Question

Alkalinity of water cannot be due to the simultaneous presence of OH-

,

CO32-

and HCO3-

ions. Why?

​

Answer 1

Water Alkalinity is mainly due to carbonate and bicarbonate salts in a water sample, the carbonate ion has two end points, one from carbonate to bicarbonate and another from bicarbonate to carbon dioxide.

phenolphalein end point pink to clear

 

methyl orange end point yellow to red.

Answer 2

The alkalinity of water cannot be due to the simultaneous presence of OH-, CO32-, and HCO3-ions because it is not only carbonate which occursthat causes the alkalinity.

Explanation:

The alkalinity of water is due to the presence of carbonate, bicarbonate & hydroxide ion which is present in water.

It is the mixture of two ions present in water.

The presence of $OH- and HCO3-$  ions together is not possible since they combine together to form $CO3-2$ ions.

Thus $OH-$and $HCO3-$ ions cannot exist together in water and hence can be concluded that all the three $OH- , HCO3- ,CO3-2$ions cannot exist together .