CHEMICAL EQUILIBRIUM

Calculate the equilibrium constant (Kc) for the given reaction and tell whether equilibrium lies to the left or the right.

PCl₅ (g) ↔ PCl₃ (g) + Cl₂ (g)

Equilibrium concentrations are: [PCl₅] = 0.25 M, [PCl₃] = 9.7 × 10^-4 M, and [Cl₂] = 3.2 × 10^-3 M.

• 1.02 lies to the left

• 0.000012 lies to the left

• 1.02 lies to the right

• 0.000012416 lies to the left

What is the K_c expression for this reaction?
   2 NO_(g)  +  O_2(g) ⇌  2 NO_2(g)

• K_c = [NO₂]² / [NO]² [O₂]
• K_c =  [NO]² [O₂] / [NO₂]²
• K_c = [NO]² [O₂] [NO₂]²
• K_c = [NO₂]² / [NO]² +  [O₂]

When 0.40 mole of SO₂ and 0.60 mole of O₂ are placed in an evacuated 1.00–liter flask, the reaction represented below occurs.

2SO_{2 (g)} + O_{2 (g)} ↔ 2SO_{3 (g)}

After the reactants and the product reach equilibrium and the initial temperature is restored, the flask is found to contain 0.30 mole of SO₃. Based on these results, the equilibrium constant, Kc, for the reaction is

• 20

• 10

• 6.7

• 2.0

H₂(g)+Cl₂(g)⇌2HCl(g)

The forward reaction is exothermic. What will happen to the equilibrium if the temperature is increased?

• equilibrium shifts right

• equilibrium shifts left

• You cannot predict the effect

• no change

What is the equilibrium expression for: Fe₃O₄(s) + 4H₂(g) ⇌ 3Fe(s) + 4H₂O(g) K_c =

• [Fe]³ [H₂O]⁴  / [Fe₃O₄] [H₂]⁴
• [Fe₃O₄] [H₂]⁴ /  [Fe]³ [H₂O]⁴
• [H₂O]⁴ / [H₂]⁴
• [Fe] [H₂O] / [Fe₃O₄] [H₂]

What are the two factors to look for when determining if the reaction is at equilibrium?

• Forward reaction rate is faster than the reverse and concentrations are equal
• Forward and reverse reaction rates are equal and concentration is conctant
• Forward and revers reaction rates are equal and concentration is equal
• Forward reaction rate is faster than the reverse and concentration is equal

Predict whether the reaction will shift to the right, left or not be affected by an INCREASE in temperature

2H₂O₂ (g) ↔ 2H₂O (g) + O₂ (g) exothermic

• left

• right

• no effect

2SO₂(g)+O₂(g)⇌2SO₃(g)
Removing O₂(g) will

• shift equilibrium right
• shift equilibrium left
• increase pressure
• have no change

Consider the following system at equilibrium:

CH₄(g) + 2H₂O (g) ↔ CO₂ (g) + 4H₂O (g)

Suppose the concentration of CH₄ decreased, in which direction does the reaction shift to reestablish equilibrium?

• The reaction shifts to the left

• The reaction shifts to the right

For the reaction... N_{2 (g)} +  3 H_2 (g) ⇌ 2 NH_{3 (g)} If the pressure in the system is increased,  which substance(s) will increase in concentration?

• N₂  (as 2 mol gas  → 4 mol gas)
• H₂ (as 2 mol gas  → 4 mol gas)
• N₂ and H₂ (as 2 mol gas  → 4 mol gas)
• NH₃ (as 4 mol gas  → 2 mol gas)