Q13 of 15 Page 35

Identify the type of chemical reaction taking place in each of the following:

(a) Barium chloride solution is mixed with copper sulphate solution and a white precipitate is observed.


(b) On heating copper powder in air in a china dish, the surface of copper powder turns black.


(c) On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of a gas having odour of burning sulphate is experienced.


(d) Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the blue colour of copper sulphate fades away.


(e) Quick lime reacts vigorously with water releasing a large amount of heat.

(a) Double displacement and precipitation reaction

When barium chloride solution is mixed with copper sulphate solution and a white precipitate is observed.


In double displacement reaction, a precipitate is formed which settles down at the bottom. Any reaction that produces a precipitate is called a precipitation reaction.


BaCl2 + CuSO4→ BaSO4 (↓) + NaCl White ppt.


Note: A precipitate is a substance which is insoluble in water.


(b) Oxidation reaction


On heating copper powder in air in a china dish, the surface of copper powder turns black because copper undergoes oxidation in the presence of air.


2Cu +O2→ 2CuO Black


(c) Thermal decomposition


On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of a gas having odour of burning sulphate is experienced.



In the above reaction, ferrous sulphate (FeSO4) decomposes to ferric oxide (Fe2O3)


(d) Displacement reaction


Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the blue colour of copper sulphate fades away.


Fe + CuSO4→ FeSO4 + Cu


As we know that displacement reaction is a reaction in which one element displaces other element from its compound and takes its place there in.


In the above reaction Fe replaces Cu and form a new compound.


(e) Exothermic reaction


Quick lime reacts vigorously with water releasing a large amount of heat:


CaO + H2O → Ca(OH)2 + heat


In the above reaction, the heat is released. Hence, it is an exothermic reaction.


Exothermic reaction is a reaction in which heat is released when reactants changes into products.


More from this chapter

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10

Identify the oxidising agent (oxidant) in the following reactions:

(a) Pb3O4 + 8HCl → 3PbCl2 + Cl2 + 4H2O


(b) 2Mg + O2→ 2MgO


(c) CuSO4 + Zn → Cu + ZnSO4


(d) V2O5 + 5Ca → 2V + 5CaO


(e) 3Fe + 4H2O → Fe3O4 + 4H2


(f) CuO + H2→ Cu + H2O

 11

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

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


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


(c) Ethanol is warmed with ethanoic acid to form ethyl acetate in presence of conc. H2SO4.


(d) Ethene is burnt in presence of oxygen to form carbon dioxide, water and releases heat and light.

 12

Complete the missing components/variables given as x and y in the following reactions:

(a) Pb(NO3)2(aq) + 2Kl(aq) → PbI2(x) + 2KNO3(y)


(b) Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + x


(c) Zn(s) + H2SO4(aq) → ZnSO4(x) + H2(y)


(d) CaCO3(s) CaO(s) + CO2 (g)

14

Seema likes sugar apple which is a multipurpose, an all-rounder fruit. It can be used by athletes as high calorie fruit for high energy. The powdered of its seeds is an effective pesticide in agriculture and horticulture and also used to remove head lice. Its leaves have anti-diabetic properties. The alcoholic extract of its leaves and stems can treat tumours. This extract is an antidepressant. Fruits are sweet and increase the haemoglobin, cooling and act as sedative. Seeds are insecticides. Its roots are powerful purgatives and used in dysentery.

(a) Why is sugar apple used by athletes?


(b) Why should we use it as a pesticides and insecticides instead of chemicals? Which value is associated with its use?


(c) Which metal is present in haemoglobin?


Name one more fruit which is rich in iron?


(d) Why should people take fruits rich in iron?


(e) What values are possessed by Seema who uses this multipurpose fruit instead of junk food?