1. II. Solution Concentration (p. 480 – 486)
Ch. 16 – Solutions
II. Solution Concentration (p. 480 – 486)

2. A. Concentration The amount of solute in a solution
Describing Concentration
% by mass - medicated creams
% by volume - rubbing alcohol
ppm, ppb - water contaminants
molarity - used by chemists
molality - used by chemists

3. substance being dissolved
B. Percent Solutions
Percent By Volume (%(v/v))
Concentration of a solution when both solute and solvent are liquids often expressed as percent by volume
substance being dissolved
total combined volume

4. B. Percent Solutions
Find the percent by volume of ethanol (C2H6O) in a 250 mL solution containing 85 mL ethanol.
Solute = 85 mL ethanol
Solution = 250 mL
85 mL ethanol
250 mL solution
% (v/v) =
= 34% ethanol (v/v)
x 100

5. substance being dissolved
B. Percent Solutions
Percent By Mass (%(m/m))
Concentration of a solution when solute is solid sometimes expressed as percent by mass
substance being dissolved
total combined volume

6. B. Percent Solutions
How much glucose should you use to make g of a 2.8% (m/m) solution in water?
Percent (m/m) = 2.8%
Solution = g
unknown g glucose
2000. g solution
2.8 =
= g glucose
x 100

7. substance being dissolved
C. Molarity
Concentration of a solution most often used by chemists
substance being dissolved
total combined volume

8. C. Molarity
2M HCl
What does this mean?

9. D. Molarity Calculations
LITERS
OF GAS
AT STP
Molar Volume
(22.4 L/mol)
MASS IN
GRAMS
MOLES
NUMBER OF
PARTICLES
Molar Mass
(g/mol)
6.02  1023
particles/mol
Molarity
(mol/L)
LITERS OF
SOLUTION

10. D. Molarity Calculations
How many moles of NaCl are required to make 0.500L of 0.25M NaCl?
0.500 L sol’n
0.25 mol NaCl
1 L sol’n
= mol NaCl

11. D. Molarity Calculations
How many grams of NaCl are required to make 0.500L of 0.25M NaCl?
0.500 L sol’n
58.44 g NaCl
1 mol NaCl
0.25 mol NaCl
1 L sol’n
= 7.3 g NaCl

12. D. Molarity Calculations
Find the molarity of a 250 mL solution containing 10.0 g of NaF.
10.0 g NaF
1 mol NaF
41.99 g NaF
= 0.95 M NaF
.25 L sol’n

13. E. Dilution
Preparation of a desired solution by adding water to a concentrate
Moles of solute remain the same

14. E. Dilution
What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?
GIVEN:
M1 = 15.8M
V1 = ?
M2 = 6.0M
V2 = 250 mL
WORK:
M1 V1 = M2 V2
(15.8M) V1 = (6.0M)(250mL)
V1 = 95 mL of 15.8M HNO3

15. F. Molality
mass of solvent only
1 kg water = 1 L water

16. G. Molality Calculations
Find the molality of a solution containing 75 g of MgCl2 in 250 mL of water.
75 g MgCl2
1 mol MgCl2
95.21 g MgCl2
0.25 kg water
= 3.2m MgCl2

17. G. Molality Calculations
How many grams of NaCl are req’d to make a 1.54m solution using kg of water?
0.500 kg water
1.54 mol NaCl
1 kg water
58.44 g NaCl
1 mol NaCl
= 45.0 g NaCl

18. H. Preparing Solutions 1.54m NaCl in 0.500 kg of water
500 mL of 1.54M NaCl
mass 45.0 g of NaCl
add water until total volume is 500 mL
mass 45.0 g of NaCl
add kg of water
500 mL water
45.0 g NaCl
500 mL
mark
volumetric
flask

19. H. Preparing Solutions
Copyright © NT Curriculum Project, UW-Madison
(above: “Filling the volumetric flask”)

20. H. Preparing Solutions
Copyright © NT Curriculum Project, UW-Madison
(above: “Using your hand as a stopper”)

21. H. Preparing Solutions 250 mL of 6.0M HNO3 by dilution
measure 95 mL of 15.8M HNO3
95 mL of 15.8M HNO3
combine with water until total volume is 250 mL
250 mL mark
Safety: “Do as you oughtta, add the acid to the watta!” or AA – add acid!
water for safety

22. Solution Preparation Mini-Lab
Turn in one paper per team.
Complete the following steps:
A) Show the necessary calculations.
B) Write out directions for preparing the solution.
C) Prepare the solution.
For each of the following solutions:
1) mL of 0.50M NaCl
2) 0.25m NaCl in mL of water
3) mL of 3.0M HCl from 12.0M concentrate. (don’t actually prepare this one!)