Unit 5 - Chemical Equilibrium Flashcards
T/F
Most chemical reactions are irreversible. Only few reactions proceed to completion.
F
It exists when two opposing reactions occur simultaneously at the same rate.
Chemical equlibrium
It is a dynamic process.
Chemical equilibrium
T/F
Once equilibrium is achieved, the amount of each reactant and product remains constant.
T
T/F
As a system approaches equilibrium, both the forward and reverse reactions are occuring.
T
All reactants and products are in same phase and cannot be separated.
Homogenous equilibrium
Reactants and products are not in homogenous phase and can be separated.
Heterogenous equilibrium
T/F
The forward rate will be the reactant side.
T
T/F
The reverse rate will be the product side.
T
States that the rate of any chemical reaction is proportional to the product of the masses of the reacting substances, with each mass raised to a power equal to the coefficient that occurs in the chemical equation.
Law of mass action
It relates the concentrations of reactants and products at equilibrium.
Equilibrium constant
T/F
It is the product of the concentrations of PRODUCTS of a chemical equilibrium divided by the concentrations of REACTANTS, each raised to the power equal to its coefficient in the balanced chemical equation.
T
T/F
In writing equilibrium constant expression, a pure solid or a pure liquid in the reaction is omitted from the expression.
T
T/F
The concentration of a pure solid or a pure liquid is always the same.
T
The activity of liquid or solid is defined as _____.
1
T/F
H2O(l) has activity of 1 while H2O(g) is considered in the expression.
T
This results from a reversible reaction involving reactants and products that are in different phases.
Heterogeneous equilibrium
T/F
In heterogeneous equilibrium, neither density nor molar mass is a variable, the concentrations of solids and pure liquids are constant.
T
T/F
The concentrations of pure liquids and pure solids are not included in equilibrium constant expressions.
T
The larger K the more _____ are present at equilibrium.
A. Reactants
B. Products
B
The smaller K the more _____ are present at equilibrium.
A. Reactants
B. Products
A
If K > 1, then products dominate at equilibrium and equilibrium lies to the _____.
A. Left
B. Right
B
If K < 1, then products dominate at equilibrium and equilibrium lies to the _____.
A. Left
B. Right
A
If K > 1, the reaction is _____.
A. Product-favored; product predominates at equilibrium.
B. Reactant-favored; reactant predominates at equilibrium
A
If K < 1, the reaction is _____.
A. Product-favored; product predominates at equilibrium.
B. Reactant-favored; reactant predominates at equilibrium
B
T/F
In the magnitude of equilibrium constants, an equilibrium can be approached from any direction.
T
The ___ for a reaction in one direction is the reciprocal of the equilibrium constant of the reaction in the opposite direction.
Kc
It is the equilibrium constant for a net reaction made up of two or more steps is the product of the equilibrium constants for the individual steps.
Multiple equilibria
T/F
In predicting the direction of the reaction, the reaction quotient, Q, for a reaction at conditions NOT at equilibrium.
T
T/F
Q = K only at equilibrium.
T
If K = Q the _____.
A. System is at equilibrium.
B. Forward reaction is favored.
C. Reverse reaction is favored.
A
If K > Q the _____.
A. System is at equilibrium.
B. Forward reaction is favored.
C. Reverse reaction is favored.
B
If K < Q the _____.
A. System is at equilibrium.
B. Forward reaction is favored.
C. Reverse reaction is favored.
C
T/F
Changes in experimental conditions may disturb the balance and shift the equilibrium.
T
Factors that affect equilibrium.
Concentration
Catalyst
Temperature
Volume and Pressure
A principle wherein if stress is applied to a system that is in equilibrium, the system will adjust in such a way that the stress is partially offset as the system reaches a new equilibrium position.
Le Chatelier’s Principle
A + B ⇋ C + D
Increasing the amount of A or B.
A. Forward
B. Reverse
C. No shift
A
A + B ⇋ C + D
Increasing the amount of C or D.
A. Forward
B. Reverse
C. No shift
B
A + B ⇋ C + D
Decreasing the amount of A or B.
A. Forward
B. Reverse
C. No shift
B
A + B ⇋ C + D
Decreasing the amount of C or D.
A. Forward
B. Reverse
C. No shift
A
A + B ⇋ C + D
Reacting A with compound E.
A. Forward
B. Reverse
C. No shift
B
A + B ⇋ C + D
Removing C as the reaction proceeds.
A. Forward
B. Reverse
C. No shift
A
A system that RELEASES heat to the surroundings, has a negative ΔH (-ΔH) by convention, because the enthalpy of the products is LOWER than the enthalpy of the reactants of the system.
Exothermic reaction
A system of reactants that ABSORBS heat from the surroundings in a reaction has a positive ΔH (+ ΔH), because the HIGHER of the products is HIGHER than the enthalpy of the reactants of the system.
Endothermic reaction
Changes in volume and pressure affect only systems involving _____.
A. Solid
B. Liquid
C. Gases
C
T/F
Changes in volume and pressure increase in pressure or decrease in volume favors the reaction where there is less total number of moles of gases.
T
T/F
Changes in volume and pressure decrease in pressure or increase in volume favors the reaction where there is higher total number of moles of gases.
T
T/F
Presence of catalyst does not affect the state of equilibrium.
T
T/F
Presence of catalyst allows the system to reach equilibrium faster.
T
