Q. The amount of water to be added to 10 ml of 10 N HCL solution to make it decinormal solution is

A) 1000 ml
B) 990 ml
C) 100 ml
D) 10 ml

... Answer is B). 990 ml

      N1V1 = N2V2

So 10x10 = 0.1 x V. 

or V = 1000 ml

So extra water addes will be 990 ml