250 ml of 6 M HCl and 650 ml of 3 M HCl were mixed together. What volume of water is to be added so that the molarity of the final solution is 3 M ?

Options

A. 300 ml
B. 1150 ml
C. 250 ml
D. 135 ml

Answer

C

Explanation

Moles of HCl in 250 ml of 6M `=(6xx250)/(1000)`
`=1.5` moles
Moles of HCl in 650 ml of `3M=(3xx650)/(1000)`
`=1.95` moles
Total moles `=1.5+1.95=3.45` moles
Molarity of solution `=(3.45)/(900)xx1000`
`=3.833M`
`M_(1)V_(1)=M_(2)V_(2)`
`3.833xx900=3.0xxV_(2)`
or `V_(2)=(3.833xx900)/(3.0)=1150` ml
Volume of water added `=1150-900`
`=250` ml