Answer:
D) [PCl5]=0.00765M,[PCl3]=0.117M,and [Cl2]=0.0.117M
Explanation:
Based on the reaction:
PCl₅(g) ⇄ PCl₃(g) + Cl₂(g)
And knowing:
Kc = [PCl₃] [Cl₂] / [PCl₅] = 1.80
When you add PCl₅ into a flask, this gas will react producing PCl₃ and Cl₂ until [PCl₃] [Cl₂] / [PCl₅] = 1.80
This could be written as:
[PCl₃] = X
[Cl₂] = X
[PCl₅] = 0.125M - X
<em>Where X represents the moles of PCl₅ that react, </em><em>reaction coordinate.</em>
Replacing in Kc expression:
[PCl₃] [Cl₂] / [PCl₅] = 1.80
[X [X] / [0.125 - X] = 1.80
X² = 0.225 - 1.80X
0 = -X² -1.80X + 0.225
Solving for X:
X = -1.9M → False solution, there is no negative concentrations
X = 0.11735M → Right solution.
Replacing, concentrations in equilibrium are:
[PCl₃] = X
[Cl₂] = X
[PCl₅] = 0.125M - X
[PCl₃] = 0.117M
[Cl₂] = 0.117M
[PCl₅] = 0.00765M
And right option is:
<h3>D) [PCl5]=0.00765M,[PCl3]=0.117M,and [Cl2]=0.0.117M</h3>
= 18.234 grams