[1QWK96GT]

Hey everybody. I am trying to solve some of these equations my teacher gave us to do.

1) The initial concentrations of A, B, and C are 1.1 M, 2.2 M, and 3.3 M respectively and the value of K is 1.3x10^3 at 25celsius.
a. Is this system at equilibrium?
b. If not, which way will it shift?
A(aq) + B(aq)  C(aq) + D(l)

Now for a.) I think they are equal because both arrows show the reaction going both ways?

For b.) I believe it is equal so this does not apply?

We briefly went over these in class there must be something I am missing.

Thanks,

[Corribus]

How the reaction is written doesn't make a bit of difference.  Are you familiar with the reaction quotient, Q?

[1QWK96GT]

I just looked it up its the reaction of products/reaction of reactants?

Also now I think that it is in fact not at equilibrium because of the liquid on one side. Which will cause it to shift to the left?

[Borek]

I just looked it up its the reaction of products/reaction of reactants?

Not "reaction of products" - product of concentrations of products in correct powers over product of reactants in correct powers.

Also now I think that it is in fact not at equilibrium because of the liquid on one side. Which will cause it to shift to the left?

If something is in a separate phase (as solid or liquid) its concentration (more precisely activity) is assumed to equal 1.

Try to write the quotient for this particular reaction.

[1QWK96GT]

Okay,
A=1.1M
B=2.2M
C=3.3M

It does not give me D for some reason.

1.1M+2.2M=3.3M Thats for A+B

3.3 + ? For d= 3.3M

Divide the two 3.3/3.3=1

Compare Q to K
K=1.3x10^3
Q=1

So K>Q

So it will shift to the right?

[Borek]

Reaction quotient is not a SUM.

http://www.chem.purdue.edu/gchelp/howtosolveit/Equilibrium/Reaction_Quotient.htm

[Corribus]

Here's a quick remedial lesson:

The equilibrium constant for a reaction xA + yB  zC + rD is:

[tex]K = \frac{[C]^z[D]^n}{[A]^x[ B]^y}[/tex]

Where here, the concentrations are concentrations once equilibrium has been reached.  In reality, we should use chemical activities, but a good approximation is that the activities are equal to the molar concentrations, except for pure liquids and solids, which are assigned activities (and hence "concentrations") = 1.  This is why they didn't give you a value for D.

Q, the reaciton quotient, is obtained by using the real concentrations for a system at a given moment of time.  By computing Q and comparing it to K, you can then determine which direction the reaction will proceed from the given starting point.

[Corribus]

Sorry, typo: the reaction should be xA + yB  zC + nD