Solutions and Concentration
What is concentration?The amount of substance within a given volume
𝐂 =𝑴
𝑽C: concentration (g/L)m: mass of solute (grams)V: volume of solution (litres)
Remember: 1 L = 1000 ml
What is percentage?
“per 100”
Percentage10
10
What percentage of the squares are grey?
Grey squares = 20
Total squares = 100
Percentage = 20%
• We can also measure concentration in % (m/V)
Percent (m/V)
What is the % concentration?
1 ml of water (solvent)
1 g of solute
C=?m= 2gV = 25ml
C= 𝑚
𝑉=
2𝑔
25𝑚𝑙
2𝑔
25𝑚𝑙=
𝑥𝑔
100𝑚𝑙
8%
Situation
Practice Problem1. What is the % concentration of sugar in a 355ml can of Coca-Cola?
C=?m= 42gV = 355ml
C= 𝑚
𝑉=
42𝑔
355𝑚𝑙
42𝑔
355𝑚𝑙=
𝑥𝑔
100𝑚𝑙
11.83%
Practice Problem2. What is the % concentration of sugar in a 591ml bottle of Gatorade?
C=?m= 35gV = 591ml
C= 𝑚
𝑉=
35𝑔
591𝑚𝑙
35𝑔
591𝑚𝑙=
𝑥𝑔
100𝑚𝑙
5.92%
Rearranging the Equations
Rearranging the Equation to solve for Mass
m=CV
Example
Gabrielle wants to make 125ml of a 8g/L saline solution. How much salt will she need to use?
C= 8g/Lm= ?V = 125ml
= 0.125L
m=CV
m=1g
m=8𝑔
𝐿𝑥0.125𝐿
Rearranging the Equation to solve for Volume
V=𝑚
𝐶
Example
What is the maximum volume that Marcus can make of an 8% solution of chocolate milk if he uses 24g of Nesquik powder?
C= 8%m= 24gV = ?
V=𝑚
𝐶
V=300ml
V=24𝑔
8𝑔/100𝑚𝑙=24𝑔
𝑥100𝑚𝑙
8𝑔
Example
What is the maximum volume that Marcus can make of an 8% solution of chocolate milk if he uses 24g of Nesquik powder?
C= 8%m= 24gV = ?
C=𝑚
𝑉=
8𝑔
100𝑚𝑙
V=300ml
C=8𝑔
100𝑚𝑙=24𝑔
𝑋𝑚𝑙
OR
Dilutions
Drink too sweet! What do you do?
Reducing the concentration of a solution by the addition of solvent
What is Dilution?
1 g of solute in 1 L of waterC= 1g/L
3 L of water
1 g of solute in 4 L of waterC= 0.25g/L
What’s happening to:-Solute?-Solvent?-Concentration?
• When you are diluting a substance
the amount of solute remains the
same
• The volume of solvent increases
• Therefore the concentration
decreases
Dilution
Formula
C1V1 = C2V2
Remember: mass remains the same!
Practice ProblemIzaah had 50ml of 20g/L solution of Kool-Aid. She found it to be too sweet so she added another 50ml of water. What is the final concentration (g/L)?
V1 = 50mlC1 = 20g/L
V2 = 50ml + 50ml = 100mlC2 = ?
C1V1 = C2V2
= 0.05L
= 0.1L
(20g/L)(0.05L) = C2(0.1L)
C2 = 1𝑔/𝐿
0.1= 10g/L