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Diluting a Solution. Most solutions are stored in concentrated form and diluted for use when required. To dilute to the required concentration we must extract the number of moles required from the stock solution and place them in the new flask. Fill it with water and we are done.
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Diluting a Solution • Most solutions are stored in concentrated form and diluted for use when required. • To dilute to the required concentration we must extract the number of moles required from the stock solution and place them in the new flask. • Fill it with water and we are done
The number of moles does not change when you dilute the solution, therefore: • Since n = Cv in both beakers, we can write the relationship as : • Civi = CfvfCi = Concentration of the initial solutionvi = volume of the initial solutionCf = Concentration of the final solutionvf = volume of the final solution
EXAMPLE 1 • What volume of 12.4 mol/L hydrochloric acid is required to prepare 2.00 L of 0.250 mol/L solution.- note: whenever you want to prepare something, this will be a final concentration or volume
ANSWER • Civi = Cfvf • 12.4 M (v) = 2.00 L x 0.250 M • v= (2.00L) x (0.250M/12.4M) • v = 0.0403 L or 40.3 mL
EXAMPLE 2 • What is the concentration of the diluted acetic acid if 200 mL of 17.4 M is pipette into a 500 mL flask and brought up to the full volume?
ANSWER #2 • Civi = Cfvf (note:200mL=0.200L) • 17.4 M x 0.200 L = Cf x 0.500 L • Cf = 6.96 M