The Mole

1. The Mole

2. What is a mole? • A mole is the amount of a substance that contains as many atoms as there are atoms in 12 grams of pure carbon-12. • Its standardised (SI) units is mole (no surprise)

3. The Mole 1 dozen = 12 1 gross = 144 1 ream = 500 1 mole = 6.02 x 1023 There are exactly 12 grams of carbon-12 in one mole of carbon-12.

4. Avogadro’s number and the mole – periodic table • All the elements described on the periodic table has the mass number equivalent to the quantity of 1 mol • Carbon-12 is quite significant – all other elements are standardised against carbon-12.

5. Avogadro’s number is called “Avogadro’s Number” • Avogadro’s number describes how many atoms are there within a mole.

6. Mass and mole • Because of the relationship of the mole, we can write that • n = number of moles • m = mass (total mass), in grams • M = mass in mole

7. Sample Question • How many atoms are there within 1.5 mol of carbon?

8. Calculating number of particles • How many atoms are there within 1.5 mol of carbon?

9. Sample Question • How many moles is atoms worth?

10. Changing mass to mol • In a 6 g solution of pure carbon, how many carbon atoms does it contain?

11. Changing mol to mass • With a solution that has 2 mol of lithium, where the molecular mass of lithium is 7, find the actual mass of the solution

12. Molar mass • The molecular mass (m) of a substance is the mass of one molecule of that substance.

13. Practise • Give the molar masses of the following compounds: • 1. sodium fluoride -NaCl • 2. potassium hydroxide -KOH

14. Answer • (1 x 23 ) + (1 x 19 ) = 42 grams/mole of sodium fluoride • 2. (1 x 39) + (1 x 1) + (1 x 16) = 56 grams/mole of potassium hydroxide