Question

is there any way to know if its products or reactants..?

The equilibrium constant for the gas phase reaction

N2 (g) + 3H2 (g) (2 arrows: one to right, one to left.) 2NH3 (g)

is Keq = 4.34 × 10^-3 at 300°C. At equilibrium, __________.

A) reactants predominate
B) only reactants are present
C) roughly equal amounts of products and reactants are present
D) only products are present
E) products predominate

Answer 1

yes.
Q = (NH3)^2/(N2)(H2)^3 = 4.34E-3

In general, A is true. For Q to be small, the numerator must be small and the denominator must be large. The only way you get that is for the products to be small and the reactants to be large(r).
It's easier to answer questions like this when the squared and cubed terms are missing (concns just to the first power) such as K = (A)/(B)(C); then only A would b true out of all of the possibilities given. B and D are never true. C is true, in the simpler K I mentioned above, when k = 1; it's tougher to work it out with the squared and cubed terms there. But you can make up a scenario where NH3 = 2 and (H2) + N2 = 2, then Q = 1/4 (1 for 1 of each, 1/4 for 2 of each, 1/9 for 3 of each, 1/16 for 4 of each etc BUT products are always decreasing with those numbers which still means products are less than reactants.

Answer 2

i understand a lot better now, thank you. someone tried to explain about k=1 and i just got more confused. thank you for taking the time to explain.

Answer 3

I have another question, if Keg was negative would it make a difference?