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## CHEMICAL REACTION AND EQUATIONS:-

1. Which of the following metals can replace copper from a solution of copper sulphate?

[HSLC 2015]

(a) Silver.

(b) Gold.

(c) Zinc.

(d) Mercury.

Ans.:- (c) Zinc.

2. $Fe_{2}O_{3}&space;\;+&space;\;&space;2Al&space;\;&space;\rightarrow&space;\;&space;Al_{2}O_{3}\;&space;+&space;\;&space;2Fe$
The above reaction is an example of:-                              [HSLC 2016]
(a) a combination reaction.

(b) a decomposition reaction.

(c) a displacement reaction.

(d) a double displacement reaction.

Ans.:- (c) a displacement reaction.

3. (a) Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions?       [HSLC 2015]

Ans.:- In a decomposition reaction, a single reactant breaks down to give simpler products. On the other hand, when a single product is formed from two or more reactants that reaction is known as combination reactions. Thus both reactions are opposite to each other.
Example of decomposition reaction:-

$CaCO_{3}&space;(s)&space;\xrightarrow[]{Heat}\;&space;CaO(s)&space;\;&space;+&space;\;&space;CO_{2}(g)$ example of a combination reaction:-

$C(s)\;+\;O_{2}(g)&space;\rightarrow&space;CO_{2}(g)$

(b) Write the balanced equation for the following chemical reactions.

(i) Hydrogen + Chlorine → Hydrogen chloride

Ans.:- $H_{2}\;+\;Cl_{2}\;\rightarrow\;2HCl$

(ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride

Ans.:- $BaCl_{2}\;+\;Al_{2}(SO_{4})_{3}\;\rightarrow\;AlCl_{3}\;+\;BaSO_{4}$

(iii) Sodium + Water → Sodium hydroxide + Hydrogen

Ans.:- $Na&space;\;+\;H_{2}O\;\rightarrow\;NaOH\;+\;H_{2}$

4. Take 2 g of silver chloride in a china dish and place it in sunlight.

(a) What is the colour of silver chloride after some time?

Ans.:- After some time, Silver chloride turns grey in sunlight.

(b) What type of reaction takes place?

Ans.:- Decomposition reaction.

(c) Write the chemical reaction for the above observation.

Ans.:- $2AgCl(s)&space;\xrightarrow[]{sunlight}\;2Ag(s)\;+\;Cl_{2}(g)$

5. Translate the following statements into chemical equations and balance them:-    [HSLC 2015 ]

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

Ans.:- $BaCl_{2}&space;\;+\;Al_{2}(SO_{4})_{3}\;\rightarrow\;AlCl_{3}\;+\;BaSO_{4}$

After balancing it,

$3BaCl_{2}&space;\;+\;Al_{2}(SO_{4})_{3}\;\rightarrow\;2AlCl_{3}\;+\;3BaSO_{4}$

(b) Zinc reacts with copper sulphate to give zinc sulphate and metallic copper.

Ans.:- $Zn\;+\;CuSO_{4}\rightarrow\;ZnSO_{4}\;+\;Cu$

(c) Hydrogen sulphide burns in air to give water and sulphur dioxide.

Ans.:-$H_{2}S\;+\;O_{2}\;\rightarrow\;H_{2}O\;+\;SO_{2}$

6. Translate the following statements into chemical equations and balance them:-

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

Ans.:-$3H_{2}\;+\;N_{2}\;\rightarrow\;2NH_{3}$

(b) Zinc carbonate is heated strongly to give zinc oxide and carbon dioxide.

Ans.:-$ZnCO_{3}&space;\;\rightarrow\;ZnO\;+\;CO_{2}$

7. Take 1g copper powder in a china dish and heat, then-      [HSLC 2016]

(a) What will be the colour of the copper powder?

Ans.:- The colour of the copper powder becomes black due to the formation of CuO.

(b) Write the balanced chemical reaction for the above observation.

