Chem 2 Ch. 14 Smarbook

Match each equilibrium constant symbol with its correct description. 1. Kc 2. Kp a) an equilibrium expressed in terms of the partial pressures of its components b) an equilibrium expression in terms of the concentrations of its components

Kc --> an equilibrium expression in terms of the concentrations of its components Kp --> an equilibrium expressed in terms of the partial pressures of its components

Given the following equilibrium data at a particular temperature: 2NO2Cl(g) ⇌ 2NO2(g) + Cl2(g) [NO2Cl] = 0.019 M, [NO2] = 0.041 M, and [Cl2] = 0.037 M calculate the value of Kc for the reaction at this temperature.

Kc = ((0.041)2(0.037))/(0.019)2 = 0.17

Calculate the equilibrium concentration of PCl3 for the equilibrium system represented below. PCl5(g) ⇌ PCl3(g) + Cl2(g); Kc= 62; [PCl5] = 0.00582 M, and [Cl2] = 0.731 M.

Kc = 62 = ([PCl 3](0.731))/0.00582 = 0.49 M

Select the correct expression for the equilibrium constant for the overall reaction in a multistep process.

Koverall = K1*K2*K3*...

Given the following reaction, which concentration terms appear in the numerator of the expression for Kc? CO(g) + H2O(g) ⇌ CO2(g) + H2(g)

[H2] [CO2]

If a reaction is said to "shift to the left" in response to a stress applied while at equilibrium, it means that the value of Q has become _____ than K as a result of the stress, & the system must produce higher _____ concentrations in order to reestablish equilibrium.

greater reactant

If the temperature of a system at equilibrium is increased, the system will shift to use up the excess heat, favoring the _____ reaction. A decrease in temperature causes more heat to be produced, favoring the _____ reaction.

endothermic exothermic

What is the correct expression for Kc for the reaction 2POCl3(g) ⇌ 2PCl3(g) + O2(g)?

([PCl 3]2[O2])/[POCl 3]2

An equilibrium in which all reacting species are in the same phase is a(n) ______ equilibrium mixture. a) aqueous b) homogeneous c) heterogeneous d) phase

b) homogeneous

Which of the following options correctly describe how a system at equilibrium will respond to a change in temperature? Select all that apply. a) A change in temperature will cause a change in Kc. b) If the forward reaction is exothermic, an increase in temperature causes a shift to the left. c) There are many reactions that will not undergo an equilibrium shift if the temperature is changed. d) If the forward reaction is endothermic, an increase in temperature causes a shift to the left.

a) A change in temperature will cause a change in Kc. b) If the forward reaction is exothermic, an increase in temperature causes a shift to the left.

Match the phrases below to form sentences that correctly describe the effect of temperature changes on reactions at equilibrium. 1. An endothermic reaction 2. An exothermic reaction 3. A decrease in temperature 4. An increase in temperature a) will shift to the right in response to an increase in temperature b) will cause an endothermic reaction to shift to the left c) will cause an exothermic reaction the shift to the left d) will shift to the right in response to a decrease in temperature

1. An endothermic reaction -->.will shift to the right in response to an increase in temperature 2. An exothermic reaction --> will shift to the right in response to a decrease in temperature 3. A decrease in temperature --> will cause an endothermic reaction to shift to the left 4. An increase in temperature --> will cause an exothermic reaction the shift to the left

The equilibrium constant Kc for a particular reaction is given by the expression [X]a/[Y]b. Match the components of this expression correctly for the balanced equation 3O2 (g) ⇌ 2O3 (g). 1. X 2. a 3. Y 4. b a) O3 b) 2 c) 3 d) O2

X --> O3 a --> 2 Y --> O2 b --> 3

Which of the following options correctly describes a heterogeneous equilibrium? a) An equilibrium system in which reactants and products are in different phases b) An equilibrium system in which all three phases of matter are present c) An equilibrium system in which the products are gases d) An equilibrium system in which reactants and products are in solution

a) An equilibrium system in which reactants and products are in different phases

Which of the following statements correctly describe how the addition of a catalyst will affect a system at equilibrium? Select all that apply. a) Equilibrium is unaffected. b) Addition of a catalyst causes the equilibrium to shift toward the products, increasing the reaction yield. c) A catalyst increases the value of K. d) The concentration of a catalyst appears in the numerator of the expression for K. e) A catalyst does not change the value of K.

a) Equilibrium is unaffected. e) A catalyst does not change the value of K.

