An oxy acid of phosphorus has the following properties.
Complete neutralization of the acid with sodium hydroxide solution gives an aqueous solution of sodium ions and oxy acid anions in the ratio 2 : 1. When a solution of acid is warmed with silver nitrate solution metallic silver is deposited.
pH of 0.01 M solution of the sodium salt of this acid formed (assume `pK_(a) = 2x`) is
A. `6 + 2x`
B. `6 - 2x`
C. `6 - x`
D. `6 + x`.
