Question

The partial pressure of CH4(g) is 0.175 atm and that of O2(g) is 0.250 atm in a
mixture of the two gases.

a. What is the mole fraction of each gas in the mixture?

i know Pt = Pa + Pb

and Pa = XaPt

do i use those here?

Answer 1

@Kryten do you know this?

Answer 2

yep you use those equations... so first you sum up the pressures and then divide individual pressures with summed up pressure and you will get percentage of each pressure in mixture

Answer 3

ohhh yeah i see \[X_A = \frac{P_A}{P_T}\]

Answer 4

xa is the mole fraction right?

Answer 5

yap

Answer 6

lol i was thinking i need \[n_A \; \text{and}\; n_B\] to solve it

Answer 7

what about this..

b. If a mixture occupies a volume of 10.5 L at 65ºC, calculate the number of
moles of each gas in the mixture.

what do i do then?

Answer 8

so you go like this:
0,175 + 0,25 = 0,425
and now
0,175 / 0,425 = 0,4117 = 41,17 % of CH4
and
1-0,4117 = 0,5883 = 58,83 % O2

Answer 9

wait...ratio is %?

Answer 10

isnt it like something-over-something?

Answer 11

no ratio isnt % but that is how you calculate percentage lol

Answer 12

ohhh. so the ratio would just be 0.175/0.425 or 0.4117, etc?

Answer 13

yep if im not still sleaping that is right :)

Answer 14

so then what about b

b. If a mixture occupies a volume of 10.5 L at 65ºC, calculate the number of
moles of each gas in the mixture.

what do i do there?

Answer 15

ok so now you need to calculate amount of mixture in moles:
pV=nRT--> n= pV/RT = 0,161 mol
(watch for units in pV=nRT !!! they must be in K, m3, Pa...)
and now you have
X= n/n(sum) --> n = X * n(sum)
n(CH4)= 0,4117 * 0,161 mol = 0,06628 mol

Answer 16

where did you get 0.161 again? is it given or solved?

Answer 17

solved from pV=nRT
p= 0,425 atm
V= 10,5 L
T=65 °C

Answer 18

0.425 is the total right?

Answer 19

yep 0,425 is the total from a. part of the task

Answer 20

why should the units be K, m3 and Pa...shouldnt it be K, L and atm?

Answer 21

you always need to calculate in standard units! they give you in nonstandard units so you need to recalculate! thats part of the solving!
R = 8,314 J mol-1 K-1 so to cross out you need to have temperature in K pressure in Pa and V in m3

Answer 22

wait i thought \[R = 0.0821 \frac{L \cdot atm}{K \cdot mol}\]

Answer 23

those are the standard units i know...

Answer 24

i dont see what you have written [Math Processing Error][Math Processing Error] is all i see

Answer 25

refresh

Answer 26

you are from US arent you?!
well take a look at this:
http://en.wikipedia.org/wiki/International_System_of_Units
there you got all standard units but you in US still use nonstandard units like F for temperature etc.

Answer 27

no im not

Answer 28

ok, calculate how you know just if you get right result... :)

Answer 29

i got 0.1607

Answer 30

so what happened next?

Answer 31

this is the total mole right...so what's the individual mole?

Answer 32

@Kryten ?

Answer 33

never mind i got it