Ans.:- $2Cu&space;\;+\;O_{2}\rightarrow&space;\;2CuO$

8. Define exothermic endothermic reaction.

Ans.:- Exothermic reaction:- The reaction in which heat is evolved is called exothermic reaction. E.g. burning of coke in presence of air.

$2C(s)\;+\;O_{2}(g)\;\rightarrow\;2CO(g)\;+\;heat$

Endothermic reaction:- The reaction in which heat is absorbed is called exothermic reaction. E.g. combination of to$N_{2}\;&space;and\;&space;O_{2}&space;\;$ form nitric oxide.

$N_{2}\;+\;O_{2}\;+\;heat\;\rightarrow\;2NO(g)$

9. Which one of the following is not a chemical change-

(a) Burning of candle wax.

(b) Evaporation of water.

(c) Digesting of food in our body.

(d) Cooking of food.

Ans.:- (b) Evaporation of water.

10. $Fe_{2}O_{3}\;+\;2Al\;\rightarrow\;Al_{2}O_{3}\;+\;2Fe,$ This reaction is an example of –

(a) displacement reaction.

(b) decomposition reaction.

(c) double displacement reaction.

(d) combination reaction.

Ans.:- (a) displacement reaction.

11. What happens when dilute hydrochloric acid is added to iron filings? Choose the
(a) Iron salt and water are produced.
(b) No reaction takes place.
(c) Chlorine gas and iron hydroxide are produced.
(d) Hydrogen gas and iron chloride are produced.

Ans.:- (d) Hydrogen gas and iron chloride are produced.

12. Which of the following is not a physical change-
(a) Melting of ice to give water.
(b) Dissolution of salt in the air.
(c) combustion of Liquefied petroleum gas (LPG).
(d) Boiling of water to give water vapour.

Ans.:- (c) combustion of Liquefied petroleum gas (LPG)

13. Which of the following are combination reactions?
.
$(1)&space;\;Zn\;+\;FeSO_{4}\;\rightarrow\;ZnSO_{4}\;+Fe$$(2)&space;\;4Al\;+\;3O_{2}\;\rightarrow\;2Al_{2}O_{3}$$(3)&space;\;MgO\;+\;H_{2}O\;\rightarrow\;Mg(OH)_{2}$$(4)&space;\;2KClO_{3}\;\rightarrow\;2KCl\;+\;3O_{2}$

(a) (4) and (2)             (b) (2) and (1)

(c) (3) and (1)              (d (3) and (2)

Ans.:- (d (3) and (2)

14. Which of the following is an endothermic process

(1) Dilution of sulphuric acid.
(2) Sublimation of dry ice.
(3) Condensation of water vapour.
(4) Evaporation of water vapour.

(a) (1) and (3)              (b) (2) only
(c) (3) only                    (d) (2) and (4)

Ans.:-  (d) (2) and (4).

15. Which one of the following processes involve chemical reactions:-

(a) Liquefaction of air.

(b) Keeping petrol in a china dish in the open.

(c) Heating copper wire in presence of air at high temperature.

(d) Storing of oxygen gas under pressure in a gas cylinder.

Ans.:- (c) Heating copper wire in presence of air at high temperature.

16. Which of the following are exothermic processes?

(1) Dilution of an acid.

(2) Evaporation of water

(3) Sublimation of camphor

(4) The reaction of water with quicklime.

(a) (4) and (1)            (b) (1) and (2)
(c) (4) and (3)             (d) (2) and (3)

Ans.:- (a) (4) and (1) .

17. $4NH_{3}(g)\;+\;5O_{2}(g)\;\rightarrow\;4NO(g)\;+\;6H_{2}O(g)$This reaction is an example of

(1) displacement reaction.
(2) combination reaction.
(3) redox reaction.
(4) Neutralization reaction.

(a) (1) and (4)            (b) (2) and (3)
(c) (1) and (3)            (d) (3) and (4)

Ans.:- (c) (1) and (3).

