How do the theoretical and actual masses of hydrocarbon reactions compare?

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Discussion Overview

The discussion revolves around the comparison of theoretical and actual masses in hydrocarbon combustion reactions, specifically focusing on methane, ethane, and propane. Participants explore discrepancies between expected and observed product masses in a chemistry lab simulation.

Discussion Character

  • Homework-related
  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant notes that the theoretical masses of products for the first reaction match the actual masses, but the same does not hold for the second and third reactions, raising questions about potential errors in the simulation or interpretation.
  • Another participant suggests that the stoichiometric equations are correct and points out that the proportion of hydrogen decreases with each hydrocarbon, which may affect product formation.
  • A participant expresses concern about the consistency of product masses across different reactions in the simulation, indicating that all reactions yield the same total mass of CO2 and H2O.
  • One participant requests more information about the online chemistry program to better understand the issue, speculating that a fixed amount of oxygen might be influencing the results.
  • Another participant agrees that the only variable seems to be the type of hydrocarbon, while the product masses remain unchanged, suggesting a possible limitation in the simulation.

Areas of Agreement / Disagreement

Participants do not reach a consensus regarding the reasons for the observed mass consistency across different hydrocarbon reactions. Multiple competing views about the influence of stoichiometry and simulation parameters remain present.

Contextual Notes

Participants express uncertainty about the specifics of the online chemistry program and its assumptions, including the potential for fixed reactant amounts and the presence of unaccounted products.

KYJelly
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Homework Statement



I'm currently doing a grade 11 chemistry lab online...So, there's three reactions that we have to interpret...

1. CH4 + 2 O2 ---> CO2 + 2 H2O
2. 2 C2H6 + 7 O2 ---> 4 CO2 + 6 H2O
3. C3H8 + 5 O2 ---> 3 CO2 + 4 H2O

Now, when I add the theoretical masses of the products for the first reaction (I'll spare the math for now), they add up to mass of the actual masses of the products in the first reaction. However, when I sum the theoretical masses of the products in the second reaction, I don't get the same sum as the actual masses in the second or third reaction. I notice that the actual masses for all three reactions (methane, ethane, and propane) are exactly the same. Is this just because the mass loss in the actual reactions are attributed to waste products and heat, or am I doing something terribly incorrect? Or is there something wrong with my simulation.

PS - I can provide my math, but I feel as though the program is working fine and that it's just that all hydrocarbon reactions of this sort yield the same product mass no matter what.
 
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Your stoichiometric equations appear perfectly OK.

I don't know if the point that is troubling you is just that in order 1, 2, 3 per mole of carbon you have a lower then lower proportion of hydrogen. So in that order, for the same amount of CO2 produced you produce less then less water H2O. The first compound is CH4, you could say the second is equivalent to CH3. Along the series you have fewer C-H bonds and more C-C bonds
 
No, the point that is troubling to me is that there's always the same mass of products in each reaction in the online experiment. For example, CH4 + 2 O2 ---> CO2 + 2 H20 yields 292 grams of CO2 and 179 grams of water, and 2 C2H6 + 7 O2 ---> 4 CO2 + 6 H2O yields 292 grams of CO2 and 179 grams of water, and C3H8 + 5 O2 ---> 3 CO2 + 4H2O also yields 292 grams of CO2 and 179 grams of water vapour in the online experiment.
 
Well I can't say more without seeing this online chemistry that is you are trying. If you could post it all verbatim perhaps I could help. Maybe reaction was with a fixed amount of oxygen?
 
Yeah, the only thing that changes is the hydrocarbon gas. Methane, Ethane, Propane. But, the masses of CO2 and H2O (as products) don't change.
 
Maybe it's about a fixed amount of oxygen, or maybe there is a product elemental carbon as you had in another problem, but unless I see the original text I'm just guessing what this is about
 

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