Which of the following represent heterogeneous equilibria? Select all that apply. a) H2SO3(aq) ⇌ H2O(l) + SO2(g) b) BaCO3(s) ⇌ BaO(s) + CO2(g) c) H2(g) + Cl2(g) ⇌ 2HCl(g) d) H2(g) + I2(s) ⇌ 2HI(g)

a) H2SO3(aq) ⇌ H2O(l) + SO2(g) b) BaCO3(s) ⇌ BaO(s) + CO2(g)

Which of the following symbols for K denotes the equilibrium constant based on molar concentrations? a) Kc b) Km c) Kp d) KM

a) Kc

Which statement does NOT correctly describe a chemical system at equilibrium? a) No forward or reverse reaction is occurring b) Two reactions are occurring simultaneously c) There is no change in the concentration of reactants or products d) The forward & reverse reactions are occurring at the same time

a) No forward or reverse reaction is occurring

Which of the following statements correctly describe a chemical system at equilibrium? Select all that apply. a) The forward and reverse reactions occur at equal rates. b) There is no longer a change in concentration of reactants and products over time. c) The reactants are completely used up. d) Reactants are no longer reacting to form products. e) The concentrations of reactants and products are equal.

a) The forward and reverse reactions occur at equal rates. b) There is no longer a change in concentration of reactants and products over time.

The subscript "c" used in the symbol Kc indicates the concentrations of the products and reactants are expressed in _____. a) mol/L b) mm Hg c) atm d) mol/kg

a) mol/L

According to Le Chatelier's principle, when a stress is applied to a system at equilibrium, the system will _____. a) react in such a way as to minimize the disturbance b) remain in the stressed state c) exhaust the limiting reactant and go to completion d) return to its original equilibrium position

a) react in such a way as to minimize the disturbance

0.10 mol of NO(g), 0.050 mol of H2(g), and 0.10 mol of H2O(g) are placed in a 1.0-L container. These will react according to the balanced equation: 2NO(g) + 2H2(g) ⇌ N2(g) + 2H2O(g). Given that [NO] = 0.062 M at equilibrium, select all the options that correctly describe the steps required to calculate Kc for the reaction. a) the initial [N2] = 0 M b) if the change in [N2] = +x, then the change in [NO] = -2x c) [H2] at equilibrium = 0.050 - x d) x = (0.10-0.062)/2 = 0.019 e) Kc = ((0.019)(0.10)2)/(0.10)2(0.050)2)

a) the initial [N2] = 0 M b) if the change in [N2] = +x, then the change in [NO] = -2x d) x = (0.10-0.062)/2 = 0.019

0.20 mol of NO(g) is placed in a 1-L container with 0.15 mol of Br2(g). These will react according to the balanced equation 2NOBr(g) ⇌ 2NO(g) + Br2(g). Given that [NOBr] = 0.18 M at equilibrium, select all the options that correctly describe the steps required to calculate Kc for the reaction. a) the initial [NOBr] = 0 M b) x = 0.18/2 = 0.09 c) [NO] at equilibrium = 0.20 - x d) if the change in [Br2] = -x, then the change in [NOBr] = +2x e) Kc = (0.15)(0.20)/(0.18)2

a) the initial [NOBr] = 0 M b) x = 0.18/2 = 0.09 d) if the change in [Br2] = -x, then the change in [NOBr] = +2x

Which of the following statements correctly describe the equilibrium constant K? Select all that apply. a) Reactant concentrations are reflected in the numerator of the expression for K. b) K expresses a particular ratio of equilibrium concentrations of products and reactants. c) The value of K is characteristic of a particular equilibrium system. d) The expression for K has the general form [products]/[reactants]. e) The value of K for a particular reaction is the same under all conditions.

b) K expresses a particular ratio of equilibrium concentrations of products and reactants. c) The value of K is characteristic of a particular equilibrium system. d) The expression for K has the general form [products]/[reactants].

