Chapter 14 LearnSmart
At a given temperature, the rate constants for the forward and reverse reaction remain ___ and the ratio kfkrkfkr is equal to the ___ constant for the reaction.
Blank 1: constant, the same, or unchanged Blank 2: equilibrium
For a reaction that is proceeding toward equilibrium in the reverse direction, product concentrations are _____ than their equilibrium values, and reactant concentrations are ______ than their equilibrium values. Under these circumstances, Q will be ______ than K.
greater; less; greater
An equilibrium in which all reacting species are in the same phase is a(n) ______ equilibrium mixture.
homogeneous
In a homogeneous equilibrium, all components of the reaction are ______.
in the same phase
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.
If the change in [Br2] = -x, then the change in [NOBr] = +2x. x = 0.1820.182 = 0.09 The initial [NOBr] = 0 M.
1.9 moles of HI are added to an evacuated, sealed 10.-L container and allowed to decompose according to the chemical equation: H2(g) + I2(g) ⇌ 2HI(g); Kc = 1.26 × 10−3
If the change in [H2] = +xH2 = +x, then at equilibrium [I2] = xI2 = x. The initial [HI] = 0.19 MHI = 0.19 M. Kc = 1.26 ×10−3 = (0.19 −2x)^2/x^2
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.
If the change in [N2] = +x, then the change in [NO] = -2x. x = 0.10−0.06220.10-0.0622 = 0.019 The initial [N2] = 0 M.
A sample of solid C is placed in a sealed reaction vessel containing 2.0 atm H2(g) and allowed to react according to the equation C(s) + 2H2(g) ⇌ CH4(g). At equilibrium the partial pressure of CH4 = 0.39 atm. Calculate KP for the reaction.
KP = 0.39/(2.0-0.78)2 = 0.26
A sample of solid C is placed in a sealed reaction vessel containing 2.0 atm H2(g) and allowed to react according to the equation C(s) + 2H2(g) ⇌ CH4(g). At equilibrium the partial pressure of CH4 = 0.39 atm. Calculate KP for the reaction.
KP = 0.39/(2.0−0.78)2= 0.26
Which of the following is the correct expression for the relationship between Kc and Kp?
KP = Kc(RT)Δn
Which of the following symbols for K denotes the equilibrium constant based on molar concentrations?
Kc
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?
Kc = kf/kr
Select the correct expression for the equilibrium constant for the overall reaction in a multistep process.
Koverall = K1 x K2 x K3 x
A gas cylinder at 500K is charged with PCl5 at an initial pressure of 1.66 atm. The PCl5 is allowed to decompose according to the following reaction: PCl5(g) ⇌ PCl3(g) + Cl2(g). The value of Kp for this reaction at 500K is 0.497. Which of the following options correctly reflect how to calculate the partial pressure of Cl2 at equilibrium? Select all that apply.
Kp = 0.497 = x21.66−xx21.66-x If the change in partial pressure of Cl2 = +x, then at equilibrium the partial pressure of PCl3 = x. The initial partial pressure of Cl2 = 0 atm.
As a reaction proceeds, the value of Q _____.
increases or decreases, as necessary, until it reaches the value of K
As a reaction proceeds toward equilibrium from reactants to products (i.e., from left to right as written), the value of Q is _____.
increasing
Which statement does NOT correctly describe a chemical system at equilibrium?
No forward or reverse reaction is occurring.
Given the following reaction, which concentration terms appear in the numerator of the expression for Kc? CO(g) + H2O(g) ⇌ CO2(g) + H2(g)
[CO2] [H2]
Given the following reaction, which concentration terms appear in the denominator of the expression for Kc? CFCl3(g) + HCl(g) ⇌ CCl4(g) + HF(g)
[HCl] [CFCl3]
What is the correct expression for Kc for the reaction 2POCl3(g) ⇌ 2PCl3(g) + O2(g)?