18. Which of the following gases can be used for storage of a fresh sample of an oil for a long time?
(a) Helium or nitrogen.
(b) Carbon dioxide or helium.
(c) Nitrogen or oxygen.
(d) Carbon dioxide or oxygen.

Ans.:- (a) Helium or nitrogen.

19. The reaction of lime with water is a-

(a) decomposition reaction.
(b) displacement reaction.
(c) double displacement reaction.
(d) combination reaction.

Ans.:- (d) combination reaction.

20. Strong heating of copper sulphate gives a residue of –

(a) $CuO$          (b)$Cu_{2}O$

(c) Neither $Cu_{2}O$ and $CuO$(d) both $Cu_{2}O$ and $CuO$

Ans.:- (b)$Cu_{2}O$

21. When magnesium ribbon s burnt in air and the ash is collected in a china dish. It contains-
(a) Magnesium nitride only       (b) Magnesium oxide only
(c) Magnesium oxide and magnesium carbide     (d) both magnesium oxide and magnesium nitride.

Ans:- (b) Magnesium oxide only

22. Which one of the following should not be done

(a) Placing dilute sulphuric acid in a copper vessel.

(b) Placing zinc sulphate solution in a copper vessel.

(c) Placing copper sulphate solution in a silver vessel.

(d)  Placing dilute sulphuric acid in a zinc vessel.

Ans.:- (d)  Placing dilute sulphuric acid in a zinc vessel.

23. The reaction of zinc with dilute sulphuric acid is –

(a) a displacement as well as a redox reaction.

(b) a decomposition reaction as well as combination reaction.

(c) a redox reaction as well as a double displacement reaction.

d) a precipitation reaction as well as a double redox reaction.

Ans.:- (a) a displacement as well as a redox reaction.

24. When iron nails are kept in copper sulphate solution for 2-3 hours and then
taken out and washed. The colour of iron nails be-
(a) Red         (b) brown
(c) black       (d) grey

Ans.:-(d)grey

25. Which of the following statements is not correct when barium chloride solution is mixed with sodium sulphate solution-
(a) It is a redox reaction          (b) It is a fast reaction
(c) It is a double displacement reaction          (d) It is a precipitation reaction.

Ans.:- (a)It is a redox reaction.

26. Which of the following is a displacement reaction-

(a)$MgCO_{3}&space;\rightarrow&space;MgO&space;+&space;CO_{2}$

(b)$2Na&space;+&space;2H_{2}O&space;\rightarrow&space;2NaOH&space;+&space;H_{2}$

(c) $2H_{2}&space;+&space;O_{2}&space;\rightarrow&space;2H_{2}O$

(d) $2Pb(NO_{3})_{2}&space;\rightarrow&space;2PbO&space;+&space;4NO_{2}&space;+&space;O_{2}$

Ans.:- (b) $2Na&space;+&space;2H_{2}O&space;\rightarrow&space;2NaOH&space;+&space;H_{2}$

27. Oxidation is a process which involves-

(a) removal of hydrogen.

(c) removal of oxygen.

(i) (b) and (c)        (ii) (a) and (b)

(iii) (a) and (d)      (iv) (b) and (d)

Ans.:- (ii) (a) and (b)

28. Reduction involves-

(b) removal of hydrogen

(d) removal of oxygen.

(i) (b) and (c)        (ii) (a) and (b)

(iii) (c) and (d)      (iv) (b) and (d)

Ans.:- (iii) (c) and (d).

29.  when Ag is exposed to air it gets a black coating of

$(a)&space;\;AgNO_{3}\;\;\;\;(b)\;Ag_{2}S$$(c)\;&space;Ag_{2}CO_{3}\;\;\;\;(d)\;Ag_{2}O$

Ans.:- $(b)\;Ag_{2}S$

30. What type of chemical reaction takes place when electricity is passed through water?
(a) Double displacement.
(b) Combination.
(c) Displacement.
(d) Decomposition.

