# Chemistry Empirical Formula Question

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Thread starter 9 years ago
#1
Hi everyone,

Could I please ask for help with an empirical formula question I'm stuck on? Is there generally a best way to approach these questions? Thank you very much every1!

16g of hydrocarbon burn in excess oxygen to produce 44g of carbon dioxide. What is the empirical formula of the hydrocarbon?

(hint given was to work out the mass of carbon contained in 44g of CO2, which is the same as the mass of C in 16g of the hydrocarbon). (The answers say it is methane).

Thanks again. Struggling with these
0
9 years ago
#2
(Original post by vet_hopeful!_worried)
Hi everyone,

Could I please ask for help with an empirical formula question I'm stuck on? Is there generally a best way to approach these questions? Thank you very much every1!

16g of hydrocarbon burn in excess oxygen to produce 44g of carbon dioxide. What is the empirical formula of the hydrocarbon?

(hint given was to work out the mass of carbon contained in 44g of CO2, which is the same as the mass of C in 16g of the hydrocarbon). (The answers say it is methane).

Thanks again. Struggling with these
I've always used this rhyme (it's never let me down):

Percent to Mass
Mass to Mole
Divide by Small
Multiply 'till Whole.

Hope this helps!
1
9 years ago
#3
Mr of CO2 is 44. so 44g divide 44= 1 mol

1 mol of CO2 contain 1 mol of C
and because one mole of hydrocarbon react to form one mole of CO2

therefore the hydrocarbon should contain one mole of C too.

1 mole of CO2 made from 1 mole of hydrocarbon.

1 mole= 16g divide by Mr of hydrocarbon.
Rearrange, = 16g divide by 1= Mr=16

Mr of this hydrocarbon=16 and this hydrocarbon contain one mole of C

one mole of C=Mr of C=12
16-12=4
Hydrocarbon consist of carbon and hydrogen and Mr of H=1
so 4 hydrogen in this hydrocarbon.

therefore, one C and 4 Hydrogen=CH4=Methane.
1
9 years ago
#4
(Original post by vet_hopeful!_worried)
Hi everyone,

Could I please ask for help with an empirical formula question I'm stuck on? Is there generally a best way to approach these questions? Thank you very much every1!

16g of hydrocarbon burn in excess oxygen to produce 44g of carbon dioxide. What is the empirical formula of the hydrocarbon?

(hint given was to work out the mass of carbon contained in 44g of CO2, which is the same as the mass of C in 16g of the hydrocarbon). (The answers say it is methane).

Thanks again. Struggling with these
First, notice how the question says excess oxygen this means that it is complete combustion so CO2 and H2O are the products of the reaction

We have the mass of the CO2 so we can work out how many moles of CO2 we have

Spoiler:
Show
1 mole

This means that we had one mole of carbon atoms in the original hydrocarbon which has a mass of 12g

The hydrocarbon has a mass of 16g so that means the mass of the hydrogen is 16-12=4g

Next you'll need to work out how many moles of hydrogen you have and from there you have the empirical formula

Hope this helps. Need more depth just shout
0
Thread starter 9 years ago
#5
Thank you very much everyone, X
0
1 year ago
#6
This helped
0
X

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