[themonk]

I do not need an answer for the whole question, but just how to start it. Though I will write the whole question down:

A feed mixture consisting of 30% CO and 70% H2 is passed over a CuO-ZnO catalyst bed maintained at 500K what is the lowest operating pressure that would allow 40% conversion of the limiting reactant in the methanol synth reaction?
CO+2H -> CH OH
= -90 kJ/mole
= -25 kJ/mole
Assume Ideal gas and that is independent of T

Now my problem is setting up the question.
I believe the limiting reactant is CO because moles of H2 over moles of CO is 2 (using stoich values) and moles of H2 over moles of CO using the feed percentages (.7/.3) is 2.333 and since 2.33 is larger than 2 CO is the limiting reactant (page 120 of Elementary Principles of Chemical Processes / Rousseau).
I set up a chart with the initial feed, change and the final feed.

	CO	H2	CH3COH	Total
Initial	.3|	.7|	0|	1|
Change	-.3x|	-.7x|	+x|	|
Final	.3-.3x|	.7-.7x|	x|	1|

Something is wrong with the chart, and I believe it is the initial feed. That's where I need the help. And what do I consider the conversion? Do I set x equal to 40%? or equal to .40?

 But after doing this, I can figure out the y (amount of each component), and then the K (equilibrium constant). Since $$ K = K_v \cdot K_p = K_y \cdot P^n /$$ and $$ K _v /$$ is 1 at Ideal gas, I can find that $$ K = P^n \cdot K_y /$$

I can figure out the rest using other equations for K since I have change of enthalpy and change of gibbs free energy.

But figuring out the beginning, ie K_y is the confusing part.

[DevaDevil]

I believe the limiting reactant is CO because moles of H2 over moles of CO is 2 (using stoich values) and moles of H2 over moles of CO using the feed percentages (.7/.3) is 2.333 and since 2.33 is larger than 2 CO is the limiting reactant

correct

Something is wrong with the chart, and I believe it is the initial feed.

the initial is fine, what is wrong is the change. Use the stoechiometric coefficients here.

And what do I consider the conversion? Do I set x equal to 40%?

you set your CO_end as 60% of CO_start