Solving this chemistry is a little bit hard because the question didn't give some important detailed.
So first, there are a couple problems with your question.
We will just need to know which direction will it proceed to reach equilibrium.
Your expression for Kc (and Qc ) for the reaction should be:
Kc = [C] / [A] [B]^2
You have not provided a value for Kc, so a value of Qc tells you absolutely nothing. Qc is only valuable in relation to a numerical value for Kc. If Qc = Kc, then the reaction is at equilibrium. If Q < K, the reaction will form more products to reach equilibrium, and if Q > Kc, the reaction will form more reactants.
We have Kc = 4.2 x 10^-2 (given but missing in the question)
and When the balanced equation for this reaction is:
PCl5(g) ↔ PCl3(g) + Cl2(g)
so, according to the Kc formula:
Kc = the concentration of products / the concentration of the reactants
so, to get the concentration of the reactants in equilibrium, the concentration of the products / the concentration of the reactants should equal the Kc value which is given in the question (missing in your question).
So by substitution in Kc formula:
Kc = [PCl3]*[Cl2] / [PCl5]
4.2 x 10^-2 = 0.18 * 0.25 /[PCl5]
∴[PCl5] = 0.18*0.25 / 4.2x10^-2 = 1.07
So the concentration of the reactants in equilibrim = 1.07
Correct answers:
<span>Nuclear fission and fusion both affect the nucleus of an atom.
</span><span>The final products of fission and fusion are elements that are different than the original.
</span><span>Fission occurs mostly with elements heavier than lead on the periodic table.</span>
Answer: It takes 3.120 seconds for the concentration of A to decrease from 0.860 M to 0.260 M.
Explanation:
Integrated rate law for second order kinetics is given by:
k = rate constant = 
= initial concentration = 0.860 M
a= concentration left after time t = 0.260 M

Thus it takes 3.120 seconds for the concentration of A to decrease from 0.860 M to 0.260 M.
Answer:
<h2>The answer is 4.0 g/mL</h2>
Explanation:
The density of a substance can be found by using the formula

From the question
mass = 40 g
volume = 10 mL
The density of the object is

We have the final answer as
<h3>4.0 g/mL</h3>
Hope this helps you