Question

1)write a detailed procedure for the determination of various form:
Of alkalinity in a given water sample?​

Answer 1

Answer:

The alkalinity of water can be determined by titrating the water sample with

Sulphuric acid of known values of pH, volume and concentrations. Based on

stoichiometry of the reaction and number of moles of Sulphuric acid needed to

reach the end point, the concentration of alkalinity in water is calculated.

When a water sample that has a pH of greater than 4.5 is titrated with acid to a

pH 4.5 end point, all OH-

, CO3

2-

, and HCO3

- will be neutralized.

For the pH more than 8.3, add phenolphthalein indicator, the colour changes to

pink colour. This pink colour is due to presence of hydroxyl ions.

If sulphuric acid is added to it, the pink colour disappears i.e. OH- ions are

neutralized.

Then add mixed indicator, the presence of CO3

2- and HCO3

- ions in the solution

changes the colour to blue. While adding sulphuric acid, the color changes to red,

this color change indicates that all the CO3

2- and HCO3

- ions has been

neutralized. This is the end point.