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