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# hard question gcse watch

1. OK i think this is the right question
octane burns completely in air to give how much CO2?
114g of Octane burn completely what is the mass of CO2 produced?

Can't remember the formulas however the test gave us the Ar of each element, i worked out that the Mr of the octane was 114. When i worked out the Mr of CO2 by multiplying 44 by the number in front of the CO2, i think it was 8 This gave me the answer 352 g for the mass of CO2.

HOWEVER i thought after this you had to divide the 352 by 44 in order to give you 8g of CO2 produced? Looking at it now it seems really stupid what i did, is this answer wrong, should i have left it as 352g?
2. (Original post by thewebmaster)
OK i think this is the right question
octane burns completely in air to give how much CO2?
114g of Octane burn completely what is the mass of CO2 produced?

Can't remember the formulas however the test gave us the Ar of each element, i worked out that the Mr of the octane was 114. When i worked out the Mr of CO2 by multiplying 44 by the number in front of the CO2, i think it was 8 This gave me the answer 352 g for the mass of CO2.

HOWEVER i thought after this you had to divide the 352 by 44 in order to give you 8g of CO2 produced? Looking at it now it seems really stupid what i did, is this answer wrong, should i have left it as 352g?
Lets see...

C8H18 + 12½O2 ------> 9H2O + 8CO2
Mr=
114 + 400 --> 162 + 352

114g of C8H18 is 1 mole. So it'll make 8 moles of CO2. Either way, that's 352g, so you got it wrong

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