Solution Concentration

Context

•Both molecular and ionic compounds can dissolve it water

•We can calculate the moles of something if we know the mass…

•How much are dissolved in moles per litre?

Dilute Solutions

Small quantity of solute per unit volume of

solution.

Concentrated Solutions

Large quantity of solute per unit volume of

solution.

ConcentrationThe concentration of a solution is the quantity

of solute in a solution.

C = quantity of solutequantity of solution

% Concentration

•This format is common on household and drugstore products▫Ex: Vinegar is reported at 5% acetic acid▫Ex: Hydrogen peroxide is 3%▫What does this mean?

Three types•v/v % (when solute is a liquid)

Vsolute x 100%ml/100ml

Vsolvent

•m/v % (when solute is a solid)msolute x 100%

g/100mlVsolvent

•m/m % (when both solute & solvent are solids)msolute x 100% g/100gmsolvent

Everyday Examples

•Vinegar is 5% v/v acetic acid▫5 mL of CH3COOH in 100 mL

vinegar

•Hydrogen peroxide is 3% m/v▫3 g of H2O2 per 100 mL of solution

•Yogurt is 2% m/m▫2 g of milk fat per 100 g yogurt

Example•Milk fat is present in milk. Whole milk

usually contains about 3.25% m/V milk fat. If you drink a 250mL glass of milk, what mass of fat have you consumed?

% m/v =msolute x 100% vsolvent

3.25 =msolute x 100% 250mL

msolute = 8.13 g of milk fat

ppm• Parts per million • Can also have ppb, ppt• Useful for reporting very small quantities• Often used in ecology and toxicology• Look for it on your bottled water• 1 ppm = 1mg/1L• 1 ppm = 1mg/1kg

▫ppm = 1 drop in a bath tub▫ppb = 1 drop in a swimming pool▫ppt = 1 drop in a 1000 swimming pools

E.g what is the molarity of a 250 mL solution that contains 2.00 g of NaOH?

Concentrations in Chemistry•Molar concentration (molarity)

▫Moles of solute dissolved in one liter of solution▫Units: mol/L (or lazy chemists sometimes use M)▫[ ] is molar concentration

C n

V n = 2.00 g

40.00 g/mol

= 0.0500 mol

C = 0.0500 mol

0.250 L

= 0.200 mol/L

M = 40.00 g/mol

m = 2.00 g

V = 0.250 L

n = ?

C = ?

Practice

•P. 305 # 1-3•P. 308 # 5,7•P. 310 # 10, 11•P. 316 # 19a,c,e, 20a,c,e, 21-23