(a) What is the difference between precipitation and neutralization reactions? What type of salts are prepared by neutralization and precipitation?
(b) Give examples in which physical and chemical changes occur simultaneously.
(c) What is photochemical reaction? Give one example.

Asked by Topperlearning User | 3rd Jun, 2016, 03:23: PM

Expert Answer:

(a)    Neutralisation reactions is a chemical double decomposition reaction in which H+ ions of an acid reacts with OH- ions of a base to form salt and water. In this reaction the the products formed are soluble. Whereas during precipitation, The solid particles, (precipitate) is formed. This precipitate is insoluble in water.

Soluble salts are prepared by neutralisation. Insoluble salts are prepared by precipitation.

(b)   (i) Heating of sodium nitrate

2NaNO3(s)  2NaNO3(l)            (Physical change)

2NaNO3(s)  2NaNO2   +   O2  (Chemical change)

 

(ii) Heating of zinc carbonate

  ZnO   ZnO                  (Physical change)

 White                Yellow

ZnCO3    ZnO  +  CO2   (Chemical change)

 

(C) Reactions which take place by the action of light are called as photochemical reactions or photolysis. Molecules of the reactants absorb light energy get activated and then react rapidly.

Example: Photosynthesis-Plants form glucose from carbon dioxide and water in presence of light.

6CO2  +  6H2O      C6H12O6  +  6O2

                                           (Glucose)

Answered by  | 3rd Jun, 2016, 05:23: PM

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