Ans.:- (d) Decomposition.

31. The condition produced by aerial Oxidation of fats and oils in foods marked by Unpleasant smell and taste is called
(a) reduction

(b) corrosion

(c) rancidity

(d) antioxidants

Ans.:- (c) rancidity

32. When green coloured ferrous sulphate crystals are heated, the colour of the crystals changes because –

(a) It loses water of crystallisation.

(b) It is decomposed to ferric oxide.

(c) It forms.$SO_{2}$

(d) It forms.$SO_{3}$

33. Which of the following are combination reactions?

$(1)&space;\;2KClO_{3}\;\xrightarrow[]{\;Heat&space;\;}\;2KCl\;+\;3O_{2}$$(2)\;MgO\;+\;H_{2}O\;\rightarrow\;Mg(OH)_{2}$$(3)\;Zn\;+\;&space;FeSO_{4}\;\rightarrow\;ZnSO_{4}\;+\;Fe$$(4)\;4Al\;+\;3O_{2}\;\rightarrow\;2Al_{2}O_{3}$(a) (1) and (3)          (b) (3) and (4)

(c) (2) and (3)          (d) (2) and (4)

Ans.:-  (d) (2) and (4)

34. Which among the following changes are exothermic or endothermic in nature?

(a) Decomposition of ferrous sulphate.

(b) Dilution of sulphuric acid.

(c) Dissolution of sodium hydroxide in water.

(d) Dissolution of ammonium chloride in water.

Ans.:- (a) Decomposition of ferrous sulphate.

35. Electrolysis of water is-

(a) decomposition reaction.
(b) displacement reaction.
(c) double displacement reaction.
(d) combination reaction.

Ans.:- (a) decomposition reaction.

36. Fill in the blanks:( With Answers)

(i)   Corrosion is the process in which metals are eaten up gradually by the action of air, moisture or a chemical on their surface.

(ii) Precipitation reactions produce the insoluble compound.

(iii) A complete chemical equation represents the reactants, products and their physical states

(iv) The addition of hydrogen to a substance is called reduction whereas removal of hydrogen is called oxidation.

(v) The addition of oxygen to a substance is called oxidation whereas removal of oxygen is called reduction.

(vi) In a combination reaction, two or more substances combine to form a new single substance.

(vii) $Zn(s)\;+\;H_{2}SO_{4}(aq)\;\rightarrow\;ZnSO_{4}&space;(\;\underline{\;aq\;}\;)\;+\;H_{2}(\;\underline{\;g\;})$

(viii) $Ca(OH)_{2}\;+\;\underline{\;CO_{2}\;}\;\rightarrow\;CaCO_{3}\;+\;H_{2}O$

(ix) $Na_{2}SO_{4}\;+\;BaCl_{2}\;\rightarrow\;\underline{\;BaSO_{4}\;}\;+\;2NaCl.$

(x) $Pb(NO_{3})_{2}&space;(aq)\;+\;2Kl(aq)\;\rightarrow\;Pbl_{2}(\;\underline{\;s\;}\;)\;+\;2KnO_{3}(\;\underline{\;aq\;}\;)$

(xi) Reactions in which energy is given out are known as exothermic.

(xii) Reactions in which energy is absorbed are known as endothermic.

37. Determine true or false

(a) The green coating on copper is due to the formation of basic Copper carbonate.

Ans.:- True.

(b) Zine and lead are less reactive metal than copper.

Ans:- False

(c) Calcium oxide is known as lime water.

Ans.:- False.

(d) When an element displaces another element from its compound, a double dis-
placement reaction occurs.

Ans:- True

(e) $2H_{2}O\;+\;Heat\;\rightarrow&space;2H_{2}\;&space;+&space;O_{2}$ is an example of an exothermic reaction.

