Question

What volume of a 1.7 M $HCl$ solution should be added to 200 mL of a 2.4 M $HCl$ solution which is finally diluted to 500 mL, so that molarity of the final $HCl$ solution becomes 1.3 M?

• A. 100 mL
• B. 140 mL
• C. 90 mL
• D. 240 mL

Answer 1

The correct option is A 100 mL

Let the volume of 1.7 M solution be $V_1$ mL.
Conserving the total moles before and after mixing:
$M_1{V}_1+M_2{V}_2=MV$
Where $M_2$ and $V_2$ are the molarity and volume of 2.4 M solution.
$(1.7\times V_1)+(2.4\times 200)=(1.3\times 500)$
On solving, $V_1=100$ mL
Hence, the volume of 1.7 M $HCl$ solution is 100 mL.