1. Percentage Yield (again)

2. CaCO3 = CaO + CO2 FM: 100 56 44 Simple PERCENTAGE YIELD calculation
LIMESTONE (calcium carbonate) is used to make QUICKLIME (calcium oxide) for cement making
RAM
Ca 40
O 16
C 12
CaCO3 = CaO CO2
FM:
So, THEORETICALLY, 100 tonnes of limestone should produce 56 tonnes of quicklime.
BUT the ACTUAL YIELD is only 48 tonnes
So..the PERCENTAGE YIELD is only 48 x 100 = 87.5% 56
Why? – next slide

3. Very few chemical reactions have a yield of 100% because:
The raw materials (eg limestone) may not be pure
Some of the products may be left behind in the apparatus
The reaction may not have completely finished
Some reactants may give some unexpected products
Careful planning and design of the equipment and reaction conditions can help keep % yield high

4. The chemical reaction above produced 70g of Magnesium Oxide
Apply your knowledge:
RAM
Mg 24 Fe 56 C 12
O 16
2Mg O → 2MgO
RFM:
The chemical reaction above produced 70g of Magnesium Oxide

5. Trickier…….
Fe2O CO → 2Fe + 3CO2
320g of iron oxide made 200g of Iron. What is the percentage yield in this reaction?

6. Apply your knowledge:
RAM
Mg 24 Fe 56 C 12
O 16
2Mg O → 2MgO
RFM:
144g of Magnesium produced 170g of Magnesium Oxide. What is the percentage yield of this reaction?