1. Concentration of Solutions

2. • The concentration of a solution is “the
amount of solute per quantity of solvent”
• There are many different ways of
expressing concentration:
▫ mass/volume percent (m/v %)
▫ mass/mass percent (m/m %)
▫ volume/volume percent (v/v %)
▫ parts per million (ppm)
▫ parts per billion (ppb)
▫ molar concentration (mol/L)

3. m/v %
• To calculate m/v % we use the following
equation:
• Mass of solute is in g
• Volume of solution is in mL

4. Example
• What mass of CuCl2(s) is required to make 1.0L
of 5.2% (m/v) CuCl2(aq)?

5. m/m %
• To calculate m/m% we use the following
equation:
• Mass of solute and mass of solution are in g

6. Example
• Brass has a (m/m) % composition of 85% Cu
and 15% Zn. If a sample of brass contains 5.21g
Cu, then what mass of Zn is present in the
sample?

7. v/v %
• To calculate v/v% we use the following equation:
• Volume of solute and volume of solution are
both in mL

8. Example
• Beer usually contains 5.0% (v/v) ethanol. How
much pure ethanol is present in one 341mL
bottle of beer?

9. Parts Per Million (ppm)
• As usual, both masses are in g
• Note that ppm does NOT refer to the number of
particles, but the masses of the solute and
solution

10. Parts Per Billion (ppb)
• Once again, both masses are in g
• Again, we are comparing masses, not number of
particles

11. Example
• A 155.3g sample of pond water is found to
contain 1.7x10-4g of phosphates. What is the
concentration of phosphates in ppm? In ppb?

12. Learning Check
• A 500.0 g bottle of water has a sodium ion
concentration of 5.50ppm. What mass of sodium
is present in the bottle?

13. Molar Concentration
• The molar concentration of a solution is the
number of moles of solute that are dissolved in
1L of solution
• Amount of solute is in mol
• Volume of solution is in L
• Molar Concentration is in mol/L

14. Example
• A 450.0 mL solution contains 0.75 mol of
CuCl2(s). What is the molar concentration of this
solution?

15. Learning Check
• 12.0g of sucrose (C12H22O11(s)) are dissolved in a
0.250 L aqueous solution. What is the molar
concentration of this solution?

16. Learning Check
• How many moles of HCl(s) are present in
587mL of a 2.5 mol/L solution?

17. Diluting Solutions
• Diluting means to take a stock solution (a highly
concentrated original solution) and add more
solvent to it

18. • We using the following formula to calculate how
to dilute a stock solution
• Ci = initial concentration
• Vi = initial volume
• Cf = final concentration
• Vf = final volume

19. Example
• Calculate the volume of water necessary to dilute
50 mL of a 0.50 mol/L sodium chloride solution
to 0.30 mol/L.

20. Homework
• Pg 373 Q 1-4
• Pg 375 Q 11, 14, 16
• Pg 376 Q 21, 23, 28
• Pg 378 Q 31, 34
• Pg 386 Q51, 53