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Topic: Combustion and empirical formulas please *delete me*  (Read 4778 times)

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justlearning

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Combustion and empirical formulas please *delete me*
« on: September 29, 2005, 02:17:38 AM »

Complete combustion of 19.48 g of a particular hydrocarbon yielded 62.93 g CO 2 and 20.61 g of H 2 O. What is the empirical formula of this hydrocarbon? (Enter your answer in the spaces below.)
Molar masses (in g mol -1 )
H, 1.00794    C, 12.011    O, 15.9994


the formula is c_h_. you have to find the blanks..
i tried working with this problem and it just left me with wrong answers.
i was hoping on help as to how to solve it..
this is what i tried

62.93g/molar mass c02 = 1 and     20.61g h20/molarmassh20= 1 , 19.48/molarmass02 = .6087
then i took the lowest number and divided each thing by it and my answer was wrong..

i also tried answreing the question without using any oxygen in the problem

so far my answers have been c1h4, c2h2, c1h1 and they all are wrong
PLEASE *delete me*!

Offline Mitch

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Re:Combustion and empirical formulas please *delete me*
« Reply #1 on: September 29, 2005, 02:24:40 AM »
Start by writing us a general chemical equation.
Most Common Suggestions I Make on the Forums.
1. Start by writing a balanced chemical equation.
2. Don't confuse thermodynamic stability with chemical reactivity.
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justlearning

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Re:Combustion and empirical formulas please *delete me*
« Reply #2 on: September 29, 2005, 02:27:11 AM »
h20 +c02 + 02 -----> c_h_

the thing is i am trying to find out the C_H_

Offline mike

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Re:Combustion and empirical formulas please *delete me*
« Reply #3 on: September 29, 2005, 02:37:16 AM »
You are burning your hydrocarbon in oxygen, rewrite the equation.

Also write down the molecular weights(mass) of CO2, H2O, O2.
There is no science without fancy, and no art without facts.

justlearning

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Re:Combustion and empirical formulas please *delete me*
« Reply #4 on: September 29, 2005, 02:41:10 AM »
hmm..i did all of that above...

thats all i can think of  though

Offline mike

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Re:Combustion and empirical formulas please *delete me*
« Reply #5 on: September 29, 2005, 02:45:33 AM »
No, your equation is wrong  ;)

It is your hydrocarbon CH + O2 ---> etc

also if you have worked out the molecular weights then how did you get 1, 1 and 0.6087 as your answers? these look wrong too, sorry! :-\
There is no science without fancy, and no art without facts.

Offline AWK

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Re:Combustion and empirical formulas please *delete me*
« Reply #6 on: September 29, 2005, 06:07:17 AM »
CxHy + zO2 =
hint
each carbon atom needs 1 molecule of O2
for 4 hydrogen atoms you need 1 molecule of O2
AWK

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