Question

1. You are asked to make 200 mls of a 20mM working (diluted) solution of NaCl using a 2M stock solution. Record the volume of 2M stock solution and the volume of water you would use the make the working (diluted) solution.

Answer 1

Answer:

The volume of 2M stock solution added = 2 mL

The volume of water = 198 mL

Explanation:

Considering

$Molarity_{working\ solution}\times Volume_{working\ solution}=Molarity_{stock\ solution}\times Volume_{stock\ solution}$

Given  that:

$Molarity_{working\ solution}=20\ mM=0.02\ M$

$Volume_{working\ solution}=200\ mL$

$Volume_{stock\ solution}=?$

$Molarity_{stock\ solution}=2\ M$

So,  

$0.02\ M\times 200\ mL=2\ M\times Volume_{stock\ solution}$

$Volume_{stock\ solution}=\frac{0.02\times 200}{2}\ mL=2\ mL$

The volume of 2M stock solution added = 2 mL

The volume of water = 200 - 2 mL = 198 mL