[myoplex11]

A + B -> C + D (reversible reaction)

a 2L container contains 1 mol of C, 1.6 mol of D, 0.8 mol of A snd 0.8 mol of B. Calculate the equillibrium composition of the reaction. Kc =0.065

I think C and D are forming A and B because there is higher concentration of C and D. So equillbrium concentrations will be C = 0.5 -x
D =0.800 -x , A = 0.400 + x, B = 0.400+x and then i can sovle for x by plugging these values into my equillibrum expession and setting it equal to Kc(.0065) I my approach correct? 

[Donaldson Tan]

Your approach is correct. However, do not be surprised if X is negative in some cases.