Question

what volume of 1.90 m srcl₂ is needed to prepare 525 ml of 5.00 mm srcl₂?

Explanation:

Step1: Convert mM to M

$5.00\ mM = 5.00\times10^{- 3}\ M$

Step2: Use dilution formula $M_1V_1 = M_2V_2$

Let $M_1 = 1.90\ M$, $V_1$ be the volume of concentrated solution we need to find, $M_2=5.00\times 10^{-3}\ M$ and $V_2 = 525\ mL$.
$V_1=\frac{M_2V_2}{M_1}$

Step3: Substitute values

$V_1=\frac{5.00\times 10^{-3}\ M\times525\ mL}{1.90\ M}$
$V_1=\frac{5.00\times525\times 10^{-3}}{1.90}\ mL$
$V_1=\frac{2.625}{1.90}\ mL\approx1.38\ mL$

Answer:

$1.38$