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.

Starter1. 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, Fe2O3.Carbon monoxide, CO.

Aims1. Discuss alloys and their uses.

2. Work through examples of percentage composition calculations.

3. Work through examples of empirical formula calculations.

AlloysThe 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.

Uses of alloys

Name of alloy Metals present Uses

Brass Copper and zinc Door handles

and fittings.

Bronze Copper and Tin Statues

Solder Tin and Lead Joining metals together.

Stainless Steel Iron, Chromium and Nickel.

Cutlery, kitchen sinks.

Percentage CompositionIt 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 compoundX 100

For example:

1. Work out the percentage of iron in iron (III) oxide.

==112

160 X 100 70%

STEP 1: Formula Fe2O3 or (Fe3+)2(O2-)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 100STEP 4: % of iron in compound = mass of iron in compound

mass of compound

For example:Ammonium nitrate, NH4NO3, is used as a fertiliser. Find the percentage composition of nitrogen in this compound.

==28

80 X 100 35%

STEP 1: Formula NH4NO3

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 100STEP 4: % of N in compound = mass of N in compound

mass of compound

Percentage Composition Questions1. Calculate the percentage of hydrogen in ammonium

nitrate, NH4NO3.

2. Calculate the percentage of oxygen in ammonium nitrate, NH4NO3.

3. Calculate the percentage of hydrogen in water.

4. Calculate the percentage of sulphur in sulphur dioxide.

5%

60%

11.1%

50%

Empirical FormulaThe empirical formula of a compound gives the simplest ratio of the atoms present in that compound.

For example, ethane has the molecular C2H6.

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 CH3.

The empirical formula is obtained by calculating the simplest ratio of the atoms present in the compound.

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 Na2S1O4, or simply Na2SO4.

Step 1:

Elements

Step 2: Mass

Step 3: RAM

Step 4: No. of moles

Step 5: Divide by smallest moles

Na S O

1.84 1.28 2.56

23 32 16

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

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 Fe2O3.

Step 1:

Elements

Step 2: Mass

Step 3: RAM

Step 4: No. of moles

Step 5: Divide by smallest moles

Fe O

4.48 1.92

56 16

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

Questions on Empirical Formula1. 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.

Al2O3

CH3

PbI2