1. Molality (m) A concentration that expresses the
moles of solute in 1 kg of solvent
Molality (m) = moles of solute
1 kg solvent

2. Units of Molality 2.0 m HCl = 2.0 moles HCl 1 kg solvent

3. Molality Calculation NaOH is used to open stopped sinks, to treat
cellulose in the making of nylon, and to
remove potato peels commercially.
If 4.0 g NaOH are used with 500. g of water, what is the molality (m) of the solution?

4. Calculating Molarity = 0.20 m NaOH
1) 4.0 g NaOH x 1 mole NaOH = 0.10 mole NaOH
40.0 g NaOH
2) 500. g x 1 kg _ = kg water
1000 g
mole NaOH = mole NaOH
0.500 kg water kg water
= 0.20 m NaOH

5. Calculating Molarity
A glucose solution is made with 2.0 kg water and 72 g glucose (C6H12O6). If glucose has a molar mass of 180. g/mole, what is the molality of the glucose solution?
1) 0.20 m
2) 5.0 m
3) 36 m

6. Solution
A glucose solution is made with 2.0 kg water and 72 g glucose (C6H12O6). If glucose has a molar mass of 180. g/mole, what is the molality of the glucose solution?
1) 72 g x 1 mole x = m
180. g kg

7. Molality & Grams & Volume
What is the molality of a solution prepared by mixing 3.0 moles NaOH with sufficient solvent to make a total mass of 400 g?
1) 12 m
2) 10.7 m
3) 300 m

8. Solution 2) 3.0 mol x 40 g = 120 g solute 1 mol
mass of solvent = 400 g total – 120 g solute = 280 g solvent
m = mol
0.280 kg
m = 10.7 m