Finding out unknown moles and masses in the compound

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Dhamnekar Winod
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Finding out unknown moles and masses in the compound

Post by Dhamnekar Winod »

A 7.49g sample of compound of C, H, and O burns in presence of oxygen to produce 15.0g CO2 and 8.17g H2O. ?

What mass of Oxygen was present in original sample? What is this reaction equation?

Answer:- We Know mass of sample of compound = 7.49g,
15.0 g of CO2= 0.3409 M.
8.17g of H2O = 0.4534 M

I think the reaction is \(CH_2O(g) + O_2(g) \rightarrow CO_2(g) + H_2O(l) \)

Now, how to proceed further?
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
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ChenBeier
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Re: Finding out unknown moles and masses in the compound

Post by ChenBeier »

Why do you think its the right equation. Show your calculation.
According to the moles of CO2 and H2O the ratio C: H has to be 4:10. In Formaldehyde it is 1:2. So this can not be right.
The mass difference gives 15 g O2 from outside. Its 0.5 mol.
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Dhamnekar Winod
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Re: Finding out unknown moles and masses in the compound

Post by Dhamnekar Winod »

How did you compute the molar ratio of C:H as 4: 10 according to moles of CO2 and H2O? I am not saying the reaction stated in my original thread is correct. I just expressed my opinion.In the original question reaction is not given. You said the stated reaction is wrong. I agree.

Chemistry Professor on other chemistry education site has given the following answer:
mass of compound = 7.49 g

mass of CO2 = 15.0 g

moles of CO2 = 0.3409 moles

moles of C = 0.3409 moles(How is this computed?🤔)

mass of C = 4.0909 g

mass of H2O = 8.17 g

moles of H2O = 0.4535 moles

moles of H = 0.9070 (How is this computed?🤔)
mass of H 0.9142

mass of C+H = 5.01 g

mass of O = 2.48 g
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
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ChenBeier
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Re: Finding out unknown moles and masses in the compound

Post by ChenBeier »

You have 0.3409 mol of CO2 this is equal to the mole of C. Then you have 0.4535 mol of water this is equal to the double because water contain 2 H also 0.907 mol. That is what the proffessor also calculated.

So now you normilize these numbers. Set Carbon to 1 and divide the other. You get 2.66 for H. Now you multiply until the numbers almost not brocken. Multiply by 4 gives C 4 and H10.6 ~ 10, also C4H10

Then you do the same with the oxygen computed by the proffessor. You get almost 2.
So the formula is C4H10O2.
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