CHEM 219 MODULE 5 PREMIUM EXAM
PREP GUIDE WITH COMPLETE
QUESTIONS AND ACCURATE ANSWERS
◉ Formula for Calculating the equilibrium constant
Answer: aA+bB → ← cC+dD
Keq = [C]^c [D]^d/[A]^a [B]^b
Keq = Theoretical Value = Products/Reactants
◉ What is reaction Quotient
Answer: Reaction Quotient = Q (experimental value) =
Products/Reactants
◉ How to know if Reaction has reached equilibrium in terms of Q
Answer: Q must equal Keq to show reaction has reached
equilibrium
◉ For the Equilibrium Constant (Keq) what does C and D
represents as well as other symbols
Answer: - C represents the equilibrium concentration of C
- D represents the equilibrium concentration of D, and so on
- Square brackets,[], are the notations for concentration in mol/L.
The power p,q,r and s represents the coefficient is equation
,◉ Characteristics of the Equilibrium Constant
Answer: - NOT include terms for substance that occur on a solid
or liquid
- NOT affected by changes in concentration or pressure
- NOT affected by the addition of a catalyst
- It is affected by changes in temperature
- It is a constant for a reaction at a given temperature
◉ When is K considered large and small K value
Answer: > 10^3 and <10^-3
◉ What does a large K value mean
Answer: Reaction favours the formation of products
Reaction will go virtually to completion
◉ What does a Small K value mean
Answer: Reaction favours the formation of reactants
Reaction will not proceed to any appreciable extent
◉ What is meant when K is between 10^3 and 10^-3
Answer: There will be significant amount of both reactants and
products present in equilibrium mixture
◉ 5 Steps in writing equilibrium constant expression
, Answer: 1. The concentrations of the reacting species in the
condensed phase are expressed in M. In the gaseous phase, the
concentrations can be expressed in M or in atm.
2. The concentrations of pure solids, pure liquids and solvents do
not appear in the equilibrium constant expressions.
3. The equilibrium constant is a dimensionless quantity.
4. In quoting a value for the equilibrium constant, you must
specify the balanced equation and the temperature.
5. If a reaction can be expressed as a sum of two or more
reactions, the equilibrium constant for the overall reaction is
given by the product of the equilibrium constants of the individual
reactions.
◉ steps To calculate for equilibrium concentrations:
Answer: 1. Express the equilibrium concentrations of all species
in terms of the initial concentrations and a single unknown x,
which represents the change in concentration.
2. Write the equilibrium constant expression in terms of the
equilibrium concentrations. Knowing the value of the equilibrium
constant, solve for x.
3. Having solved for x, calculate the equilibrium concentrations of
all species
◉ 3 factors of Reaction Quotient
Answer: - Can be calculated at any point in the reaction
- Changes depending on when its calculated
- Has the same expression as equilibrium constant
PREP GUIDE WITH COMPLETE
QUESTIONS AND ACCURATE ANSWERS
◉ Formula for Calculating the equilibrium constant
Answer: aA+bB → ← cC+dD
Keq = [C]^c [D]^d/[A]^a [B]^b
Keq = Theoretical Value = Products/Reactants
◉ What is reaction Quotient
Answer: Reaction Quotient = Q (experimental value) =
Products/Reactants
◉ How to know if Reaction has reached equilibrium in terms of Q
Answer: Q must equal Keq to show reaction has reached
equilibrium
◉ For the Equilibrium Constant (Keq) what does C and D
represents as well as other symbols
Answer: - C represents the equilibrium concentration of C
- D represents the equilibrium concentration of D, and so on
- Square brackets,[], are the notations for concentration in mol/L.
The power p,q,r and s represents the coefficient is equation
,◉ Characteristics of the Equilibrium Constant
Answer: - NOT include terms for substance that occur on a solid
or liquid
- NOT affected by changes in concentration or pressure
- NOT affected by the addition of a catalyst
- It is affected by changes in temperature
- It is a constant for a reaction at a given temperature
◉ When is K considered large and small K value
Answer: > 10^3 and <10^-3
◉ What does a large K value mean
Answer: Reaction favours the formation of products
Reaction will go virtually to completion
◉ What does a Small K value mean
Answer: Reaction favours the formation of reactants
Reaction will not proceed to any appreciable extent
◉ What is meant when K is between 10^3 and 10^-3
Answer: There will be significant amount of both reactants and
products present in equilibrium mixture
◉ 5 Steps in writing equilibrium constant expression
, Answer: 1. The concentrations of the reacting species in the
condensed phase are expressed in M. In the gaseous phase, the
concentrations can be expressed in M or in atm.
2. The concentrations of pure solids, pure liquids and solvents do
not appear in the equilibrium constant expressions.
3. The equilibrium constant is a dimensionless quantity.
4. In quoting a value for the equilibrium constant, you must
specify the balanced equation and the temperature.
5. If a reaction can be expressed as a sum of two or more
reactions, the equilibrium constant for the overall reaction is
given by the product of the equilibrium constants of the individual
reactions.
◉ steps To calculate for equilibrium concentrations:
Answer: 1. Express the equilibrium concentrations of all species
in terms of the initial concentrations and a single unknown x,
which represents the change in concentration.
2. Write the equilibrium constant expression in terms of the
equilibrium concentrations. Knowing the value of the equilibrium
constant, solve for x.
3. Having solved for x, calculate the equilibrium concentrations of
all species
◉ 3 factors of Reaction Quotient
Answer: - Can be calculated at any point in the reaction
- Changes depending on when its calculated
- Has the same expression as equilibrium constant
