Determining rate constant and reaction order

[Aeon]

Homework Statement

CH3OCH3(g) ---> CH4(g) + H2(g) + CO(g)

The reaction is conducted at 777.15 K, at constant volume beginning with pure ether.

t(hours)  0    390  777  1195  3155  +inf
P (torr) 312   408  488  562    779   931

Determine the order of the reaction and approximate the rate constant.

Homework Equations

1) PV = nRT

The Attempt at a Solution

I know I need a number of moles. Pressure is related to moles as stated by equation 1.
Unless I assign an arbitrary value to V, I cannot calculate a value for n.

I have written this table:

                A --------------> 3B
t=0             a                   0
t              a-x                +3x
t=+inf         0                   3a

I know I have to convert P(tot) in P(ether) using:

P(tot) = (nA + nB) RT/V and
P(ether) = nA RT/V

But erm...
major brainfreeze. (as is usually the case when trying to study after a big meal lol!)


Thanks in advance.

 

[Aeon]

bump

I'm done with the rest of my HW. For some reason I can't get my head around this one (and another similar problem).

Can someone help me solve this problem? Please.

Thanks,
Aeon.