Question

How much water should be added to 750 mL of a 2.8 M HCl solution to make a 1.0 M resultant solution?

• A. 0.75 L
• B. 1.25 L
• C. 1.35 L
• D. 1.00 L

Answer 1

The correct option is C 1.35 L

$M_1{V}_1=M_2{V}_2$
$M_1$ and $M_2$ are the concentrations of the given solution and the resultant solution respectively and $V_1$ and $V_2$ are their respective volumes.
$M_1=2.8M,V_1=750mL;M_2=1.0M$
$\left(2.8M\right)\times \left(750mL\right)=\left(1.0M\right)\times V_2$
$V_2=\frac{\left(2.8M\right)\times \left(750mL\right)}{\left(1.0M\right)}$ = 2100 mL = 2.1 L
Volume of water to be added $=2.1L-0.75L=1.35L$