1. Chemistry 5072 Avogadro’s Constant

2. Mass of 1 atom What is the mass of 1 proton? 1.67 X 10 -24 g o What is the mass of 1 neutron? 1.67 X 10 -24 g o What is the mass of one Hydrogen atom? 1.67 X 10 -24 g Because hydrogen atom has only one proton

3. Mass of 1 atom ctd… What is the mass of 1 carbon atom? 12 X 1.67 X 10 -24 g o What is the mass of 1 sodium atom? 23 X 1.67 X 10 -24 g

4. Molar mass He S Mg C 4242 32 16 24 12 6 Let’s take the mass number as the mass in gram, how many atoms are there? (i.e. how many atoms are there in 4g of He?)

5. Avogadro’s constant Well, you know that given the mass number in grams, there are 6 X 10 23 atoms/particles. 6 X 10 23 is a constant number and this is termed as Avogadro’s constant. 4g of He, 32g of S, 24g of Mg and 12g of C contain 6 X 10 23 particles. The mass which gives 6 X 10 23 particles is termed as Molar mass!

6. Mole One mole of any substance contains 6 X 10 23 of particles. Therefore, molar mass of Na is 23g/mol. How about molar mass of: a)Zn b)Si c)Ar d)Ca

7. Analogy Mass of 1 orange = mass of 1 apple = 10g If the basket can contains 2 apples and 2 oranges, what is the mass of the basket now? Mass of basket = 0g 40g If one container can take in 10 baskets, what is the mass of the container? 400g

8. Analogy ctd… Mass of 1 orange = mass of 1 apple = 10g If the basket can contains 5 apples and 5 oranges, what is the mass of the basket now? Mass of basket = 0g 100g If one container can take in 10 baskets, what is the mass of the container? 1000g

9. Analogy Mass of 1 orange = mass of 1 apple = 10g If the basket can contains 2 apples and 2 oranges, what is the mass of the basket now? Mass of basket = 0g 40g If 1 container can take in 10 baskets, what is the mass of the container? 400g proton neutron nucleus Mass number Molar mass Avogadro’s constantmole

10. Mole 1 mole of any substance contains 6 X 10 23 particles. How many particles are there in 2 moles of Na? 1.2 X 10 24 particles of Na o How many particles are there in 3 moles of C? 1.8 X 10 24 particles of C o How many particles are there in 0.25 of Ti? 1.5 X 10 23 particles of Ti

11. Mole ctd… If there are 4 X 10 23 particles of Mg, how many moles of Mg are there? 4 X 10 23 particles = 0.667 moles (3 sf) 6 X 10 23 particles If there are 1.5 X 10 22 particles of He, how many moles of He are there? 1.5 X 10 22 particles = 0.0250 moles (3 sf) 6 X 10 23 particles

12. Mole Number of particles X (6X10 23 ) ÷ (6X10 23 )