Unit V: The Mole

1. Percent Composition What’s a Mole? Empirical & Molecular Formulae Molar Mass Unit V: The Mole Dilutions Molar Volume Molar Concentration Density & Molar Volume

2. Density of a Gas at STP • Recall that density is a measure of a substance’s massdivided by the volume it occupies So what is the density of argon gas at STP? HINT: list all the things you know about Argon at STP

3. The Heart of the Mole Conversion Sheet Number of Particles Mole (mol) Density of a gas at STP: Volume of a gas at STP (L) Mass (g)

4. Practice Using Density with Molar Volume What is the density of mustard gas (C4H8Cl2S) at STP?

5. Practice Using Density with Molar Volume An unknown gas is leaking from the chemical supplies room. After harnessing some of the gas, we find that it has a density of 3.16g/L. What is the gas?

6. The Heart of the Mole Conversion Sheet Number of Particles Mole (mol) volume of a solid or liquid (L) Density of a gas at STP: Volume of a gas at STP (L) Mass (g)

7. Practice with Regular-Old Density Questions How many mercury atoms are in 4.64µL of liquid mercury? (density=13.6g/mL)

8. Concentrations of Solutions: Molarity • In chemistry, we have a special way of expressing the concentration of (typically aqueous aka water-based) solutions. • “This soft drink is 10% sugar” – 10% of its mass? 10% of its volume? 10% of it’s weight? 10% of the molecules are sugar molecules? Not specific enough • We compare the concentrations of solutions by expressing the number of moles of soluteper litre of solvent • For example, if I poured 1.6 moles of calcium carbonate into 2.0 liters of water, I’d have: CaCO3 solution • We refer to this as molar concentrationor molarity, and has units of M

9. The Heart of the Mole Conversion Sheet Molarity Number of Particles Mole (mol) volume of a solid or liquid (L) Density of a gas at STP: Volume of a gas at STP (L) Mass (g)

10. Practice with Molarity Questions The NaCl content of ocean water can be approximated by mixing a salt shaker’s worth of table salt (4 moles) into 8 litres of water. What is the molarity of ocean water?

11. Practice with Molarity Questions Sensory deprivation chambers are filled with highly concentrated salt solutions to allow people to float in them. Preparing a sensory deprivation chamber will involve pouring 360kg of MgSO4 into a 750L tank. What is the MgSO4 molar concentration of a sensory deprivation tank?