# Question #25bc8

$0.25 M$ means there is already an aqueous solution of $N a C l$; therefore you need to add $8.0 L$ of water to make the desired molarity/volume of solution.
$0.25 M \cdot {V}_{1} = 0.2 M \cdot 10 L$
$\therefore {V}_{1} = 8.0 L$