Question

Kc=1. The initial concentrations are A = 0M, B = 0M, C=10M.

A+B --> C

calculate the reaction quotient.

(c)/(a)(b) = 10/0 .. is the answer zero?

Answer 1

No, 10/0 is an indeterminate value. You can prove that to yourself.
10/0 = 0 but 0*0 = 0 which isn't 10.
10/0 = 1 but 1*0 = 0 which isn't 10.
10/0 = 5 but 5*0 = 0 which isn't 10.
10/0 = 1,000 but 1000*0 = 0 which isn't 10. etc.
The bottom line to the answer of 10/0 = any number you pick because any number you choose will have that number * 0 and that will be zero and not 10. The math profs may not like my explanation; they probably have an elegant proof that I don't know. But this will give you the idea.

Answer 2

well if it is undefined, which way would the equilibrium shift?

Answer 3

C is too large; a and b are too small so it will shift to the left.