Question

How many moles of ethylene (C2H4) can react with 12.9 liters of oxygen gas at 1.2 atmospheres and 297 Kelvin?

C2H4(g) + 3O2(g) yields 2CO2(g) + 2H2O(g)

I have a test later today, please show me how to do this so I'll know what to do on the test. Thank you. :)

Answer 1

I'm pretty sure this is a PVNRT problem. Do you know the ideal gas law formula?

Answer 2

Yes

Answer 3

Okay, well the first thing you need to go is find out how many moles of Oxygen you have, using the ideal gas law formula

Answer 4

Can you show me how to do that?

Answer 5

I think so, one sec let me look

Answer 6

I attempted it by plugging it into the formula before but I just don't think I got the right answer

Answer 7

You should know the formula if you have a test later :s but it's really easy to remember! It's PVNRT. Or PV = nRT
where
p = pressure (atm)
v = volume (L)
R = gas constant
n = moles (mol)
t = temperature (T)

Answer 8

So, use the values given in the problem to solve for n, which equals the number of moles of Oxygen gas. What value did you get?

Answer 9

I got 0.634 moles

Answer 10

Okay awesome. So there's 0.634 moles of Oxygen. Since you have a chemical equation and the moles of Oxygen, do you think you sort of know how to get to the moles of C2H4?

Answer 11

That's where I get lost lol

Answer 12

That's okay. That's where most people get lost. So, at this point we have to use dimensional analysis. Just a fancy word of saying to get from one thing to another. My high school chem teacher used to call it train-and-caboose

Answer 13

You have to use the chemical equation to determine the ratio. So, for every 3 mol of Oxygen there's 1 mol of C2H4

Answer 14

make sure to cross out your units

Answer 15

Ok thank you, I'll try it :)

Answer 16

Okay! Practice makes perfect! Let me know if you have anymore questions

Answer 17

Thanks!

Answer 18

Ok, sorry I'm really tired haha. How am I supposed to plug it in?

Answer 19

@sjg13e

Answer 20

What do you mean? Can you clarify? Plug in what? Do you mean the ideal gas law formula or dimensional analysis?

Answer 21

dimensional analysis

Answer 22

Oh okay, well that's a little different. The only way to really understand it is by doing practice problems, but I generally use this sort of thinking:

Answer 23

heres a link that might help http://www.katmarsoftware.com/articles/railroad-track-unit-conversion.htm

Answer 24

Ohh I see, thank you so much