You are Here: Home >< A-levels

# F325 Chemistry/ Unifying Concepts Question watch

1. Eugenol is an organic compound of C, H and O.

A sample of 1.394g of eugenol was analysed by burning in oxygen to form 3.74g of CO2 and 0.918g of H2O. The relative molecular mass of eugenol was shown to be 164 using a mass spectrometer.

Calculate the molecular formula of eugenol.

- I know how to calculate the moles of carbon dioxide and water, however I don't know how to work out the mass of carbon and oxygen. I have been looking at different online sources and I have seen 12/44 multiplied 3.75

Is that because you're working out the proportion of mass of carbon out of carbon dioxide and then you multiply it by the moles of carbon dioxide....Can some one help me understand why when working out the mass of carbon you use the moles of co2. Please, step by step

2. I've not done the actual question. I will attempt it after.
But what i think you should do is find out moles of all of them. Then divide each one by the smallest one to find relative moles. Then the number in front of the CO2 would give the number of carbons and the number in front of the H2O x2 would give the hydrogens. Then add the molecular masses of the carbons and hydrogens that you found and take them away from 164. Then divide your answer by sixteen to get number of oxygen. Sorry if you can't understand it. Not very good at explaining. I will attempt it after then I'll put the answer that I get on here.
I very well may be wrong though.

Posted from TSR Mobile
3. My question is that how to you work out the mass of carbon, to do the empirical formula you need the mass of carbon I think it's 12/44 the carbon composition out of co2 then multiply by the mass of co2...i think I kind of get it but not 100%
4. The challenge is finding the mass of the individual elements.... the mass of carbon from the total mass of carbon dioxide
5. (Original post by ImNervous)
I've not done the actual question. I will attempt it after.
But what i think you should do is find out moles of all of them. Then divide each one by the smallest one to find relative moles. Then the number in front of the CO2 would give the number of carbons and the number in front of the H2O x2 would give the hydrogens. Then add the molecular masses of the carbons and hydrogens that you found and take them away from 164. Then divide your answer by sixteen to get number of oxygen. Sorry if you can't understand it. Not very good at explaining. I will attempt it after then I'll put the answer that I get on here.
I very well may be wrong though.

Posted from TSR Mobile
6. The way you were talking about is probably another method but I'm not too aware of what to do

Posted from TSR Mobile
7. Actually my way doesn't seem to work. Unless you wrote the question wrong.

Posted from TSR Mobile
8. Actually it does work. I read the question wrong.
You should get
C10 H12 O2

Posted from TSR Mobile
9. Hello......

Posted from TSR Mobile

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: February 6, 2016
Today on TSR

### Are you living on a tight budget at uni?

From budgets to cutbacks...

### University open days

1. University of Cambridge
Wed, 26 Sep '18
2. Norwich University of the Arts
Fri, 28 Sep '18
3. Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 29 Sep '18
Poll

## All the essentials

### Student life: what to expect

What it's really like going to uni

### Essay expert

Learn to write like a pro with our ultimate essay guide.

### Create a study plan

Get your head around what you need to do and when with the study planner tool.

### Resources by subject

Everything from mind maps to class notes.

### Study tips from A* students

Students who got top grades in their A-levels share their secrets