Reaction Quotient - Online Tutor, Practice Problems & Exam Prep

Initially, equal amounts of reactants and products are added to a reaction vessel. Which of the following is correct for the Q_c of the reaction?

Which of the following is true when Q_c = K_c?

True or False: When Q_c > K_c, the reaction will not shift in any direction because the reaction is already in equilibrium.

True or False: When Q_c < K_c, the reaction will shift in the direction of the reactants (to the left) in order to reestablish equilibrium.

Metal-halide lamps are a type of gas discharge lamp that contain tungsten electrodes doped with a metal M and an additional halide material (usually sodium iodide). The working temperature of the lamp varies between 1000-3000°C. At the working temperature of the lamp, sodium iodide dissociates to produce sodium and iodine atoms in gaseous form. 

NaI(s) → Na(g) + I(g)

The iodine atoms react with the metal M to produce gaseous MI₄. 

M(s) + 4 I(g) ⇌ MI₄(g) 

The equilibrium pressure of I(g) at 1200°C within the lamp is 0.0240 atm. Show quantitatively that the pressure of MI₄ at 1200°C will cause the reaction to go in the reverse direction at 2500°C (the pressure of I(g) is the same). Assume that for the theoretical metal M, the equilibrium constant (K_p) for the reaction is 210 at 1200°C and 15 at 2500°C. 

According to Le Chatelier's principle, how will the amount of solid zinc bromide change when the equilibrium of the following reaction is disturbed by removing Br^—? 

Zn²⁺(aq) + 2 Br^—(aq) ⇌ ZnBr₂(s)

How does the change in the amount of Br^— affect the reaction quotient, Q_c, of the reaction?

The following reaction SO₂(g) + Cl₂(g) ⇌ SO₂Cl₂(g) has an equilibrium constant K_c = 12.82 at 375 K. Calculate the concentration of each species once equilibrium is established if the initial concentrations are [SO₂] = 0.200 M, [Cl₂] = 0.150 M, and [SO₂Cl₂] = 0.600 M.

The equilibrium constant of the reaction P₂ + RQ → PR + PQ is K_c = 4. Which of the following diagrams depicts a reaction mixture of P₂, RQ, PR, and PQ at equilibrium? (P = pink, Q = green, R = gray)

Consider the following reaction 2 LM ⇌ L₂ + M₂ with an equilibrium constant of K_c = 0.25 The diagram below shows a mixture of the molecules L₂ (yellow), M₂ (black), and LM. Determine the correct statement about the mixture. 

For the reaction A₃ (g) + B₃ (g) ⇌ 3 AB (g), A and B atoms are represented as green and red colors in the diagram, respectively. Which box represents the system at Q < K_c if K_c = 1?

If 3.5 g of K₂CO₃ is added to 1.50 L of a solution containing 156 ppm of Fe²⁺, will Fe(OH)₂ precipitate form?

The K_c for the reaction at 820 °C is 1.02.

RbClO₃ (s) → RbO (s) + ClO₂ (g)

In a 5.60 L vessel at 820 °C, a mixture of 67.2 g RbClO₃, 23.4 g RbO, and 7.89 g ClO₂ was placed. As the system approach equilibrium, what happens to the amount of RbClO₃?

The reaction of PCl₃ with O₂ gas occurs readily as shown. 

2 PCl₃ (g) + O₂ (g) → 2 POCl₃ (g)

The equilibrium constant K_p for the reaction is 1.02 at 850 K. Will the reaction be at equilibrium when 0.018 atm PCl₃, 0.016 atm O₂, and 0.25 atm POCl₃ are mixed at 850 K? If not, does the mixture need to produce more products or reactants to attain equilibrium?

The following reaction has an equilibrium constant of 0.953 at 125 °C. 

N₂H₄ (g) → N₂ (g) + 2 H₂ (g)

At 125 °C, 3.00x10^-3 M N₂H₄, 4.50x10^-5 M N₂, 3.50x10^-5 M H₂ were mixed in a flask. Will the mixture reach equilibrium? If not, in which direction should the reaction proceed to reach equilibrium?

The three diagrams below depict three different reaction mixtures. The reaction takes place between H₂ (light grey molecules) and I₂ (violet molecules) and has an equilibrium constant of 45.9 at 490 °C.

H₂ + I₂ ⇌ 2 HI

Identify which mixture (if any) is at equilibrium.

Consider the reaction for the dissolution of Barium carbonate:

BaCO₃(s) ⇌ Ba²⁺(aq) + CO₃^2-(aq) K_c = 8.10 x 10^-8 at 25°C

Identify if additional solid barium carbonate is dissolved if it was added to a solution 2.0-L solution that already contains 15.02 g BaCO₃.

A sealed vessel initially contains [CO₂] = 0.215 M. Identify if more of the CaCO₃ will form or will some of the existing CaCO₃ decompose as equilibrium is reached in the reaction: CaCO₃(s) ⇌CaO(s) + CO₂(g), K_c = 0.0132.  

A sealed container with the gases at equilibrium at 298 K contains P_N2O4 = 0.512 atm and P_N2O = 0.0607 atm. A second container, under the same temperature, contains P_N2O4 = 0.163 atm and P_N2O = 0.0342 atm. The gases follow the reaction: N₂O₄(g) ⇌ 2 N₂O(g). Identify if the second reaction is at equilibrium. If it is not in equilibrium, calculate the equilibrium partial pressure of N₂O.

Given the following balanced equation:

Cl_2(aq) + HClO_2(aq) + H₂O_(l) ⇌ 3 H⁺_(aq) + 2 Cl^-_(aq) + ClO₃^-_(aq) ; K_c = 1.34×10⁶

A reaction mixture has the following concentrations of reactants and products:

[Cl₂] = 0.220 M; [HClO₂] = 0.250 M; [H⁺] = 0.0500 M; [Cl^-] = 0.0150 M; and [ClO₃^-] = 0.0111 M;

Determine the direction in which the reaction will proceed.

Consider the following electrochemical reaction taking place at 45 °C:

Cu_(s) + 2 Ag⁺_(aq) ⇌ Cu²⁺_(aq) + 2 Ag_(s)

The concentrations within the reaction cell are: [Ag⁺] = 1.25 M and [Cu²⁺] = 0.310 M

a. Write an expression for the reaction quotient (Q) for this reaction.

b. What is the value of the reaction quotient (Q)?

Consider the following reversibe reaction:

PCl_3(g) + Cl_2(g) ⇌ PCl_5(g) ; Kc = 0.18

A 1.00 L reaction vessel is loaded with 0.200 mol PCl₃, 0.250 mol Cl₂ and 0.140 mol PCl₅. When equilibrium is established, the vessel contains 0.0800 mol of PCl₅, what is the equilibrium concentration of Cl₂?

Consider the reaction for the dissolution of Barium carbonate:

BaCO₃(s) ⇌ Ba²⁺(aq) + CO₃^2-(aq) K_c = 8.10 x 10^-8 at 25°C

Identify if additional solid barium carbonate is dissolved if it was added to a solution 2.0-L solution that already contains 15.02 g BaCO₃.

A sealed container with the gases at equilibrium at 298 K contains P_N2O4 = 0.512 atm and P_N2O = 0.0607 atm. A second container, under the same temperature, contains P_N2O4 = 0.163 atm and P_N2O = 0.0342 atm. The gases follow the reaction: N₂O₄(g) ⇌ 2 N₂O(g). Identify if the second reaction is at equilibrium. If it is not in equilibrium, calculate the equilibrium partial pressure of N₂O.