Chemical Equilibrium Test

1. A reversible reaction _______.

2. Complete the statement below.

Equilibrium happens when _________.

3.  A system has reached chemical equilibrium. Which is true of the system?

4.  Which does not remain constant when a system is at dynamic equilibrium?

5.  Which of these does the equation below represent?

    I_2(s) ⇔  I_2(g)

6.  Which of the following is not an example of heterogeneous equilibrium?

I.     H₂O(l) ⇔ H₂O(g)

II.    C(s) + CO₂(g) ⇔ CO₂(g)

III.   N₂O₄(g) ⇔ 2NO₂(g)

IV.  C₂H₅OH(l) ⇔ C₂H₅OH(g)

V.   CaCO₃(s) ⇔ CaO(s) + CO₂(g)

7.  In the equilibrium constant expression below, what do the exponents represent?

8.  Which is true of the numerical value of the equilibrium constant, K_eq?

9.  Which represents K_eq for the equilibrium of the system shown below?

N_2(g) + 3H_2(g) ⇔ 2NH_3(g)

I.

II.

III.

IV.

V.

10.  If a chemical system at equilibrium is disturbed, the rates of the forward and reverse reactions are temporarily unequal. This is known as _____________.

Which is not true regarding the effects temperature changes have on a system at chemical equilibrium?

When a catalyst is added to a chemical system involving a reversible reaction, the catalyst __________.

Which is the correct equation for the quadratic formula?

I.

II.

III.

IV.

V.

Which is not true of a reaction quotient?

The following reaction is an example of homogeneous equilibrium:

 H₂(g) + I₂(g) ⇔ 2HI(g)

If the pressure is halved, by doubling the volume and the temperature remains constant, the equilibrium will _______.

A small amount of product is added to the equilibrium system below:

 H₂(g) + I₂(g) ⇔ 2HI(g)

 Predict the result.

Nitrogen and oxygen can react as follows:

Endothermic

N_2(g)  + O_2(g)  ⇔   2NO_{(g) ,}  DH = =180 kJ

Exothermic

If the temperature of the system is increased, 

The following systems are at equilibrium.

(i) CO₂(g) + 3H₂(g) ⇔ CH₄(g) + H₂O(g)

(ii) H₂(g) + I₂ (g) ⇔ 2HI(g)

(iii) N₂O₄(g) ⇔ 2NO₂(g)

(iv) N₂(g) + 3H₂(g) ⇔ 2NH₃(g)

Which of the systems will not be affected by a change in pressure?

Phosphorus pentachloride, PCl₅(g), undergo decomposition as shown:

PCl₅ (g) ⇔ PCl₃(g) + Cl₂(g)

The equilibrium expression for the reaction is

I.

II.

III.

IV.

V.

If the equilibrium shown below is heated at a constant pressure.

H₂(g) + I₂(g) ⇔ 2HI(g) + 65 kJ

What is most likely to happen?

How does homogeneous equilibrium differ from heterogeneous equilibrium?

Who proposed the Law of Chemical Equilibrium?  What is the Law of Mass Action?

An ICE table is useful to organize information about a chemical system. What does the acronym ICE stand for?

Phosphoric acid is found in fertilizers. The exothermic equilibrium reaction used to produce phosphoric acid from water and tetraphosphorus decaoxide is shown below.

P₄O_10(s) + H₂O_(l) ⇔ H₃PO_4(aq) + heat

 Based on Le Châtelier’s principle, explain two different ways that you could maximize yields in this equilibrium.

Phosphorous pentachloride is a fine grained powder, ranging in colour from colourless to pale yellow. It has a pungent odour. In the gaseous state it shows the following equilibrium:

 PCl₅(g) ⇔  PCl₃(g) + Cl₂(g)

Initially, a sample of phosphorus pentachloride is introduced to an empty vessel. If the equilibrium constant for the above reaction is 4.0 x 10^–4 and the equilibrium concentration of [PCl₅(g)] is 0.090 mol/L, the equilibrium concentration of [PCl₃(g)] is _______ mol/L.

Mountain climbers must take several weeks to get used to the reduced oxygen at high altitudes. The reduced oxygen is a result of the following equilibrium, where Hb represents hemoglobin, the protein that is responsible for transporting oxygen to the cells in the body.

Hb_(aq) + O_2(g) ⇔ HbO_2(g)

a) What happens to the equilibrium when a mountain climber is first introduced to the reduced oxygen?

b) Over time, a mountain climber’s body adjusts by producing more hemoglobin. How does this affect the equilibrium?

In the Haber-Bosch process of manufacturing ammonia, nitrogen is treated with hydrogen, which results in an exothermic reaction. An iron catalyst (Fe³⁺) is used in the process and aluminum oxide and potassium oxide are used as promoters. The following reactions takes place at 25 ^oC:

N₂(g) + 3H₂(g) ⇔ 2NH₃(g) + 92 kJ

Indicate the direction in which the equilibrium will shift when:

• temperature is increased.
• volume is increased.
• pressure is decreased.
• a catalyst is added.
• the concentration of N₂(g) is increased.
• helium gas is added at constant volume, so that the total pressure is increased.