This document provides instructions and definitions for preparing chemical solutions and reagents. It discusses the types of vessels used to hold solutions, defines key terms like solutes, solvents, concentration, and amount. It also covers how to make solutions of different concentrations by mass, volume, percentage, molarity and describes how to dilute stock solutions to achieve desired concentrations. The goals are to teach how to properly make and measure solutions for experiments.

1. PREPARING SOLUTIONS AND
REAGENTS

2. Chemical Solutions
(aqueous = water is the solvent)
Types of vessels (least to most precise):
 Beaker
 Erlennmeyer flask
 Graduated cylinder
 Volumetric flask

3. DEFINITIONS:
• SOLUTES -- substances that are
dissolved
• SOLVENTS -- substance in which
solutes are dissolved (usually water)
• AMOUNT -- how much

4. Goals
• Make solutions
• Dilute solutions
• Convert between different concentrations
of solutions

5. Facts of Life
• Mass is measured in Grams, mg, μg
1g = 1000mg = 1,000,000µg
• Volume is measured in liters, mL, μL
1L = 1000mL = 1,000,000 μL
• Density of water is 1 g / mL

6. Facts of life (cont’d)
• Concentration means: amount of solute in
a volume of solution
• Expressed in many ways:
– 1. percent
– 2. mg/ mL
– 3. molar
– 4. “X” solution

7. Each star represents 1 mg of NaCl.
What is the total amount of NaCl in the tube? _____
What is the concentration of NaCl in the tube (in
mg/mL)? _____
8 mL
5 mg = ?
8 mL 1 mL
? = 0.63 mg, so the
concentration is
0.63 mg/mL

8. Percent Solutions
• Per means “for every one”
• Cent means 100
• Example: a 5% sugar solution has
5 grams of sugar for 100g of solution, or
5g 100 g of water = 100 mL, and the
100mL solution is mostly water.

9. Make 250 mL of a 3% starch
solution
3 g / 100 g = 3 g / 100 mL because density of
water is 1 g / mL
Set up a ratio:
3 g / 100 mL = ?g / 250 mL
Use 7.5 g of starch and bring to a volume of (BTV)
250 mL with distilled water

10. • 5 mg/mL has 5 milligrams of solute in 1
milliliter of solution
mg / mL Solutions

11. Set up a ratio:
3 mg / 1 mL = ?mg / 250 mL
Use 750 mg of starch and bring to a volume
of (BTV) 250 mL with distilled water
Make a 250 mL of a 3 mg /mL
starch solution

12. Molar Solutions
• 1 mole is 6.02 x 1023 items
• Molecular weight or Formula weight is
really the mass of 1 mole of molecules
(see periodic table)
Example: 1 mol of sodium chloride (NaCl)
has a mass of 58.44 g.

13. MOLARITY
• Molarity is: number of moles of a solute
that are dissolved per liter of total solution.
• A 1 M solution contains 1 mole of
solute per liter total volume.

14. MOLE
• How much is a mole?

15. EXAMPLE: SULFURIC ACID
For a particular compound, add the atomic weights
of the atoms that compose the compound.
H2SO4:
2 hydrogen atoms 2 X 1.00 g = 2.00 g
1 sulfur atom 1 X 32.06 g = 32.06 g
4 oxygen atoms 4 X 16.00 g = 64.00 g
98.06 g

16. EXAMPLE CONTINUED
• A 1M solution of sulfuric acid contains
98.06 g of sulfuric acid in 1 liter of total
solution.
• "mole" is an expression of amount
• "molarity" is an expression of
concentration.

17. DEFINITIONS
• "Millimolar", mM, millimole/L.
– A millimole is 1/1000 of a mole.
• "Micromolar", µM, µmole/L.
– A µmole is 1/1,000,000 of a mole.

18. FORMULA
HOW MUCH SOLUTE IS NEEDED FOR A SOLUTION OF
A PARTICULAR MOLARITY AND VOLUME?
(g solute ) X (mole) X (L) = g solute needed
1 mole L
or
FW X molarity x volume = g solute needed

19. EXAMPLE
How much solute is required to make 300
mL of 0.8 M CaCl2?

20. ANSWER
(111.0 g) x (0.8 mole) x (0.3 L) = 26.64 g
mole L

21. • Make 250 mL of a 3 molar NaCl solution
58.44g x 3 moles x 0.25 L = ? g
1 mole 1 L
? = 43.8g of NaCl
BTV of 250 mL

22. “X” solutions
• X means times
• A 40X buffer solution is 40 times more
concentrated than the standard working
solution
• Stock solutions / concentrates
• How much stock solution you need =
total volume you need divided by
the “X” number

23. Diluting Solutions
• Conc 1 x Vol. 1 = Conc 2 x Vol 2
• Usually want 1 X solutions

24. Example: Frozen Orange Juice
• Solution 1 is the frozen concentrate
• Solution 2 is the 1X juice you drink
• How concentrated is it?
• C1 V1 = C2 V2
• (? X) (250mL) = (1X) (1000 mL)

25. Answer:
Frozen OJ is 4X because ¼ of the
final volume is the concentrated oj

26. Example: bleach sterilant
• Solution 1 is 100% bleach – stock solution
• Solution 2 is 6% bleach – what you want
• How do you make 350 mL of 6% bleach?
• C1 V1 = C2 V2
• (100%) (?) = (6%) (350 mL)

27. Answer:
You need 21 mL of 100% bleach
BTV 350 mL.