Q15 of 30 Page 1

Mention with reason the colour change observed when:

(i) silver chloride is exposed to sunlight.


(ii) copper powder is strongly heated in the presence of oxygen


(iii) a piece of zinc is dropped in copper sulphate solution.


(i) When silver chloride is exposed to sunlight. It undergoes photochemical decomposition forming grey metal silver and greenishyellow gas chlorine is involved



(ii) When copper powder is strongly heated in the presence of oxygen then copper react withoxygen present in air to form copper oxide by combination reaction.Copper oxide which is black in colour.



(iii) When a piece of zinc is dropped in Cuso4 solution then zinc being more reactive displaces copper from copper sulphate and form S zinc sulphate solution.



More from this chapter

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13

Assertion (A): Following are the members of a homologous series:

CH3OH, CH3CH2OH, CH3CH2CH2OH


Reason (R): A series of compounds with same functional group but differing by -CH2- unit is called a homologous series.


 14

Assertion (A): Alloys are commonly used in electrical heating devices like electric iron and heater.

Reason (R): Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points then their constituent metals.


 16

Complete and balance the following chemical equations:

(i) NaOH(aq) + Zn(s)→


(ii) CaCO3(s) + H2O(l) + CO2(g)→


(iii) HCl(aq) + H2O(l)→


OR


During electrolysis of brine, a gas ‘G’ is liberated at anode. When this gas ‘G’ is passed through slaked lime, a compound ‘C’ is formed, which is used for disinfecting drinking water.


(i) Write formula of ‘G’ and ‘C’.


(ii) State the chemical equation involved.


(iii) What is common name of compound ‘C’? Give its chemical name.


 17

Study the data of the following three categories A, B
and C.




(i) From the given three categories A, B and C, pick the one which forms Dobereiner Triads.


(ii) Why did Mendeleev laced elements of category A, B and C in three different groups?


(iii) Is Newland law of octaves applicable to all the three categories? Give reason to justify your answer.