Gen chem equilibrium question

[Kratoz24x]

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So this problem is from the ACS book. And it's not that I don't know how to do it, but rather the method the DAT would take to solve it.

A mixture of 2 mol of co and 2 mol h20 mixed in a 10L flask. Kc = 4. What is the molar concentration of h2 in equilibrium?
Co + h20 = co2 + h20

B. .4 M
D. .13

So I set up the ice chart. Everything is cool. The answer I got was .4. The answer the book got was .13. Instead of dropping the x in the problem, they kept it and simplified it. So if a similar question gets on the dat should I try simplifying first?

 

[Impulse155]

So this problem is from the ACS book. And it's not that I don't know how to do it, but rather the method the DAT would take to solve it.

A mixture of 2 mol of co and 2 mol h20 mixed in a 10L flask. Kc = 4. What is the molar concentration of h2 in equilibrium?
Co + h20 = co2 + h20

B. .4 M
D. .13

So I set up the ice chart. Everything is cool. The answer I got was .4. The answer the book got was .13. Instead of dropping the x in the problem, they kept it and simplified it. So if a similar question gets on the dat should I try simplifying first?

Nvm it is balanced

 

[ikecarus]

I would say... don't drop the x because if you look at the answer choices, most of them are large enough values to make a difference when you subtract them from the reactants to get the reactant's final value (IDK if that makes sense). I doubt that the DAT expects you to do a lot of work with small numbers on the gen chem section because there aren't any calculators to use, so the x value should be large enough to be easy to work with.

I kept the x in the problem and found that you could take the square root of both sides of the equilibrium equation:

4 = x^2/(0.2-x)^2

So if you take the square root of both sides you get:

2 = x/0.2-x

Which is easy enough to work with. Hopefully that helps? 🙂

 

[Kratoz24x]

Haha yeah. It makes sense. But come test day, if I see a problem like that and I solve it both ways. And both the answers are on the screen, I'm legit just gonna walk out.

Thanks for the help guys