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1. So this was a question on the June 2015 paper. I'm not terrible at maths but I still couldn't figure this out. Someone please explain this to me properly before I start crying:

Calculate the mass of cyclohexanol needed to obtain 10.0g if cyclohexane if the yield is 75%.
2. (Original post by slaya)
So this was a question on the June 2015 paper. I'm not terrible at maths but I still couldn't figure this out. Someone please explain this to me properly before I start crying:

Calculate the mass of cyclohexanol needed to obtain 10.0g if cyclohexane if the yield is 75%.
It's a 1 to 1 reaction.

In other words 1 mol of cyclohexanol makes 1 mol of cyclohexene (I'm assuming a typo)

Calculate mol of cyclohexene in 10g by dividing by the Mr

Then calculate the mass of cyclohexanol which has this number of moles

This value represents 75% so now scale up the mass to 100%
3. What exam board?

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1. the experimental yield(amount you obtained) is 10g
2. the theoretical yield (amount your supposed to get..'x')
3. yield=(experimental yield/Theoretical yield)X100
4. Therefore (10/x)X100=75
5. x=13.3g (that means you have put in enough cyclohexanol to make 13.3g of cyclohexane)
6. soo now u just calculate the number of moles of cyclohexane in 13.3g, that number of moles is equal to the number of moles of cyclohexanol put in (1:1 ratio)
7. then moles=mass/molar mass is used to calculate the mass of cyclohexanol in (the number of moles u found earlier)
THERE U GO!! it sounds a bit long but its quite easy just do like 2-3 sums of this type...keep repeating this until u completely understand it
hope i helped...i hated this question but now i love it... theres a similar one in the 2016 JAN Unit 3 IAL AS paper also just try that as well

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