1. Starter 1.What is a blast furnace used for? 2. What 3 solid raw materials are added to the blast furnace? 3. Which other reactant is added to the blast furnace? 4. What is the name and formula of the main iron ore? 5. Which gas actually reduces the iron oxide? To extract iron from iron ore. Iron ore, coke and limestone. Hot air. Iron (III) Oxide, Fe 2 O 3. Carbon monoxide, CO.

2. Aims 1.Discuss alloys and their uses. 2.Work through examples of percentage composition calculations. 3.Work through examples of empirical formula calculations.

3. Alloys The properties of metals can be improved by making them into alloys. An alloy is a mixture of metals or of metals with non-metals. Alloys are usually made by melting the elements that make it up and then allowing it to cool until it has solidified.

4. Uses of alloys Name of alloyMetals presentUses BrassCopper and zincDoor handles and fittings. BronzeCopper and TinStatues SolderTin and LeadJoining metals together. Stainless SteelIron, Chromium and Nickel. Cutlery, kitchen sinks.

5. Percentage Composition It is important for chemists to know the percentage of each element in a compound. The equation we use for doing this is : % mass of element in a compound = Mass of element in compound Formula mass of compound X 100

6. For example: 1. Work out the percentage of iron in iron (III) oxide. = = 112 160 X 10070% STEP 1: Formula Fe 2 O 3 or (Fe 3+ ) 2 (O 2- ) 3 STEP 2: Formula mass(2 x Fe) + (3 x O) (2 x 56) + (3 x 16) = 112 + 48 = 160 STEP 3: Mass of Fe in formula 2 x 56 = 112 X 100 STEP 4: % of iron in compound = mass of iron in compound mass of compound

7. For example: Ammonium nitrate, NH 4 NO 3, is used as a fertiliser. Find the percentage composition of nitrogen in this compound. = = 28 80 X 10035% STEP 1: Formula NH 4 NO 3 STEP 2: Formula mass =(2 x N) + (4 x H) + (3 x O) (2 x 14) + (4 x 1) + (3 x 16) = 80 STEP 3: Mass of N in formula 2 x 14 = 28 X 100 STEP 4: % of N in compound = mass of N in compound mass of compound

8. Percentage Composition Questions 1.Calculate the percentage of hydrogen in ammonium nitrate, NH 4 NO 3. 2.Calculate the percentage of oxygen in ammonium nitrate, NH 4 NO 3. 3.Calculate the percentage of hydrogen in water. 4.Calculate the percentage of sulphur in sulphur dioxide. 5% 60% 11.1% 50%

9. Empirical Formula The empirical formula of a compound gives the simplest ratio of the atoms present in that compound. For example, ethane has the molecular C 2 H 6. The ratio of carbon atoms to hydrogen atoms is 2:6 and so the simplest ratio for this is 1:3. That means that the empirical formula for this is CH 3. The empirical formula is obtained by calculating the simplest ratio of the atoms present in the compound.

10. Q. Calculate the empirical formula of a compound containing 1.84g of sodium, 1.28g of sulphur and 2.56g of oxygen. Therefore the empirical formula is Na 2 S 1 O 4, or simply Na 2 SO 4. Step 1: Elements Step 2: Mass Step 3: RAM Step 4: No. of moles Step 5: Divide by smallest moles NaSO 1.841.282.56 233216 0.08/0.04 = 2 0.04/0.04 = 1 0.16/0.04 =4 n=1.84/23 = 0.08 n=1.28/32 =0.04 n=2.56/16 = 0.16

11. Q. 6.40g of iron oxide was found to contain 4.48g of iron. Calculate the empirical formula for the iron oxide We cannot have fractions of atoms and so therefore the empirical formula is Fe 2 O 3. Step 1: Elements Step 2: Mass Step 3: RAM Step 4: No. of moles Step 5: Divide by smallest moles FeO 4.481.92 5616 0.08/0.08 = 1 (1x2= 2) 0.12/0.08 = 1.5 (1.5x2=3) n=4.48/56 =0.08 n=1.92/16 =0.12

12. Questions on Empirical Formula 1.Calculate the empirical formula of the compound which contains 1.08g of aluminium combined to 0.96g of oxygen. 2.Calculate the empirical formula of the hydrocarbon 0.60g of carbon and 0.15g of hydrogen. 3.Calculate the empirical formula for the compound containing 6.21g of lead combined to 7.62g of iodine. Al 2 O 3 CH 3 PbI 2