How much water should be added to `2M HCl` solution to form `1"litre"` of `0.5M HCl` ? .

Explanation

Let `V` be initial volume
Then mol of `HCl` = constant
`2 xx V = 1 xx 0.5 " "rArr" " V =0.25 L`
Volume of water added `=1 - 0.25 = 0.75 L` .