1. After completing these lessons you should be able to : Balanced equations show the mole ratio(s) of reactants and products. The molar volume is the same for all gases at the same temperature and pressure. Calculations involving molar volume. Determination of quantities of reactants and/or products using balanced equations and moles. The molar volume (in units of litres mol-1 ) is the same for all gases at the same temperature and pressure. The volume of a gas can be calculated from the number of moles and vice versa. Determination of quantities of reactants and/or products using balanced equation and:  gram formula masses (GFM) and mass  moles  concentrations and volumes of solutions  masses of solutes  molar volumes and volumes for gaseous reactions The concentration of a solution can be expressed in mol l-1. Balanced equations can be used in conjunction with concentrations and volumes of solutions and/or masses of solutes to determine quantities of reactants and/or products. The volumes of reactant and product gases can be calculated from the number of moles of each reactant and product.

2. b) Calculation of the mass or volume of products Learning intention Learn how the theoretical mass or volume of product can be calculated from the balanced reaction equation.

3. Equimolar amounts of substances contain equal numbers of elementary entities CopperWaterSodium chloride FormulaCuH2OH2ONa + Cl - 1mole63.5g18g58.5g Elementary entitiesAtomsMoleculesFormula units 1 mole contains6.02x10 23 atoms6.02x10 23 molecules 6.02x10 23 formula units

4. Worked example 1. Calculate the number of atoms in 6 g of carbon. 1 mole  6.02 x 10 23 Carbon atoms 12g  6.02 x 10 23 Carbon atoms 6 g  ( 6 / 12 ) x 6.02 x 10 23 = 3.01 x 10 23 Carbon atoms The Mole and Avogadro’s constant

5. Worked example 2. How many molecules are in 6g of water? = 2 x 10 23 molecules Avogadro’s constant of molecules1 Mole of water  18 g6.02 x 10 23 molecules  6 g(6/18) x 6.02 x 10 23 

6. Worked example 3. Calculate the number of atoms in 4 g of bromine. 1 mole  6.02 x 10 23 Br 2 molecules 160g  (2 x 6.02 x 10 23 ) Br atoms 4 g  ( 4 / 160 ) x 1.204 x 10 24 = 3.01 x 10 22 bromine atoms The Mole and Avogadro’s constant

7. Worked example 4. Calculate the number of sodium ions in 71g of sodium sulphate (Na + ) 2 SO 4 2- 1 mole  6.02 x 10 23 Formula units 142g  (2 x 6.02 x 10 23 ) Na + ions 71 g  ( 71 / 142 ) x 1.204 x 10 24 = 6.02 x 10 23 sodium ions The Mole and Avogadro’s constant

8. Calculations for you to try. 1.How many atoms are there in 0.01 g of carbon ? 2. How many oxygen atoms are there in 2.2 g of carbon dioxide? 3.Calculate the number of sodium ions in 1.00g of sodium carbonate. 4. Calculate the number of molecules in 25.5g of ammonia. 5. A sample of the gas dinitrogen tetroxide, N 2 O 4, contained 2.408 x 10 22 oxygen atoms. What mass of dinitrogen tetroxide was present?

9. 1.How many atoms are there in 0.01 g of carbon ? 5.02 x 10 20 C atoms

10. 2. How many oxygen atoms are there in 2.2 g of carbon dioxide? 6.02 x 10 22 O atoms

11. 3.Calculate the number of sodium ions in 1.00g of sodium carbonate. 1.14 x 10 21 Na + ions

12. 4. Calculate the number of molecules in 25.5g of ammonia. 9.03 x 10 23 molecules

13. 5. A sample of the gas dinitrogen tetroxide, N 2 O 4, contained 2.408 x 10 22 oxygen atoms. What mass of dinitrogen tetroxide was present? 0.92 g

14. 1. The mass of 1 mol of sodium is 23 g. What is the approximate mass of one sodium atom? A 6 × 10 23 g B 6 × 10 –23 g C 3.8 × 10 –23 g D 3.8 × 10 –24 g C

15. 2. In which of the following pairs do the gases contain the same number of oxygen atoms? A 1 mol of oxygen and 1 mol of carbon monoxide B 1 mol of oxygen and 0.5 mol of carbon dioxide C 0.5 mol of oxygen and 1 mol of carbon dioxide D 1 mol of oxygen and 1 mol of carbon dioxide D

16. 3. The Avogadro Constant is the same as the number of A molecules in 16 g of oxygen B electrons in 1 g of hydrogen C atoms in 24 g of carbon D ions in 1 litre of sodium chloride solution,concentration 1 mol l –1. B

17. From previous studies You should be able to Write Formulae Calculate percentage composition Calculate empirical formulae Calculate the number of moles in a given mass Calculate the number of moles of solute dissolved in a solution

18. Reacting Masses Accurately weigh a crucible Add approx 1.2g of Mg ribbon and reweigh Place the crucible and lid in a silica triangle. Heat gently at first then more strongly. Lift the lid with tongs from time to time to admit more oxygen, but not enough to let out the magnesium oxide.

19. Reacting masses When the reaction is complete, the magnesium will not glow more brightly when the lid is raised Allow the crucible to cool Reweigh the crucible

20. Calculations Using the balanced equation calculate the mass of MgO you would expect to be formed? 2Mg + O 2 → 2MgO

21. Reacting masses What mass of zinc sulphate will be produced on adding 6.0g zinc to excess sulphuric acid? 14.9g

22. Reacting masses What mass of sodium carbonate will react completely with 100cm 3 of nitric acid concentration 1 mol l -1 ? 5.3g

23. The Mole A mole is that amount of substance which contains as many ‘elementary particles’ as there are carbon atoms 12g of carbon-12. Fe Cu Sn I 2 55.8 g 63.5g 118.7g (126.9 x 2) = 253.8g One mole of an element is the relative atomic mass expressed in grams. One mole of an compound is the formula mass expressed in grams.

24. n = mass/GFM n= 18/12 n= 1.5 moles 1 mole Carbon ↔ 12g (18/12) x 1 ↔ 18g = 1.5 moles How many moles in 18g of carbon? You can calculate the number of moles (n) in a substances