Ans:- False

38. What do you mean by a balanced equation?

Ans:- A chemical equation is said to be balanced when the numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation.

39. The arrow pointing downwards(↓) along with a product represents ——- whereas the arrow pointing upwards (↓) represents ———.

Ans:- The arrow pointing downwards(↓) along with a product represents precipitate whereas the arrow pointing upwards (↓) represents a gaseous product.

40. Why is hydrogen peroxide kept in a coloured bottle?

Ans:- Hydrogen peroxide is a highly reactive metal. It can react with light or heat to produce water. To prevent it’s reaction with light and heat to make water it is stored in coloured bottles so that light can not pass through it.

41. What do you mean by activity series of metals?

Ans:- The activity series of metals is a list of metals ranked in order of decreasing reactivity to displace hydrogen gas from water and acid solutions. It can also be used to predict which metals will displace other metals in aqueous solutions.

42. Name the most reactive metals and least reactive metals of the activity series, of metals.

Ans:- the most reactive metals- Potassium

the least reactive metal- Gold.

43. Why is hydrogen included in the activity series of metals?

Ans:- Hydrogen is included in the reactivity series of metals because of its property of electropositivity i. e. Losing electron to form a positive ion.

44. What is an oxidizing agent?

Ans:- An oxidizing agent, or oxidantgains electrons and is reduced in a chemical reaction. Also known as the electron acceptor. Examples of oxidizing agents include halogens, potassium nitrate, and nitric acid.

45. What is a reducing agent?

Ans:- A reducing agent, or reductantloses electrons and is oxidized in a chemical reaction. A reducing agent is known as the electron donor.

46. What are two necessary conditions for rusting of an iron article?

Ans:- The two essential conditions of rusting iron article are the presence of oxygen, and the presence of water whose PH level is slightly acidic.

47. What do you mean by rancidity?

Ans:- When an oily or fatty substance is kept outside for a long time it gets
oxidised. As a result, its smell, taste etc, are completely changed and becomes uneatable
this process is called rancidity.

48. Write the type of reaction in the following-
(i) A reaction between an acid and base.
(ii) Rusting of iron.

Ans:- (I) Neutralisation reaction.

(II) Oxidation reaction.

(rusting of iron—— $4Fe\;+\;3O_{2}\;+\;6H_{2}O&space;\;\rightarrow\;4Fe(OH)&space;_{3}$)

49. Why do gold and silver not corrode in moist air?

Ans:-Gold and silver are the least reactive metals in the reactivity series, hence can not bond with oxygen easily. Therefore they both cannot get corroded easily.

50. What type of chemical reaction takes place, when-

(i) Sulphuric acid added into barium chloride solution.

Ans:- a double displacement reaction

$BaCl_{2}\;+H_{2}SO_{4}\;\rightarrow&space;BaSO_{4}\;+HCl$(ii) Limestone is heated

Ans:-Thermal decomposition reaction.

$CaCO_{3}\;\rightarrow&space;CaO\;+\;CO_{2}$(iii) Digestion of food occurs in the body.

Ans:- Exothermic reactions.

(iv) Electric current is passed through water

Ans:-Decomposition reaction.

(v) Zinc reacts with sulphuric acid to form zinc sulphate and hydrogen.

Ans:-a displacement reaction.     $Zn&space;+&space;H_{2}SO_{4}&space;\rightarrow&space;ZnSO_{4}&space;+H_{2}$

(vi) Ammonium and hydrogen chloride gases are mixed.

Ans:-Combination reaction.     $NH_{3}\;+HCl\rightarrow&space;NH_{4}Cl$

51. What is the chemical equation?

Ans:-Chemical Reaction is the transformation of a chemical substance into a new chemical substance by making and breaking of bonds between different atoms.

52. What happens when magnesium ribbons burn?

Ans:-When Magnesium burns in air, it reacts with oxygen present in air to form magnesium oxide.        $2Mg&space;+&space;O_{2}\rightarrow&space;2MgO$

53. Which substance is used for whitewashing the wall?

Ans:-Calcium Hydroxide (Slaked Lime).