Which of the following correctly describes the relationship between the equilibrium constant K for a reaction and the rate constants for the forward and reverse reactions at equilibrium? a) Kc = kr*kf b) Kc = kf/kr c) Kc = kr/kf d) Kc = kf+kf

b) Kc = kf/kr

What does not change when the container volume of the equilibrium reaction shown below is decreased at constant temperature? 2NOBr(g) ⇌ 2NO(g) + Br2(g) a) The partial pressures of the components b) The value of KP c) The value of Q d) The concentrations of the components

b) The value of KP

In a homogeneous equilibrium, all components of the reaction are ______. a) Present in equal concentration b) Soluble in water c) In the same phase

c) In the same phase

What does the phrase "shift to the right" mean when describing the response of a system at equilibrium to a disturbance? Select all that apply. a) The reaction forms more reactants until the system reaches equilibrium again. b) The reaction uses up more products until a new equilibrium state is established. c) The concentrations of the products will increase until the system reaches equilibrium again. d) The reaction shifts toward the products until a new equilibrium state is established.

c) The concentrations of the products will increase until the system reaches equilibrium again. d) The reaction shifts toward the products until a new equilibrium state is established.

Which of the following statements correctly reflect Le Chatelier's principle? Select all that apply. a) After a system at equilibrium is disturbed, it will shift to counteract the disturbance and return to the same equilibrium position as before. b) When a system at equilibrium is disturbed, it can never reach equilibrium again. c) When a system at equilibrium is disturbed, Q ≠ K. d) When a system at equilibrium is disturbed, the system reacts to minimize the effect of the disturbance.

c) When a system at equilibrium is disturbed, Q ≠ K. d) When a system at equilibrium is disturbed, the system reacts to minimize the effect of the disturbance.

As a reaction proceeds, the value of Q _____. a) increases steadily until it reaches the value of K b) decreases steadily until it reaches the value of K c) increases or decreases, as necessary, until it reaches the value of K

c) increases or decreases, as necessary, until it reaches the value of K

For a given reaction, Kc is the equilibrium constant based on the molar _____ of reactants & products while Kp is the equilibrium constant based on the partial _____ of reactants & products.

concentration(s) pressure(s)

At a given temperature, the values of rate constants for the forward and reverse reaction are _____ and the ratio kf/kr is equal to the _____ constant for the reaction.

constant equilibrium

If the concentration of a reactant or product is changed in a system at equilibrium, what will happen to the value of K if the temperature remains constant? a) The value of K will increase if the reaction shifts toward the reactants. b) The value of K may increase or decrease, depending on the shift in equilibrium and the reacting species. c) The value of K will increase if the reaction shifts toward the products. d) The value of K will remain unchanged because the ratio of product to reactant concentrations at equilibrium does not change.

d) The value of K will remain unchanged because the ratio of product to reactant concentrations at equilibrium does not change.

The equilibrium constant is an expression of the ratio of ______ to ______ for a system at equilibrium. Multiple choice question. a) rates; concentrations b) rates; products c) reactants; catalysts d) products; reactants

d) products; reactants

Consider a gaseous reaction at equilibrium in a container with a moving piston. If the piston is moved so as to increase the volume of the container, the partial pressures of all of the gases in the container will _____. The equilibrium will shift in the direction that produces _____ moles of gas.

decrease more

If an equilibrium system contains gaseous reactants and/or products, a change in volume will cause a change in concentration and pressure. A decrease in volume will cause the system to shift in the direction that produces _____ moles of gas in total, whereas an increase in volume causes a shift in the direction that produces _____ moles of gas in total.

fewer more

If the value of K for the forward reaction is less than 1, the value of K for the reverse reaction is (greater/less) than 1.

greater

An equilibrium system that contains reactants and products in different phases is called a(n) _____ equilibrium system.

heterogeneous

If a system at equilibrium is disturbed by changing the concentration of a reactant or product, the equilibrium _____ will shift but the ratio of product to reactant will be _____ once the system reestablishes equilibrium. The value of K will be _____.

position the same unchanged

To construct the expression for the equilibrium constant Kc for a given reaction, the _____ concentrations are placed in the numerator & the _____ concentrations are placed in the denominator. Each term is then raised to the power of its stoichiometric coefficient from the _____ equation.

product reactant balanced

Substituting product and reactant concentrations into the equilibrium constant expression at any point in the progress of the reaction gives the reaction _____, also known as Q.

quotient

A system at equilibrium will respond to a disturbance by a shift in equilibrium position. A "shift to the left" indicates that the reaction proceeds toward the _____, whereas a "shift to the right" indicates that the reaction proceeds toward the _____.

reactants products

For any equilibrium reaction, the value of K for the reverse reaction is equal to the _____ of the value of K for the forward reaction.

reciprocal