Reaction Quotient Practice Problems
Initially, equal amounts of reactants and products are added to a reaction vessel. Which of the following is correct for the Qc of the reaction?
True or False: When Qc > Kc, the reaction will not shift in any direction because the reaction is already in equilibrium.
True or False: When Qc < Kc, 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 (Kp) 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, Qc, of the reaction?
The following reaction SO2(g) + Cl2(g) ⇌ SO2Cl2(g) has an equilibrium constant Kc = 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 Kc = 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 Kc = 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 < Kc if Kc = 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 Kc 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 Kp 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) + CO32-(aq) Kc = 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), Kc = 0.0132.
A sealed container with the gases at equilibrium at 298 K contains PN2O4 = 0.512 atm and PN2O = 0.0607 atm. A second container, under the same temperature, contains PN2O4 = 0.163 atm and PN2O = 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:
Cl2(aq) + HClO2(aq) + H2O(l) ⇌ 3 H+(aq) + 2 Cl-(aq) + ClO3-(aq) ; Kc = 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+] = 1.55 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:
PCl3(g) + Cl2(g) ⇌ PCl5(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?