+ āϚিāϞāĻ­াā§° āύাāχāϟ্ā§°েāϟ → āϜিংāĻ• āύাāχāϟ্ā§°েāϟ + ā§°ূāĻĒাāϞী

  Ans-

(c) Aluminium + Copper chloride → Aluminium chloride + Copper

(āĻ—) āĻāϞুāĻŽিāύিāϝ়াāĻŽ + āĻ•āĻĒাā§° āĻ•্āϞ⧰াāχāĻĄ → āĻāϞুāĻŽিāύিāϝ়াāĻŽ āĻ•্āϞ⧰াāχāĻĄ + āϤাāĻŽ

  Ans-

(d) Barium chloride + Potassium sulphate→ Barium sulphate + Potassium chloride

(āϘ) āĻŦেā§°িāϝ়াāĻŽ āĻ•্āϞ⧰াāχāĻĄ + āĻĒāϟাāĻ›িāϝ়াāĻŽ āĻ›াāϞāĻĢেāϟ→ āĻŦেā§°িāϝ়াāĻŽ āĻ›াāϞāĻĢেāϟ + āĻĒāϟাāĻ›িāϝ়াāĻŽ āĻ•্āϞ⧰াāχāĻĄ

  Ans-

8. Write the balanced chemical equation for the following and identify the type of reaction in each case.

8. āύিāĻŽ্āύāϞিāĻ–িāϤāĻŦোā§°ā§° āĻŦাāĻŦে āϏāύ্āϤুāϞিāϤ ā§°াāϏাāϝ়āύিāĻ• āϏāĻŽীāϕ⧰āĻŖ āϞিāĻ–āĻ• āφ⧰ু āĻĒ্ā§°āϤিāϟো āĻ•্āώেāϤ্ā§°āϤ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াā§° āĻĒ্ā§°āĻ•াā§° āϚিāύাāĻ•্āϤ āϕ⧰āĻ•।

(a) Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)

(āĻ•) āĻĒāϟাāĻ›িāϝ়াāĻŽ āĻŦ্ā§°āĻŽাāχāĻĄ (āĻāĻ•) + āĻŦেā§°িāϝ়াāĻŽ āφāϝ়োāĻĄাāχāĻĄ (āĻāĻ•) → āĻĒāϟাāĻ›িāϝ়াāĻŽ āφāϝ়োāĻĄাāχāĻĄ (āĻāĻ•) + āĻŦেā§°িāϝ়াāĻŽ āĻŦ্ā§°āĻŽাāχāĻĄ(āĻŦোā§°)

  Ans-

(b) Zinc carbonate(s) →→ Zinc oxide(s) + Carbon dioxide(g)

(āĻ–) āϜিংāĻ• āĻ•াā§°্āĻŦāύেāϟ(āĻŦোā§°) →→ āϜিংāĻ• āĻ…āĻ•্āϏাāχāĻĄ (āĻŦোā§°) + āĻ•াā§°্āĻŦāύ āĻĄাāχ āĻ…āĻ•্āϏাāχāĻĄ (āϜি)

   Ans-

(c) Hydrogen(g) + Chlorine(g) → Hydrogen chloride(g) 

(āĻ—) āĻšাāχāĻĄ্ā§°āϜেāύ (āĻ—্ā§°াāĻŽ) + āĻ•্āϞোā§°িāύ (āĻ—্ā§°াāĻŽ) → āĻšাāχāĻĄ্ā§°āϜেāύ āĻ•্āϞ⧰াāχāĻĄ (āϜি) 

  Ans-

(d) Magnesium(s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g)

(āϘ) āĻŽেāĻ—āύেāĻ›িāϝ়াāĻŽ (āĻŦোā§°) + āĻšাāχāĻĄ্ā§°āĻ•্āϞ'ā§°িāĻ• āĻāϚিāĻĄ (āĻāĻ•িāω) → āĻŽেāĻ—āύেāĻ›িāϝ়াāĻŽ āĻ•্āϞ⧰াāχāĻĄ (āĻāĻ•) + āĻšাāχāĻĄ্ā§°āϜেāύ(āϜি)

   Ans-

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

9. āĻāĻ•্āϏোāĻĨাā§°্āĻŽিāĻ• āφ⧰ু āĻāĻŖ্āĻĄোāĻĨাā§°্āĻŽিāĻ• āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াā§° āĻ…ā§°্āĻĨ āĻ•ি? āωāĻĻাāĻšā§°āĻŖ āĻĻিāϝ়āĻ•।

   Ans-

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

ā§§ā§Ļ. āĻļ্āĻŦāϏāύāĻ• āĻ•িāϝ় āĻāĻ• āωāϚ্āĻ›ৃংāĻ–āϞ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়া āĻŦুāϞি āĻ—āĻŖ্āϝ āϕ⧰া āĻšāϝ়? āĻŦ্āϝাāĻ–্āϝা āϕ⧰āĻ•।

   Ans-

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

ā§§ā§§. āĻĒāϚāύ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াāĻ• āĻ•িāϝ় āϏংāĻŽিāĻļ্ā§°āĻŖ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াā§° āĻŦিāĻĒā§°ীāϤ āĻŦুāϞি āĻ•োā§ąা āĻšāϝ়? āĻāχ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াāĻŦোā§°ā§° āĻŦাāĻŦে āϏāĻŽীāϕ⧰āĻŖ āϞিāĻ–āĻ•।