54. What is the exothermic reaction? give one example.

Ans.:- Exothermic reaction:- The reaction in which heat is evolved is called exothermic reaction. E.g. burning of coke in presence of air.

$2C(s)\;+\;O_{2}(g)\;\rightarrow\;2CO(g)\;+\;heat$

55. What are  combination reaction write two chemical reaction

Ans:-When a single product is formed from two or more reactants is known as a combination reaction.

e.g.- $NH_{3}\;+HCl\rightarrow&space;NH_{4}Cl$   ;$2H_{2}&space;+&space;O_{2}&space;\rightarrow&space;2H_{2}O$

56. What is a decomposition reaction? Give example.

Ans:-In a decomposition reaction, a single reactant breaks down to give simpler products.

e.g. $CaCO_{3}&space;(s)&space;\xrightarrow[]{Heat}\;&space;CaO(s)&space;\;&space;+&space;\;&space;CO_{2}(g)$

57. What are displacement reactions? Give example.

Ans:- displacement reactions takes place when a more reactive metal displaces a less reactive metal.

$Zn&space;+&space;H_{2}SO_{4}&space;\rightarrow&space;ZnSO_{4}&space;+H_{2}$

58. What are double displacement reactions? Give example.

Ans:-The reactions in which there is an exchange of ions between the reactants are called double displacement reactions.

e.g. $Na_{2}SO_{4}\;+BaCl_{2}\;\rightarrow&space;BaSO_{4}\;+2NaCl$

59. What do you mean by precipitation reaction? Give example.

Ans:-precipitation reactions produce insoluble salts.

e.g. $Na_{2}SO_{4}\;+BaCl_{2}\;\rightarrow&space;BaSO_{4}\;+2NaCl$

60. What will happen when silver chloride is kept in sunlight?

Ans:- silver chloride turns grey in sunlight to form silver metal.

61. What will happen when lead nitrate powder is heated.

Ans:-Heating of lead nitrate emits brown fumes which are nitrogen dioxide.

62. Write a balanced chemical equation for each of the following reactions and also classify them.

a) Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water.

Ans:- Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water. [Hydrogen sulphide gas burns in air to give water and sulphur dioxide.]$2H_{2}S\;+\;3O_{2}\;\rightarrow&space;2H_{2}O\;+2SO_{2}$

b)A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.

Ans:- Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas.$2&space;C_{2}H_{5}OH\;+Na\rightarrow&space;2C_{2}H_{5}O^{-}Na^{+}\;&space;+&space;H_{2}$

C) Iron(III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.

Ans:- Iron (III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.$Fe_{2}O_{3}\;+3CO\;\rightarrow&space;\;2Fe\;+\;3CO_{2}$

d) Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.

Ans:-$Pb(CH_{3}COO)_{3}+\;2HCl\rightarrow&space;PbCl_{2}+\;CH_{3}COOH$

e) Phosphorus burns in oxygen to give phosphorus pentaoxide.

Ans:- $P_{4}+5O_{2}&space;\rightarrow&space;2P_{2}O_{5}$

F) Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.

Ans:- $BaCl_{2}+ZnSO_{4}&space;\rightarrow&space;ZnCl_{2}+BaSO_{4}$

G)Calcium hydroxide + carbon dioxide →calcium carbonate +water

Ans:- $Ca(OH)_{2}+CO_{2}&space;\rightarrow&space;CaCO_{3}+H_{2}O$

H) Aluminium +copper chloride ⇒Aluminium chloride+copper

Ans:- $2Al+3CuCl_{2}\rightarrow&space;2AlCl_{3}+3Cu$

I) an aqueous calcium hydroxide solution (limewater) reacts with carbon dioxide gas to produce a solid calcium carbonate precipitate and water.