[PCl3]2[O2]/[POCl3]2
If the value of K for the forward reaction is less than 1, the value of K for the reverse reaction is _____ than 1.
greater
For a system at equilibrium, the equilibrium constant K expresses the ratio ____ of of the products and reactants at a particular ____.
lank 1: concentrations, pressures, concentration, or molarities Blank 2: temperature
The subscript "c" used in the symbol Kc indicates the concentrations of the products and reactants are expressed in _____.
mol/L
Given the balanced equation 2PbO(s) + O2(g) ⇌ 2PbO2(s), calculate the value of Δn.
-1
Which of the following statements correctly describe how an equilibrium system containing gases will respond to changes in volume and/or pressure, if the temperature remains unchanged? Select all that apply.
-If an inert gas is added there will be no effect on the equilibrium position. -If the volume is decreased, the reaction shifts in the direction that produces fewer moles of gas. -If the total number of moles of gas in the products and reactants is the same, a change in volume will not affect the equilibrium position.
Which of the following options correctly describe how a system at equilibrium will respond to a change in temperature? Select all that apply.
-If the forward reaction is exothermic, an increase in temperature causes a shift to the left. -A change in temperature will cause a change in Kc.
Which of the following statements correctly describe the equilibrium constant K? Select all that apply.
-The expression for K has the general form [products]/[reactants] -The value of K is characteristic of a particular equilibrium system. -K expresses a particular ratio of equilibrium concentrations of products and reactants.
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.
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.
0.49 M
Given the balanced equation CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g), calculate the value of Δn.
2
Given the following equilibrium data at a particular temperature: CH2O2(l) + CH4O(l) ⇌ C2H4O2(l) + H2O(l) [CH2O2] = 0.025 M, [CH4O] = 9.2 M, [C2H4O2] = 2.0 M, and [H2O] = 0.48 M calculate the value of Kc for the reaction at this temperature. Note that H2O is not the solvent in this reaction, and its concentration is included in the equilibrium constant expression.
4.2
Which of the following statements correctly describe how the addition of a catalyst will affect a system at equilibrium? Select all that apply.
A catalyst does not change the value of K. Equilibrium is unaffected.
Which of the following actions will NOT increase the total gas pressure inside a vessel containing the equilibrium reaction shown? CaCO3(s) ⇌ CaO(s) + CO2(g)
Adding CaO to the vessel
Which of the following will change the pressure in a reaction involving only gases at equilibrium? Select all that apply.
Adding an inert gas Adding or removing a reactant or product Changing the volume of the container
Match the phrases below to form sentences that correctly describe the effect of temperature changes on reactions at equilibrium.
An endothermic reaction >>> will shift to the right in response to an increase in temperature An exothermic reaction >>> will shift to the right in response to a decrease in temperature. A decrease in temperature >>> will cause an endothermic reaction to shift to the left. An increase in temperature >>> will cause an exothermic reaction to shift to the left.
Kc Kp
An equilibrium expressed in terms of the concentrations of its components An equilibrium expressed in terms of the partial pressures of its components
Which of the following options correctly describes a heterogeneous equilibrium?
An equilibrium system in which reactants and products are in different phases
A reaction is started with 2.8 M H2 (g) and 1.6 M I2 (g). Fill in the reaction table below correctly in order to calculate the value of Kc for the reaction H2 (g) + I2 (g) ⇌ 2HI (g). (Do not put any spaces between signs and numbers in your answers, and do NOT include any units or parentheses.)
Blank 1: 2x or +2x Blank 2: 2.8 - x, 2.8-x, or 2.8 -x Blank 3: 1.6-x, 1.6 - x, or 1.6 -x Blank 4: 2x, 0+2x, 0 + 2x, or +2x
The subscript "c" in the symbol Kc indicates that all components of an equilibrium expression are expressed in terms of their molar
Blank 1: concentration or concentrations
For a given reaction, Kc is the equilibrium constant based on the molar ____ of reactants and products while Kp is the quilibrium constant based on the partial ____ of reactants and products.
Blank 1: concentrations or concentration Blank 2: pressures or pressure
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.
Blank 1: decrease, lessen, or go down Blank 2: more
In a closed system a reversible chemical reaction will reach a state of dynamic chemical ____ when the rate of the forward reaction is ____ to/than the rate of the reverse reaction.
Blank 1: equilibrium Blank 2: equal or equivalent
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, and the system must produce higher ____ concentrations in order to reestablish equilibrium.