  Ans-

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

12. āĻĒāϚāύ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াā§° āĻŦাāĻŦে āĻāϟা āĻ•ৈ āϏāĻŽীāϕ⧰āĻŖ āϞিāĻ–āĻ• āϝ'āϤ āϤাāĻĒ, āĻĒোāĻšā§° āĻŦা āĻŦিāĻĻ্āϝুāϤ⧰ ā§°ূāĻĒāϤ āĻļāĻ•্āϤি āϝোāĻ—াāύ āϧ⧰া āĻšāϝ়।

 Ans-

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

13. āϏ্āĻĨাāύāϚ্āϝুāϤি āφ⧰ু āĻĻ্āĻŦৈāϤ āϏ্āĻĨাāύাāύ্āϤ⧰ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াā§° āĻŽাāϜāϤ āĻĒাā§°্āĻĨāĻ•্āϝ āĻ•ি? āĻāχ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াāĻŦোā§°ā§° āĻŦাāĻŦে āϏāĻŽীāϕ⧰āĻŖ āϞিāĻ–āĻ•।

 Ans-

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

14. ā§°ূāĻĒā§° āĻļোāϧāύāϤ, ā§°ূāĻĒাāϞী āύাāχāϟ্ā§°েāϟ āĻĻ্ā§°ā§ąāĻŖā§° āĻĒā§°া ā§°ূāĻĒ āĻĒুāύ⧰ুāĻĻ্āϧাā§°āϤ āϤাāĻŽāϧাāϤুā§° āĻĻ্āĻŦাā§°া āϏ্āĻĨাāύাāύ্āϤ⧰ āĻ…āύ্āϤ⧰্āĻ­ুāĻ•্āϤ āφāĻ›িāϞ। āĻ…āύ্āϤ⧰্āĻ­ুāĻ•্āϤ āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াāϟো āϞিāĻ–āĻ•। 

  Ans-

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

ā§§ā§Ģ. āĻŦā§°āώুāĻŖā§° āĻĒ্ā§°āϤিāĻ•্ā§°িāϝ়াā§° āĻ…ā§°্āĻĨ āĻ•ি? āωāĻĻাāĻšā§°āĻŖ āĻĻি āĻŦā§°্āĻŖāύা āϕ⧰āĻ•।

   Ans-

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

16. āĻĻুāϟা āĻ•ৈ āωāĻĻাāĻšā§°āĻŖā§° āϏৈāϤে āĻ…āĻ•্āϏিāϜেāύ āϞাāĻ­ āĻŦা āĻ•্āώāϤিā§° āĻ•্āώেāϤ্ā§°āϤ āύিāĻŽ্āύāϞিāĻ–িāϤāĻŦোā§° āĻŦā§°্āĻŖāύা āϕ⧰āĻ•।

 (a) Oxidation

 (āĻ•) āϜাā§°āĻŖ

  Ans-

 (b) Reduction

 (āĻ–) āĻš্ā§°াāϏ

   Ans-

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.

17. āĻŦāϤাāĻšāϤ āĻ—ā§°āĻŽ āϕ⧰াā§° āϏāĻŽāϝ়āϤ āĻāϟা āϚāĻ•āϚāĻ•ে āĻŽুāĻ—া ā§°āϙ⧰ āωāĻĒাāĻĻাāύ āĻāĻ•্āϏ āĻ•'āϞা ā§°āϙ⧰ āĻšৈ āĻĒā§°ে। 'āĻāĻ•্āϏ' āωāĻĒাāĻĻাāύāφ⧰ু āĻ—āĻ āύ āĻšোā§ąা āĻ•'āϞা ā§°āϙ⧰ āϝৌāĻ—āϟোā§° āύাāĻŽ āĻĻিāϝ়āĻ•।

   Ans-

18. Why do we apply paint on iron articles?

ā§§ā§Ž. āφāĻŽি āϞোā§° āϏাāĻŽāĻ—্ā§°ীā§° āĻ“āĻĒā§°āϤ ā§°ং āĻ•িāϝ় āĻĒ্ā§°āϝ়োāĻ— āϕ⧰োঁ?

   Ans-

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

19. āĻ–াāĻĻ্āϝ āϏাāĻŽāĻ—্ā§°ী āĻĨāĻ•া āϤেāϞ āφ⧰ু āϚ⧰্āĻŦি āύাāχāϟ্ā§°āϜেāύ⧰ āĻĻ্āĻŦাā§°া āĻĢ্āϞাāĻļ āϕ⧰া āĻšāϝ়। āĻ•িāϝ়?

 Ans-

20. Explain the following terms with one example each.

20. āĻĒ্ā§°āϤিāϟো āωāĻĻাāĻšā§°āĻŖেā§°ে āύিāĻŽ্āύāϞিāĻ–িāϤ āĻļāĻŦ্āĻĻāĻŦোā§° āĻŦā§°্āĻŖāύা āϕ⧰āĻ•।

 (a) Corrosion

 (āĻ•) āĻ•্āώāϝ়

Ans-

(b) Rancidity

(āĻ–) ā§°েāύāϚিāĻĄিāϟি

   Ans-


 Jit bora Question type.