The stages in the purification of water is given as follows:
(i) Sedimentation
(ii) Chlorination
(iii) Filtration
Which of the following correctly represents order of
purification of water?
A (ii) → (iii) → (i)
B (ii) → (i) → (iii)
C (iii) → (ii) → (i)
D (i) → (ii) → (iii)
ans. is wrong. it should be I, iii,ii
Ans 4:
Class : Class 5
The correct option should be - 1-3-2 ( Sedimentation - Filtration - Chlorination )This option is not given. Sedimentation - All the particles settle down as gravity pulls the heavier sediments down.Filtration - It removes the sediments from the water.Chlorination - Process of adding chlorine to water and removing the parasites,bacteria and viruses. Now the water is purified.
Ans 8:
Class : Class 4
the correct order is 1,3,2 but there is no option like that but if you look at option A you'll find the correct order in a descending order (from back) so if there is no option like 1,3,2 then A should be correct
Ans 12:
Class : Class 6
1-3-2 is the correct order as first we should remove all the insoluble impurities and the the soluble impurities.
Ans 14:
Ans 19:
Class : Class 5
The correct order is 1-3-2 and there is no option like that .So,I think that it might be a printing error.
Ans 23:
Class : Class 5
(i) Sedimentation - Sedimentation is a physical water purification process using gravity to remove suspended solid impurities from water. The water is allowed to stand till the suspended solid impurities, which are heavier than water, are pulled down by gravity and settle at the bottom of the container.(ii) Chlorination - Chlorination is the process of adding chlorine, or chlorine compounds such as sodium hypochlorite, to drinking water to disinfect it and kill germs. The addition of chlorine will also oxidize any iron, manganese and/or hydrogen sulphide that are present, so that they too can be removed in the filtration process later on.(iii) Filtration - Filtration is a process of water purification, which is used to separate solid impurities from water by using a filter medium that allows the water to pass through but not the solid impurities. These solid impurities are not heavy, so they do not settle at the bottom, but remain suspended. So, a filter is used to trap them.So, to purify water, it must go through sedimentation (i) first, so that heavier and larger size impurities like sand and dirt, are allowed to settle at the bottom of the container and are removed first. Next, water must go through chlorination (ii), so that bacteria and germs present in water are killed. Any iron, manganese and/or hydrogen sulphide, if present, also get oxidized by chlorine. These can be removed later by the filtration (iii) process, along with other suspended impurities.Hence, the right answer is Option D.