Blank 1: greater, larger, bigger, more, or higher Blank 2: reactant
An equilibrium system that contains reactants and products in different phases is called a(n) ____equilibrium system.
Blank 1: heterogeneous
A homogeneous equilibrium is established when all reacting species are in the same
Blank 1: phase, state, physical state, or state of matter
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 ____
Blank 1: position or concentrations Blank 2: the same, unchanged, same, constant, unaffected, or restored Blank 3: unchanged, the same, constant, unaffected, or not changed
To construct the expression for the equilibrium constant Kc for a given reaction, the ____ concentrations are placed in the numerator and the ____ concentrations are placed in the denominator. Each term is then raised to the power of its stoichiometric coefficient from the ____ equation.
Blank 1: product Blank 2: reactant Blank 3: balanced, molecular, or chemical
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.
Blank 1: quotient
Le Chatelier's principle states that when a chemical system at equilibrium is disturbed, the system will undergo a net reaction that _____ the effect of the disturbance and will attain a new _____ position.
Blank 1: reduces, counteracts, minimizes, offsets, decreases, lessens, counters, opposes, balances, lowers, mitigates, or buffers Blank 2: equilibrium
Which of the following statements are true about the reaction quotient, Q? Select all that apply.
Q = K only at equilibrium. Q expresses a particular ratio of products and reactants at any time during a reaction. The expression for Q is the same as the expression for K.
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.
The concentrations of the products will increase until the system reaches equilibrium again. The reaction shifts toward the products until a new equilibrium state is established.
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?
The value of K will remain unchanged because the ratio of product to reactant concentrations at equilibrium does not change.
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)
The value of KP
Which of the following statements correctly describe a chemical system at equilibrium? Select all that apply.
There is no longer a change in concentration of reactants and products over time. The forward and reverse reactions occur at equal rates.
Which of the following statements correctly reflect Le Chatelier's principle? Select all that apply.
When a system at equilibrium is disturbed, Q ≠ K. When a system at equilibrium is disturbed, the system reacts to minimize the effect of the disturbance.
The equilibrium constant Kc for a particular reaction is given by the expression [X]a[Y]b[X]a[Y]b. Match the components of this expression correctly for the balanced equation 3O2 (g) ⇌ 2O3 (g)
X - O3 a - 2 Y - O2 b - 3
At a given temperature, the values of rate constants for the forward and reverse reaction are _____ and the ratio kfkrkfkr is equal to the _____ constant for the reaction.
constant; equilibrium
increase in volume adding a gaseous reactant adding an inert gas adding a solid
decrease in pressure increase in pressure increase in total pressure, but no change in partial pressures of gases no effect on pressure
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
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
The equilibrium constant is an expression of the ratio of ______ to ______ for a system at equilibrium.
products ; reactants
When constructing an equilibrium constant expression from a given balanced equation, ______ are placed in the numerator, while ______ are placed in the denominator.
products; reactants
According to Le Chatelier's principle, when a stress is applied to a system at equilibrium, the system will ______.
react in such a way as to minimize the disturbance
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
When Q < K, the reaction will proceed so that the concentrations of the _____ decrease and the concentrations of the _____ increase.
reactants; products
The relationship between KP and Kc for an equilibrium system is given as KP = Kc(RT)Δn. The value of Δn for a given system is determined by ______.
subtracting moles of gaseous reactants from moles of gaseous products in the balanced equation
The value of KP for a given reaction is the equilibrium constant based on _____.
the partial pressures of the reactants and products
The value of K for the forward reaction is _____ the value of K for the reverse reaction.
the reciprocal of
An endothermic reaction An exothermic reaction A decrease in temperature An increase in temperature
will shift to the right in response to an increase in temperature will shift to the right in response to a decrease in temperature Will cause an endothermic reaction to shift to the left Will cause an exothermic reaction to shift to the left
Which of the following options correctly reflect the equation relating KP and Kc for a given reaction? Select all that apply. KP = Kc(RT)Δn
Δn is determined from the coefficients of the balanced equation. R = 0.0821 atm⋅L/mol⋅K T is the temperature in kelvins.
