Question

Consider the following information about the diprotic acid, ascorbic acid. (H₂As for short, molar mass 176.1)

H₂As HAs

Answer 1

Na₂ As (Sodium Ascorbate ) being a salt solution reacts with standard HCl solution being gradually added to it yielding a diprotic acid H₂ As. The reaction therefore would take place in two diferent well categorized steps-

( ! ) Formation of NaAsH representing half reaction

( 2 ) Na As H would again react till complete neutralization /reaction.

Note that HCl solution has been used to estimate the alkaline / basic nature of the reaction medium caused by the hydrolysis of the salt.

With these considerations the answers are-

1. E ( ie. H₂As , H+ ) - since the solution would remain acidic at thisstage ,

2. A ( pH would remain acidic even after adding !/2 HCl ie. 4.2 ) at point I

3. B ( because at this stage at point III the end point is closer to neutral nature of the reaction medium.It should not be acidic or highly alkaline as noted with other options provided for pH values )

4 C As^2- (The major species present when the reaction is almost complete at point IV )