Question

You have a 1.212 M stock aqueous solution of Sr(OH)2. What volume of thestock solution (in mL) must be diluted with water to prepare 50.00 mL of a solutionthat has a hydroxide concentration [OH–] = 0.2000 M?

Answer 1

Answer: The volume of stock solution of strontium hydroxide needed is 4.125 mL

Explanation:

1 mole of $Sr(OH)_2$ produces 1 mole of strontium ions and 2 moles of hydroxide ions

Molarity of diluted strontium hydroxide solution = $\frac{0.200}{2}=0.100M$

To calculate the molarity of the diluted solution, we use the equation:

$M_1V_1=M_2V_2$

where,

$M_1\text{ and }V_1$ are the molarity and volume of the concentrated strontium hydroxide solution

$M_2\text{ and }V_2$ are the molarity and volume of diluted strontium hydroxide solution

We are given:

$M_1=1.212M\\V_1=?mL\\M_2=0.100M\\V_2=50mL$

Putting values in above equation, we get:

$1.212\times V_1=0.100\times 50\\\\V_1=\frac{0.1\times 50}{1.212}=4.125mL$

Hence, the volume of stock solution of strontium hydroxide needed is 4.125 mL