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# Another GCSE Chemistry question!! STUCK! watch

1. Calcium oxide is made by the thermal decomposition of calcium carbonate

CaCO3 ---> CaO + CO2

a) Calculate the theoretical yield of calcium oxide that can be made from 15g of calcium carbonate, CaCO3.

b) The actual yield of calcium oxide is 7.2g. Calculate the percentage yield of calcium oxide.

Like last time, I have got an answer but still don't know if it is right!? My answer is in the spoiler. Thanks!!

Spoiler:
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a) 8.4g
b) 85.7%
2. a, Theoretical yield is found by working out the moles of the original reactants (in this case CaCO3) and then multiplying this by the formula mass of the product you want to make. (15/100 = 0.15 mol. 0.15 * 56 = 8.4g)

b, The percentage yield is found by dividing actual yield by theoretical yield. (7.2/8.4 = 85.7%)

So yep, you're correct!
3. (Original post by fliscia)
a, Theoretical yield is found by working out the moles of the original reactants (in this case CaCO3) and then multiplying this by the formula mass of the product you want to make. (15/100 = 0.15 mol. 0.15 * 56 = 8.4g)

b, The percentage yield is found by dividing actual yield by theoretical yield. (7.2/8.4 = 85.7%)

So yep, you're correct!
WOW!! Thank you very much!!!! I can finally work out theoretical yield and percentage yield thank you!!!!
WOW!! Thank you very much!!!! I can finally work out theoretical yield and percentage yield thank you!!!!

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