Reacting gas volumes - a level chem

What volume of oxygen reacts with 0.24cm3 of methane, CH4, at 298K and 100kPa?
CH4 + 2 O2 —-> CO2 + 2 H2O

Can someone please explain and work out a answer ? I don’t understand it.. thanks

Reply 1

Keels25

16

I'm a little rusty on A-level chem but I think this is what you need to do. (Also, do you mean 0.24dm^3 rather than 0.24cm^3?)

So you need to use the molar gas volumes equation e.g. n = v/24

(298K is equivalent to room temperature (~20 degrees celsius); 100kPa is equivalent to room atmospheric pressure - so you meet the conditions to use this equation).
You have balanced the equation correctly so that is a good start. Here are the steps:

1. Find moles of CH4 using n = v/24

2. Find moles of O2
You know from the balanced equation that CH4 reacts with O2 in a 1:2 ratio (CH4 : O2) so you can multiply moles of CH4 by 2 to get moles of O2.

3. Calculate volume of O2 by multiplying moles O2 by 24 (v=nx24)

Hopefully you can get to an answer! :smile:

Reply 2

CalypsoXenoo

OP

13

Original post by Keels25

I'm a little rusty on A-level chem but I think this is what you need to do. (Also, do you mean 0.24dm^3 rather than 0.24cm^3?)

So you need to use the molar gas volumes equation e.g. n = v/24

(298K is equivalent to room temperature (~20 degrees celsius); 100kPa is equivalent to room atmospheric pressure - so you meet the conditions to use this equation).
You have balanced the equation correctly so that is a good start. Here are the steps:

1. Find moles of CH4 using n = v/24

2. Find moles of O2
You know from the balanced equation that CH4 reacts with O2 in a 1:2 ratio (CH4 : O2) so you can multiply moles of CH4 by 2 to get moles of O2.

3. Calculate volume of O2 by multiplying moles O2 by 24 (v=nx24)

Hopefully you can get to an answer! :smile:

Hi thanks for your reply :smile:

and no I did mean cm3 not dm3
I followed your instructions and this is what I got :

CH4 :
n=v/24
0.24 / 24 = 0.01

O2:
0.01*2 = 0.02

0.02*2 = 0.48cm3

I think I have the right answer so thank you but you said room temp is 20 degrees celcius and if I do 289 - 273 I get 25 degrees celcius ? . Thanks for your reply :smile:

Reply 3

Keels25

16

Original post by CalypsoXenoo

Hi thanks for your reply :smile:

and no I did mean cm3 not dm3
I followed your instructions and this is what I got :

CH4 :
n=v/24
0.24 / 24 = 0.01

O2:
0.01*2 = 0.02

0.02*2 = 0.48cm3

I think I have the right answer so thank you but you said room temp is 20 degrees celcius and if I do 289 - 273 I get 25 degrees celcius ? . Thanks for your reply :smile:

Sorry I meant 25!!