Ans:- $Ca(OH)_{2}&space;+&space;CO_{2}\rightarrow&space;CaCO_{3}+H_{2}O$

Write the balanced chemical equations for the following reactions identify the type of reaction in each case-

a)Methane is burnt in the presence of oxygen to form carbon dioxide, water, and release heat and light.

Ans:- Methane is burnt in the presence of oxygen to form carbon dioxide, water, and release heat and light.

$CH_{4}\;+2O_{2}\overset{combustion}{\rightarrow}CO_{2}+H_{2}O+Heat+Light$

b) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas.

Ans:- $N_{2}+3H_{2}\rightarrow&space;2NH_{3}$

c) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.

Ans:- $CH_{3}COOH&space;+&space;NaOH\rightarrow&space;CH_{3}COONa+H_{2&space;}O$

d) Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated.$H_{2}SO_{4}$

Ans:- $CH_{3}COOH&space;+C_{2}H_{5}OH\;\overset{conc.h_{2}so_{4}}{\rightarrow}&space;\;\;CH_{3}COOC_{2}H_{5}+H_{2}O$

Write the balanced chemical equations for the following reactions:-

A)$Na+O_{2}\rightarrow&space;Na_{2}O$

Ans:- $4Na+O_{2}\rightarrow&space;2Na_{2}O$

b) $NaOH&space;+H_{2}SO_{4}\rightarrow&space;Na_{2}SO_{4}+H_{2}O$

Ans:- $2NaOH&space;+H_{2}SO_{4}\rightarrow&space;Na_{2}SO_{4}+2H_{2}O$

C)$H_{2}S+SO_{2}\rightarrow&space;S+H_{2}O$

Ans:- $2H_{2}S+SO_{2}\rightarrow&space;3S+2H_{2}O$

D) $Mg(OH)_{2}+HCl\rightarrow&space;MgCl_{2}+H_{2}O$

Ans:- $Mg(OH)_{2}+2HCl\rightarrow&space;MgCl_{2}+2H_{2}O$

E) $Al(OH)_{3}\rightarrow&space;Al_{2}O_{3}+H_{2}O$

Ans:- $2Al(OH)_{3}\rightarrow&space;Al_{2}O_{3}+3H_{2}O$

F) $BaCl_{2}+Na_{2}SO_{4}\rightarrow&space;BaSO_{4}+&space;NaCl$

Ans:- $BaCl_{2}+Na_{2}SO_{4}\rightarrow&space;BaSO_{4}+&space;2NaCl$

G)$Zn&space;+&space;HCl&space;\rightarrow&space;ZnCl_{2}+H_{2}$

Ans:- $Zn&space;+&space;2HCl&space;\rightarrow&space;ZnCl_{2}+H_{2}$

H) $Al(OH)_3\;+\;H_{2}SO_{4}\;\rightarrow\;Al_{2}(SO_{4})_{3}\;+\;H_{2}O$

Ans:- $2Al(OH)_3\;+\;3H_{2}SO_{4}\;\rightarrow\;Al_{2}(SO_{4})_{3}\;+\;6H_{2}O$

I) $CS_{2}\;+\;O_{2}\;\rightarrow\;CO_{2}\;+\;SO_{2}$

Ans:- $CS_{2}\;+\;3O_{2}\;\rightarrow\;CO_{2}\;+\;2SO_{2}$

In the reaction represented by the following equation:-

$CuO(s)\;+\;H_{2}(g)\;\rightarrow\;Cu(s)\;+\;H_{2}O(I)$

(a) Name the substance oxidized.

Ans:- H2.

(b) Name the substance reduced.

Ans:- CuO.

(c) Name the oxidizing agent.

Ans:- CuO.

(d) Name the reducing agent.

Ans:- H2.

Identify the components oxidized in the following chemical equations:-

(a) $2Cu\;+\;O_{2}\;\rightarrow\;2CuO$

Ans:- Cu.

