Unit 6 Lesson 3 Chem
An equilibrium calculation can be simplified by taking square roots on both sides of the equation when _____.
both numerator and denominator in the expression for K are perfect squares
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.
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
If O2(g) is added to the equilibrium system 2NO(g) ⇌ N2(g) + O2(g), which of the following will be observed? Select all that apply.
The concentration of NO will increase. The reaction will shift to the left.
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)20.39(2.0-0.78)2 = 0.26
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 is ; B is C is ; D is
2x; 2.8-x; 1.6-x; 2x
Which equilibrium below will shift to the right in response to an increase in temperature?
3O2(g) ⇌ 2O3(g) ΔH = +284.6 kJ
Which of the following changes will cause the equilibrium shown to shift toward the products? Select all that apply. Fe3O4(s) + 4H2(g) ⇌ 3Fe(s) + 4H2O(g)
Add H2(g) without changing the volume. Remove H2O(g) from the reaction vessel.
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 Changing the volume of the container Adding or removing a reactant or product
0.45 mol PCl5(g) is placed in a sealed 2.0-L container and reacts according to the equation PCl5(g) ⇌ PCl3(g) + Cl2(g). If [Cl2] = 0.10 M at equilibrium, select all the options that correctly reflect the steps required to calculate Kc.
At equilibrium [PCl3] = 0.10 M. The initial [PCl5] = 0.23 M. Kc = (0.10)(0.10)(0.13)
Which of the following correctly reflect ways in which a chemical equilibrium can be disturbed? Select all that apply.
Changing the temperature of the system Changing the concentrations of reactants or products Changing the volume of the reaction container for a reaction involving gases
Consider the equilibrium system C2H4(g) + H2O(g) ⇌ C2H5OH(g); ΔHo = -47.8 kJ. What will be observed if the temperature of the system is increased?
Equilibrium will shift toward the reactants. Kc will decrease.
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. The initial [NOBr] = 0 M. x = 0.1820.182 = 0.09
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 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 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 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
Match the effect of each change described to the correct description of the resulting shift in equilibrium. Assume the system is at equilibrium before any change is made, and that all changes occur at constant temperature. SO2(g) + Cl2(g) ⇌ SO2Cl2(g)
Increase the volume of the container - Equilibrium shifts toward the reactants. Double the partial pressures of all species - Equilibrium shifts toward the products. Add 1 mol of Ne (g) - Equilibrium will be unaffected.
Which of the following equilibrium calculations can be simplified by taking square roots on both sides of the equation? Select all that apply.
K = 0.15 = x2(0.1−x)(0.1−x)x2(0.1-x)(0.1-x) K = 420 = (0.1+x)(0.1+x)(2x)2
A flask is charged with 0.50 atm of H2 (g) and 0.50 atm of I2 (g) at 450°C and reacts according to the equation H2(g) + I2(g) ⇌ 2HI(g). If the partial pressure of H2 at equilibrium = 0.11 atm, which of the following gives the correct calculation for Kp?
KP = (0.78)2(0.11)2(0.78)2(0.11)2 = 50.
Which of the following reactions will not undergo a shift in equilibrium position when the volume or pressure changes? Select all that apply. Assume that each system is at equilibrium before changes occur, and that the temperature remains constant throughout.
N2(g) + O2(g) ⇌ 2NO(g) H2(g) + Cl2(g) ⇌ 2HCl(g)
Consider the addition or removal of Substance A from the equilibrium shown. Match each action with the reaction the system will undergo in order to reestablish equilibrium. A + B ⇌ C + D
Substance A is added to the system. - The system will react by consuming Substance A in order to reestablish equilibrium. Substance A is removed from the system - The system will react by producing more of Substance A in order to reestablish equilibrium.
Which of the following statements correctly explain why the addition of an inert gas to an equilibrium system involving gases does not cause a shift in the equilibrium position? Select all that apply.
The concentrations and the partial pressures of the gases involved in the reaction remain unchanged. The inert gas is not included in the expression for Q.
For the following reaction, what will be observed if the volume is increased at constant temperature? Select all that apply. 2NO2(g) ⇌ 2NO(g) + O2(g)
The concentrations of all species will decrease at the instant the volume is changed. The equilibrium position will shift toward the products.
Consider the equilibrium system C(s) + H2O(g) ⇌ CO(g) + H2(g); ΔHo = 131 kJ. What will be observed if the temperature of the system is decreased? Select all that apply.
The equilibrium concentration of H2O (g) will increase. The value of Kc will decrease. Equilibrium will shift toward the reactants.
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.
The initial [N2] = 0 M. If the change in [N2] = +x, then the change in [NO] = -2x. x = 0.10−0.06220.10-0.0622 = 0.019
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.
The initial partial pressure of Cl2 = 0 atm. If the change in partial pressure of Cl2 = +x, then at equilibrium the partial pressure of PCl3 = x. Kp = 0.497 = x21.66−x
In a given experiment, 0.10 atm of each component in the following reaction is placed in a sealed container. In which direction will the reaction proceed? 2NOBr(g) ⇌ 2NO(g) + Br2(g) where KP = 60.6 at 100°C
The reaction proceeds toward the products.
In a given experiment, 0.10 atm of each component in the following reaction is placed in a sealed container. In which direction will the reaction proceed? 2NOBr(g) ⇌ 2NO(g) + Br2(g) where KP = 60.6 at 100°C Multiple choice question.
The reaction proceeds toward the products.
Q < K Q = K Q > K
The reaction proceeds toward the products. The system is at equilibrium and no further net change occurs. The reaction proceeds toward the reactants
In a given experiment, 0.45 atm of each component in the following reaction is placed in a sealed container. In which direction will the reaction proceed? 2SO3(g) ⇌ 2SO2(g) + O2(g) where KP = 0.338 at 1000 K
The reaction proceeds toward the reactants.
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. The concentrations of the products will increase until the system reaches equilibrium again.
Substance C is added to the system. Substance C is removed from the system.
The system will shift to the left. The system will shift to the right.
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
When Q > K, the amount of the products must _____ and the amount of the reactants must _____ until equilibrium is established. The reaction will proceed toward the _____.
decrease; increase; reactants
If a system at equilibrium is disturbed by a change in concentration, the system will shift to _____ a substance that is added and to _____ a substance that has been removed.
consume; produce
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
Match each of the following changes to the resulting effect on the pressure of an equilibrium system containing gaseous components.
increase in volume - decrease in pressure adding a gaseous reactant - increase in total pressure, but no change in partial pressures of gases adding an inert gas - increase in pressure adding a solid - no effect on pressure
As a reaction proceeds, the value of Q _____.
increases or decreases, as necessary, until it reaches the value of K
Three common ways of disturbing a system at equilibrium are to change the concentrations of reactants and/or products, the temperature, or the of the system.
pressure
The equilibrium constant expression for a particular reaction is given by Kc = (2x)2(0.1−x)(0.2−2x)(2x)2(0.1-x)(0.2-2x). In this case, the formula must be used to solve for x.
quadratic
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 _____. Multiple choice question.
reactants; products
When Q < K, the reaction will proceed so that the concentrations of the _____ decrease and the concentrations of the _____ increase. Multiple choice question.
reactants; products
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.
reduces; equilibrium
The reaction quotient Q expresses a ratio of product concentrations to reactant concentrations at any point in a reaction. Q is only equal to K when ______.
the reaction has reached equilibrium
True or false: If the reaction shown below is at equilibrium, that equilibrium will be stressed by decreasing the volume of the reaction vessel. 2NO(g) + O2(g) ⇌ 2NO2(g)
true
