An aqueous solution of HCl has a pH of 2.0 When water is added to increase the pH to 5.0 the hydrogen ion concentration -

Options

A. Remains the same
B. Decreases three -fold
C. Increases three -fold
D. Decreases thousand -fold

Answer

D

Explanation

`pH = rArr [H^(+)] = 10^(-2)`
`pH = 5 rArr [H^(+)] = 10^(-5)`
`:. ([H^(+)]"new")/([H^(+)]"old") = (10^(-5))/(10^(-2))=10^(-3)`