Question

C. Consider the reaction 2C3H6 + 9O2 6CO2 + 6H2O. If the rate at which C3H6 is reacting is 0.40 mol liter−1s−1, then the rate at which

1. O2 is reacting is 1.6 mol liter−1s−1
2. CO2 is being formed is 0.40 mol liter−1s−1
3. H2O is being formed is 0.80 mol liter−1s−1
4. CO2 is being formed is 1.2 mol liter−1s−1
5. H2O is being formed is 1.6 mol liter−1s−1
6. none of the previous answers is correct

My thoughts:
I'm really struggling on this one. All I have figured out thus far is that C3H6 is a second order reaction, but I don't know if that even matters. Do I try to find the k value and then use that for the other ones? Any help in the right direction would be great! Thanks

Answer 1

You can go to this site and determine the order. I don't believe second order is correct.
https://en.wikipedia.org/wiki/Reaction_rate_constant#Units

I would do this as if it were a stoichiometry problem.
Calculate the rate for each. For example, for #1 (O2), it is
0.4 x (9 mols O2/2 mols C3H8) = 1.8 so 1 is not the answer. Etc.

Answer 2

Yeah, I was wrong, and it is a zero order reaction. If I do it that way, I get 4 to be an answer. Why can you do this as a stoichiometry problem? I guess I thought the rate orders were separate from the stoichiometric coefficients?