Smart Book Assignment -Ch 12 - Solutions
The equilibrium constant K for a system at equilibrium expresses a particular ratio of equilibrium _______________ of products and reactants at a particular _____________.
Blank 1: concentrations, pressures, concentration, or molarities Blank 2: temperature
At a given temperature, the rate constants for the forward and reverse reaction remain _____ and the ratio kf/ kr is equal to the _____ constant for the reaction.
Blank 1: constant, the same, or unchanged Blank 2: equilibrium
An equilibrium system that contains reactants and products in different phases is called a(n) ______ equilibrium system.
heterogeneous
An equilibrium in which all reacting species are in the same phase is a(n) ______ equilibrium mixture.
homogeneous
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
Select the correct expression for the equilibrium constant for the overall reaction in a multistep process.
Koverall = K1 x K2 x K3 x...
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
tThe 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).
X= O3 , a= 2, Y=O2, b=3
Given the following reaction, which concentration terms appear in the denominator of the expression for Kc? CFCl3(g) + HCl(g) ⇌ CCl4(g) + HF(g)
[CFCl3] and [HCl]
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] and [H2]
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= 0.26
Given the balanced equation 2PbO(s) + O2(g) ⇌ 2PbO2(s), calculate the value of Δn.
-1
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 reason= Reason: Kc = (0.041) times 2(0.037)/(0.019)2
Which of the following statements correctly describe how the addition of a catalyst will affect a system at equilibrium?
1. Equilibrium is unaffected. 2. A catalyst does not change the value of K.
Which of the following statements are true about the reaction quotient, Q?
1. The expression for Q is the same as the expression for K. 2. Q = K only at equilibrium. 3. Q expresses a particular ratio of products and reactants at any time during a reaction.
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.
1. The initial [NOBr] = 0 M. 2.If the change in [Br2] = -x, then the change in [NOBr] = +2x. , 3 .x = 0.18/2 = 0.09
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.
1. The initial partial pressure of Cl2 = 0 atm. 2.If the change in partial pressure of Cl2 = +x, then at equilibrium the partial pressure of PCl3 = x. 3.Kp = 0.497 = x2/ 1.66−x
Match each of the following changes to the resulting effect on the pressure of an equilibrium system containing gaseous components. 1. increase in volume 2. adding a gaseous reactant 3. adding an inert gas 4.adding a solid
1. decrease in pressure 2. increase in pressure 3. increase in total pressure, but no change in partial pressures of gases 4.no effect on pressure
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
1. will shift to the right in response to an increase in temperature. 2. will shift to the right in response to a decrease in temperature. 3.will cause an endothermic reaction to shift to the left. 4.will cause an exothermic reaction to shift to the left.
Which of the following represent heterogeneous equilibria? Select all that apply.
1.BaCO3(s) ⇌ BaO(s) + CO2(g) 2.H2SO3(aq) ⇌ H2O(l) + SO2(g) 3.H2(g) + I2(s) ⇌ 2HI(g)
Match each of the following equations to the correct value for Δn. 1. Δn=0 2.Δn=-1 3.Δn=1
1.H2(g) + I2(g) ⇌ 2HI(g) 2.3O2(g) ⇌ 2O3(g) 3.CO2(s) ⇌ CO2(g)
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 × 10−3H2(g) + I2(g) ⇌ 2HI(g); Kc = 1.26 × 10-3 Select all the statements that correctly describe this system.
1.If the change in [H2] = +xH2 =, then at equilibrium [I2] = x 2. The initial [HI] = 0.19 M 3.Kc = 1.26 ×10^-3 = (0.19 −2x)^2/ x2
Which of the following statements correctly describe the equilibrium constant K? Select all that apply.
1.The value of K is characteristic of a particular equilibrium system. 2.K expresses a particular ratio of equilibrium concentrations of products and reactants. 3.The expression for K has the general form [products] /[reactants]
Which of the following statements correctly describe a chemical system at equilibrium? Select all that apply.
1.There is no longer a change in concentration of reactants and products over time. 2.The forward and reverse reactions occur at equal rates.
Which of the following statements correctly reflect Le Chatelier's principle?
1.When a system at equilibrium is disturbed, the system reacts to minimize the effect of the disturbance. 2.When a system at equilibrium is disturbed, Q ≠ K.
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 _______
1.position 2.same 3.unchanged
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 Reason: Kc = (2.0)(0.48)/(0.025)(9.2)= 4.2
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.)
A = 2x ,B = 2.8-x ,C = 1.6-x , D = 2x
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
Kc symbol stands for
An equilibrium expressed in terms of the concentrations of its components
Kp symbol stands for
An equilibrium expressed in terms of the partial pressures of its components
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 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
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
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 Blank 2: equilibrium
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 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
The value of K for the forward reaction is _____ the value of K for the reverse reaction.
the reciprocal of
The subscript "c" used in the symbols Qc and Kc indicate that these quantitates are based on the ______ of products and reactants.
concentrations
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
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
A homogeneous equilibrium is established when all reacting species are in the same
phase
A homogeneous equilibrium is established when all reacting species are in the same
phase, state, physical state, or state of matter (any of them will work)
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
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