First off, thanks for the help on the other problems...

For the reaction, A(g) + 2 B(g) <==> 2 C(g), Kc = 1 x 10-10 at 25°C. Which of the following statements is true?

1. Delta n = +1
2. The concentration of the products is greater than the concentration of the reactants.
3. The reaction is favored in the reverse direction.
4. The value of Kp will be larger than the value for Kc.

1 is false because delta n = -1.
4 is false because Kp = 4.087e-12 (which is smaller than Kc)

I believe it is not favored in the reverse direction... but then how would I know if the concentrations of the products are greater than that of the reacants?

1 is false.
2 is false. Kc=(C)2/(A)*(B)2.
With K = 10-10, the only way to get a number smaller than 1 is for the products to be small and the reactants to be large.
4 is false as you have said.
3 is correct. Same reasoning as 2. Products are small and reactants are large which means the reactants are favored and that means the reaction goes in the reverse direction (ALTHOUGH, with a double arrow, I wonder exactly what is meant by "the reverse direction--technically I don't know that there is a reverse direction). The answer would have been better stated as "the left side is favored over the right side." The intent of the problem, however, is for the answer to be 3.

To determine if the concentrations of the products are greater than the concentrations of the reactants, you need to compare the stoichiometric coefficients of the reactants and products in the balanced equation. In this case, the balanced equation is A(g) + 2 B(g) <==> 2 C(g).

Since there are more moles of reactants (A and 2 moles of B) compared to the moles of product (2 moles of C), the concentrations of the reactants will be greater than the concentrations of the products. Therefore, statement 2 is false.

Statement 3, "The reaction is favored in the reverse direction," is true. This is because the value of the equilibrium constant, Kc, is very small (1 x 10^-10). Small values of Kc indicate that the reaction favors the reactants over the products. In other words, the reverse reaction (A(g) + 2 B(g) <== 2 C(g)) is favored over the forward reaction (A(g) + 2 B(g) ==> 2 C(g)).

Statement 1 is false because the change in moles (delta n) is actually -1, not +1. For the forward reaction, the total moles of reactants (A and 2 B) is 3, and for the product (2 C), it is 2. The difference between the two is 3-2, which equals -1.

Statement 4 is false as you correctly pointed out. The value of Kp (the equilibrium constant expressed in terms of partial pressures) is smaller than the value of Kc. In this case, Kp is given as 4.087 x 10^-12, which is smaller than Kc (1 x 10^-10).

So, the correct statement is 3. The reaction is favored in the reverse direction.