1. Molarity and Molality

2. Molarity (M) number of moles of solute (n) per liter (L) of solution
Molarity (M) = Moles of Solute
Liters of Solution
Note: Moles = Mass of Solute
Molar Mass of Solute

3. 1. What is the molarity of the solution if 3
1. What is the molarity of the solution if 3.0 mole of solute is dissolved in 12.0 L solution?
Given: Moles of Solute – 3.0 mole Liters of Solution – 12.0 L Formula: Molarity = Moles of Solute Liters of Solution Answer: M = Moles of Solute = 3.0 mole 12.0L = 0.25 M

4. 2. What is the molarity of a 400.0 mL solution containing 8.0 g NaOH?
Given: Mass of Solute – 8.0 g of NaOH Liters of Solution – mL Formula: Molarity = Moles of Solute Liters of Solution Answer: Moles = Mass of Solute Molar Mass of Solute = 8 g of NaOH ( g/mole) = 8 g NaOH 40 g/mole = 0.2 mole

5. Given: Molarity -. Liters of Solution – 400. 0 mL Moles of Solute – 0
Given: Molarity - ? Liters of Solution – mL Moles of Solute – 0.2 mole Formula: Molarity = Moles of Solute Liters of Solution Answer: M = Moles of Solute = 0.2 mole 0.4 L = 0.5 M
= 400mL X 1 L
1000mL
= 0.4L

6. 3. How many grams of Ca(OH)2 are needed to prepare an 800
3. How many grams of Ca(OH)2 are needed to prepare an mL solution of M concentration?
Given: Molarity – M Liters of Solution – mL Formula: Molarity = Moles of Solute Liters of Solution Answer: Moles = (Molarity) (Liters of Sol’n) = M (0.8 L) = moles
= 800mL X 1 L
1000mL
= 0.8L

7. Given: Mass of Solute –. Moles of Solute – 0
Given: Mass of Solute – ? Moles of Solute – mole Molar Mass – Ca(OH)2 = [40+([16x2]+[1x2])] = 74g/mole Formula: Moles = Mass of Solute Molar Mass of Solute Answer: Moles = Mass of Solute Mass of Solute = (Moles) (Molar Mass of Solute) = (0.012moles) (74g/mole) = 0.89 g

8. Molality (m)
as the number of moles of solute (n) per kilogram (kg) of solution
Molality (m) = Moles of Solute
Kilograms of Solvent
Note: Moles = Mass of Solute
Molar Mass of Solute

9. 1. What is the molality of a solution containing 0
1. What is the molality of a solution containing 0.46 mole of solute in 2.0 kg water?
Given: Moles of Solute – 0.46 mole Kilogram of Solvent – 2.0 kg Formula: Molality = Moles of Solute Kilogram of Solvent Answer: m = Moles of Solute = 0.46 mole 2.0kg = 0.23 m

10. 2. What is the molality of a solution containing 75
2. What is the molality of a solution containing 75.5 g Pb(NO3)2 in g water?
Given: Mass of Solute – 75.5 g Pb(NO3)2 Molar Mass = [207+([14]2)+([16]6)] = 331 g/mole Formula: Moles = Mass of Solute Molar Mass of Solute Answer: Moles = Mass of Solute = 75.5 g 331 g/mole = 0.23 moles

11. = 0.58 m Given: Molality – ? Moles of Solute – 0.23 moles
Kilogram of Solvent – g = 0.4kg
Formula: m = Moles of Solute
Kilogram of Solution
Answer: m = Moles of Solute
= 0.23 moles
0.4 kg
= 0.58 m

12. What mass of solute is needed to prepare each of the following solutions?  a L of M K2SO4   b. 375 mL of M NaF  
Calculate the molarity of each of the following solutions: a g KCl in mL solution  b g CaCl2 in L solution  
Calculate the molality of each of the following solutions: a g of NaCl dissolved in g of water b mol KCl in 16.0 mol of H2O