(b) $2H_{2}\;+\;O_{2}\;\rightarrow\;2H_{2}O$

Ans:- H2.

(c) $2H_{2}S\;+\;SO_{2}\;\rightarrow\;3S\;+\;2H_{2}O$

Ans:- H2S.

(d) $ZnO\;+\;C\;\rightarrow\;Zn\;+\;CO$

Ans:- C.

Name the oxidizing and reducing agents in the following chemical reactions:-

(a) $H_{2}S\;+\;I_{2}\;\rightarrow&space;\;&space;2HI\;+\;S$

Ans:- H2S is a reducing agent and I2 is an oxidizing agent.

(b) $Zn\;+\;CuSO_{4}\;\rightarrow\;ZnSO_{4}\;+\;Cu$

Ans:- Zn is a reducing agent and CuSO4 is an oxidizing agent.

Identify the substance oxidized and reduced in the following chemical equations:-

(a) $MnO_{2}\;+\;4HCl\;\rightarrow\;MnCl_{2}\;+\;Cl_{2}\;+\;2H_{2}O$

Ans:- Here,

substance oxidized = HCl

And substance reduced = MnO2.

(b) $Fe_{2}O_{3}\;+\;3CO\;\rightarrow\;2Fe\;+\;3CO_{2}$

Ans:- Here,

substance oxidized = CO

And substance reduced = Fe2O3.

6.What happen when a piece of-
(a) Zinc metal is added to copper sulphate solution?
(b) Aluminium metal is added to dilute hydrochloric acid?
(c) Silver metals added to copper sulphate solution? Also, write the balanced equation if the reaction occurs?
Ans:- (a) when a Zn metal is added to copper sulphate solution then Zinc sulphate solution and copper are obtained.    $CuSO_{4}+\;Zn\rightarrow&space;ZnSO_{4}+Cu$
Ans:-(b) We know silver is less reactive than copper metal, So number displacement reaction will occur between silver and copper metal.
Ans:-(c) Aluminium metal reacts rapidly with dilute HCl to form aluminium chloride and hydrogen gas.   $2Al&space;+6HCL\rightarrow&space;2AICL_{3}+3H_{2}.$

7 On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and brown gas x is formed——–
(a) Write the balanced chemical equation of the reaction
(b) Identify the brown gas x evolved.
(c) Identify the type of reaction.
(d) What could be the $P^{H}$ range of aqueous solution of the gas x?
Ans:- (a)$2Cu(NO_{3})_{2}\overset{\Delta&space;}{\rightarrow}2CuO&space;+4NO_{2}&space;+O_{2}$
(b) The brown gas X is nitrogen dioxide ($NO_{2}$)
(c) Thermal decomposition.
(d)$P^{H}$<7, since $NO_{2}$ dissolves in water to form an acidic solution.

2. You are provided with two containers made up of copper and aluminium. You are pro-
vided with solutions of dilute HCI, dilute $HNO_{3}$, $ZnCl_{2}$, and $HNO_{3}$. In which of the above containers these solutions can be kept.
Ans:- Cu is less reactive metal and is placed below the hydrogen in activity series. So it does not react with HCl , $HNO_{3}$ , $ZnCl_{2}$and $H_{2}O$, On the otherhand Al is highly reactive metal and can reacts with the provided solutions.

5. Give the characteristic tests for the following gases —-
(a) $CO_{2}$(b) $SO_{2}$(c)$O_{2}$(d)$H_{2}$
Ans:-(a) when $CO_{2}$ gas is passed to lime water ,$[Ca(OH)_{2}]$ it turns milky white

(b) It turns acidified potassium dichromate solution from orange to green colour.
(c)$O_{2}$ gas is a good supporter of combustion.So when a burning matchstick is brought near the gas it burns more vigorously.

(d) If a burning matchstick is brought near Hydrogen, the matchsticks burns with ‘pop’ sound.