Solution
Concentration
Notes
CP Chemistry
Chapter 14
Concentration
• definition: the measure of how much solute is
dissolved in a specific amount of solvent
• can be dilute to concentrated
• can use specific numerical quantities to measure
concentration
o
o
o
o
% by mass
% by volume
dilutions
molarity
Percent by Mass &
Percent by Volume
solute
percent concentration 
 100
solution
solute
percent concentration 
 100
( solute  solvent )
Percent by Volume
Practice I
1. What is the percent by volume of ethanol in a
solution that contains 35 mL of ethanol dissolved in 115
mL of water?
solute
percent concentration 
 100
( solute  solvent )
Percent by Volume
Practice I cont’d
2. If you have 100 mL of a 30% aqueous solution of
ethanol, what volume of ethanol and water are in the
solution?
Percent by Volume
Practice I cont’d
3. What is the percent by volume of isopropyl alcohol
in a solution that contains 24 mL isopropyl alcohol in
1100 mL of water?
Percent by Volume
Practice I cont’d
4. What is the percent by volume of 140 mL of
isopropyl alcohol dissolved in 60 mL of water?
Percent by Volume
Practice I cont’d
5. A bottle of hydrogen peroxide is labeled 3%. If you
pour out 50 mL, what volume of hydrogen peroxide
have you poured out?
Percent by Volume
Practice I cont’d
6. If 50 mL of pure acetone is mixed with 450 mL of
water, what is the percent by volume?
Percent by Volume
Practice I cont’d
7. If you have 500 mL of a 10% solution of tetracycline,
what is the volume of tetracycline and water?
Percent by Volume
Practice I cont’d
8. If you pour out 60 mL of a 30% alcohol solution, how
much pure alcohol have you poured?
Percent by Mass Practice I
1. What is the % concentration by mass of 8.3 g of NaCl dissolved in 300 g of water?
(2.7%)
2.
What is the % concentration by mass of 65 g of C6H12O6 dissolved in 500 g of
water? (11.5%)
3. You have a 1000 g bleach solution. The % concentration by mass of the solute
NaOCl is 6.02 % . How many grams of the NaOCl are in the solution? (60.2 g)
4. How many grams of water would you have to add to 50 g of NaCl to produce a
solution concentration of 5%? (950 g)
5. What is the solution concentration by mass of 12 grams of NaCl dissolved in 300
grams of water? (3.8%)
6. If you need to produce 500 grams of an 8.3% saline solution, how many grams of
salt and how many grams of water would you use to form the solution? (41.5 g of
salt, 458.5 g H2O)
Diluting Solutions
• Concentrated stock solutions of chemicals are
purchased in the laboratory because they are
much more economical to buy
• These solutions are diluted to desired
concentrations that are required by the labs we
perform in class
• To properly dilute solutions we use the following
equation:
o Where ‘M’ = Molarity
o Where ‘V’ = Volume
Diluting Solutions
Examples
1. What volume of a 3M KI solution would you use to make
.3 L of a 1.25M KI solution?
2. How many milliliters of a 5M H2SO4 solution would you
need to prepare 100 mL of .25 M H2SO4?
3. If you dilute 20 mL of a 3.5M solution to make 100 mL of
solution, what is the molarity of the dilute solution?
125 mL, 5 mL, .7M
Molarity
• concentration expressed as the number of moles of
solute per liter of solution
• use M, molar
o ex. 2.5 M solution is a 2.5 molar solution
• Conversion reminder: to convert mL to L, must
divide by 1000 (1000 mL = 1 L)
Molarity Equations
• 𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦 =
• 𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦 =
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒
𝐿𝑖𝑡𝑒𝑟𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛
# 𝑜𝑓 𝑔𝑟𝑎𝑚𝑠 𝑠𝑜𝑙𝑢𝑡𝑒
𝑀𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑠𝑜𝑙𝑢𝑡𝑒
𝐿𝑖𝑡𝑒𝑟𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛
Molarity Example
Problem #1
What is the molarity of a solution containing 158
grams of sodium chloride, NaCl, in 2.5 liters of water?
Molarity Example
Problem #2
Calculate the molarity of 250 mL solution containing
75 grams of H2SO4.
Molarity Example
Problem #3
How many grams of NaCl would be dissolved in 1.75 L
of a 0.85 M solution of NaCl?