1. ChemSolutions

3. They all contain the same number of particles (atoms, molecules or ions) BUT HOW MANY PARTICLES.......? 602,000,000,000,000,000,000,000 approximately !!! and usually written as

4. 6.02 x 10 23 and called Avogadro's Constant (L)

5. 6.02 x 10 23 particles = 1 mole

6. CALCULATIONS IN CHEMISTRY A mole is an amount of substance. ONE MOLE of ANYTHING contains an Avogadro Number of particles (atoms, molecules or ions) 6.02 x 10 23 particles = 1 mole of substance

7. To find the number of moles we need to know the relative formula mass (Mr) of a substance: Relative formula mass = Relative atomic masses (Ar)

8. Eg. What is the Mr of water (H 2 O) Ar (H) = 1 Ar(O) = 16 Mr (H 2 O) = 1+1+16 = 18 MOLAR MASS (H 2 O) = 18g/mole

9. Find the Mr of the following : Cl 2 CH 4 NaCl CaCO 3

10. Find the Mr of the following : Cl 2 35.5 +35.5 = 70.0 CH 4 12 + (4x1) = 16 NaCl23 + 35.5 = 58.5 CaCO 3 40 + 12 + (3x16) = 100

11. Moles and Mass Conversion Formula is: MOLES = MASS___________ (n) RELATIVE FORMULA MASS

12. Example 1 How many moles of magnesium atoms are in 6g of magnesium metal? m = 6g Ar = 24 n = m Ar = 6/24 = 0.25 moles

13. Example 2 How many moles of substance are present in 10g of calcium carbonate? n = m Mr = 10/100 = 0.1 moles m = 10g Mr = (40 + 12 + 48) = 100

14. Example 3 How many moles of substance are present in 585g of sodium chloride? m = 585g Mr = (23 + 58.5) = 58.5 n = m Mr = 585/58.5 = 10 moles

15. Example 4 What is the mass of 0.01 moles of copper sulphate (CuSO 4 )? m = ? g Mr = (64 + 32 + (4x16)) = 160 m= n x Mr = 0.01 x 160 = 1.6 g

16. Example 5 8.8g of a gas contains 0.2 moles of gas molecules. What is the Relative Formula Mass (Mr) of the gas? What could the gas be? m = 8.8 g Mr = ? n = 0.2 Mr= m n = 8.8/0.2 = 44 Possibly CO 2

17. Molar mass from molecular formulae 1. Calculate the molar masses of the following: (a) P 4 O 10 (b) Al 2 (S0 4 ) 3 (c) (NH 4 ) 2 CO 3 (d) K 4 Fe(CN) 6 (e) NH 4 Fe(SO 4 ) 2.12H 2 O

18. Mass to mole conversions 2. How many moles of substance are present in the following? (a) 0.250 g of calcium carbonate (b) 5.30 g of anhydrous sodium carbonate (c) 5.72 g sodium carbonate-10- water crystals

19. a) 284 g/mole b) 342 g/mole c) 96 g/mole d) 368 g/mole e) 482 g/mole a) 0.0025 b) 0.05 c) 0.02 ANSWERS