Question

10mL volume of 75mM EtOH is necessary for an experiment. What volumes of 1M EtOH and water should be mixed to obtain the working concentration?

Answer 1

Answer: Volume of the 1M EtOH and water should be 0.75 ml and 9.25 ml respectively to obtain the working concentration.

Explanation:

According to the dilution law,

$C_1V_1=C_2V_2$

where,

$C_1$ = molarity of stock solution = 1M

$V_1$ = volume of stock solution = ?

$C_2$ = molarity of diluted solution = 0.075 M    (1mM=0.001M)

$V_2$ = volume of diluted solution = 10 ml

Putting in the values we get:

$1M\times V_1=0.075M\times 10ml$

$V_1=0.75ml$

Thus 0.75 ml of 1M EtOH is taken and (10-0.75)ml = 9.25 ml of water is added to make the volume 10ml.

Therefore, volume of the 1M EtOH and water should be 0.75 ml and 9.25 ml respectively to obtain the working concentration