1. How to mix a Standard Solution
Use a VOLUMETRIC FLASK to make a standard solution of known concentration
Step 1> add the weighed amount of solute in the volumetric flask
Step 2> add distilled water (about half of final volume)
Step 3> cap volumetric flask, and shake to dissolve solute completely
Step 4> add distilled water to volume marker (calibration mark)
The solution process may be exothermic (release heat). This may cause the liquid to show a larger volume than is real. Allow the solution to return to ambient (room) temperature and check volume again.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 480

2. Process of Making a Standard Solution from Liquids
Solutions can be made using liquids or solids (or gases).
To make a 5% solution v/v (volume to volume)
This means to add 5 mL of solute in 95 mL of solvent. The total is 5 mL / 100 mL or 5%.
For the diagram add 25 mL of liquid solute and add water to bring volume to 500 mL (about 475 mL water).
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 483

3. Markings on Glassware Beaker 500 mL + 5% Range = 500 mL + 25 mL
Graduated Cylinder
Volumetric Flask
500 mL mL
Range = – mL
TC 20oC “to contain at a temperature of 20 oC” 22
TD “to deliver” T s
“time in seconds”

4. Concentration…a measure of solute-to-solvent ratio
concentrated dilute
“lots of solute” “not much solute”
“watery”
Add water to dilute a solution; boil water off to concentrate it.

5. A. mass % = mass of solute
mass of sol’n
B. parts per million (ppm)  also, ppb and ppt
-- commonly used for minerals or
contaminants in water supplies
C. molarity (M) = moles of solute
L of sol’n
-- used most often in this class
mol L M
D. molality (m) = moles of solute
kg of solvent

6. WRONG
7.85 kg KCl are dissolved in 2.38 L of solution.
Find molality.
24.8 g table sugar (i.e., sucrose, C12H22O11) are mixed into 450 g water.
Find molality.

7. What mass of CaF2 must be added to 1,000 L of water
so that fluoride atoms are present at a conc. of 1.5 ppm?
= 3.34 x 1028 m’cules H2O

8. mol L M
How many moles solute are required to make 1.35 L of 2.50 M solution?
mol = M L = 2.50 M (1.35 L) =
3.38 mol
A. What mass sodium hydroxide is this?
B. What mass magnesium phosphate is this?

9. Find molarity if 58.6 g barium hydroxide are in 5.65 L solution.

10. You have 10.8 g potassium nitrate.
How many mL of solution will make this a 0.14 M solution?
convert to mL

11. 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

12. SAWS Water Quality Report - June 2000
Concentration
SAWS Water Quality Report - June 2000

13. Molality
mass of solvent only
1 kg water = 1 L water

14. Molality
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

15. Molality
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

16. Molarity of Solutions Molarity of Solutions Molarity of Solutions