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Topic: Masses of Components in a Mixture  (Read 6982 times)

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Offline whitfi51

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Masses of Components in a Mixture
« on: September 16, 2012, 03:09:14 PM »
An organic liquid is a mixture of methyl alcohol (CH3OH) and ethyl alcohol (C2H2OH). A 0.220-sample of the liquid is burned in an excess of and yields 0.343 (carbon dioxide).

Set up two algebraic equations, one expressing the mass of carbon dioxide produced in terms of each reagent and the other expressing the mass of sample burned in terms of each reagent.
What is the mass of methyl alcohol (CH3OH) in the sample?

I've tried to solve this problem multiple ways and I'm just not getting the right answer. I don't think I really understand what I'm supposed to be doing at all. I want to actually understand what I'm doing.
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Offline sjb

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Re: Masses of Components in a Mixture
« Reply #1 on: September 16, 2012, 03:19:06 PM »
Quote from: whitfi51 on September 16, 2012, 03:09:14 PM
An organic liquid is a mixture of methyl alcohol (CH3OH) and ethyl alcohol (C2H2OH). A 0.220-sample of the liquid is burned in an excess of and yields 0.343 (carbon dioxide).

Set up two algebraic equations, one expressing the mass of carbon dioxide produced in terms of each reagent and the other expressing the mass of sample burned in terms of each reagent.
What is the mass of methyl alcohol (CH3OH) in the sample?

I've tried to solve this problem multiple ways and I'm just not getting the right answer. I don't think I really understand what I'm supposed to be doing at all. I want to actually understand what I'm doing.

Ethanol is C2H5OH. Can you write a balanced equation for the combustion of methanol, or ethanol?
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Offline whitfi51

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Re: Masses of Components in a Mixture
« Reply #2 on: September 16, 2012, 04:19:16 PM »
Yup I wrote one.

2CH3OH + 2C2H5OH + 9O2  :rarrow: 6CO2 + 10 H2O
 
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Offline Borek

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Re: Masses of Components in a Mixture
« Reply #3 on: September 16, 2012, 04:52:03 PM »
If there was mMe g of methanol, how many grams of CO2 were produced?
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Offline DrCMS

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Re: Masses of Components in a Mixture
« Reply #4 on: September 17, 2012, 05:03:19 AM »
Quote from: whitfi51 on September 16, 2012, 04:19:16 PM
Yup I wrote one.

2CH3OH + 2C2H5OH + 9O2  :rarrow: 6CO2 + 10 H2O

This is correct only if there are equimolar amounts of each.  It is very unlikely to be correct and that is probably why you have not got the right answer.

I assume from your question the sample was 0.220g of the mixture and it produced 0.343g of carbon dioxide.  Always ensure you use the correct units.

1) Set up a balanced equation for the combustion of methanol.
2) Set up a balanced equation for the combustion of ethanol.
3) Assuming there are x grams of methanol and y grams of ethanol set up and equation that releates x and y to the mass of carbon dioxide formed.
Solve for x and y
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