Question 1

Given a K of 0.45 at 25°C, calculate the corresponding DG°in kJ/mol. [R = 8.314 J/K∙ mol]

Accepted Answer

The answer of Given a K of 0.45 at 25°C,...

Question 2

Which is a measure of the randomness of a system?

Accepted Answer

Entropy is a measure of the randomness or disorder of a system. It increases with an increase in the number of microstates available to a system, which corresponds to an increase in disorder. The other options listed are not related to randomness or disorder of a system.

Question 3

Given a K of 2.2 at 25°C, calculate the corresponding DG°in kJ/mol. [R = 8.314 J/K∙ mol]

Accepted Answer

The answer of Given a K of 2.2 at 25°C,...

Question 4

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is +0.5 kcal/mol, the K_eq is ________ and the % conversion is ________.

Accepted Answer

The answer of Consider the reaction of A being converted...

Question 5

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is the K_eq is ________ and the % conversion is ________.

Accepted Answer

The answer of Consider the reaction of A being converted...

Question 6

If the equilibrium constant (K_eq) of a reaction is 0.5 then which of the following that must be true?

Accepted Answer

If the equilibrium constant (K) of a reaction is less than 1 (K < 1), it means that the reaction favors the reactants over the products at equilibrium. This implies that the Gibbs free energy change (ΔG) for the reaction is positive, indicating that the reaction is not spontaneous in the forward direction under standard conditions.

Question 7

For the reaction A + B → C + D, ΔG° = -5.00 kcal/mol. What is the corresponding equilibrium constant at 25°C? R = 1.987 cal/mol∙K.

Accepted Answer

The answer of For the reaction A + B →...

Question 8

Which of the following is true for the initiation step of a free radical chlorination reaction?

Accepted Answer

The initiation step of a free radical chlorination reaction involves breaking the chlorine-chlorine bond using UV light or heat, which requires energy and results in an increase in entropy due to the formation of two chlorine radicals. Therefore, ΔH° and ΔS° both have positive values, making choice A the correct answer.

Question 9

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is -0.5 kcal/mol, the K_eq is ________ and the % conversion is ________.

Accepted Answer

The answer of Consider the reaction of A being converted...

Question 10

Provided the following pK_a values for the two acids below, draw an energy diagram for the acid-base reaction. Be sure to label each axis correctly.

Accepted Answer

The answer of Provided the following pK_a values for the...

Question 11

If a reaction is exothermic, then:

Accepted Answer

Exothermic reactions release heat, which means that the enthalpy change (ΔH°) is negative. Therefore, the correct choice is C. The sign of the entropy change (ΔS°) cannot be determined solely based on whether a reaction is exothermic or endothermic.

Question 12

Consider the transformation of A to B (i.e., A →
B). If at equilibrium at 25°C the concentration of A is 20% of the initial concentration of A, determine the value of ΔG° (in kcal/mol) for this reaction.
R = 1.987 cal/mol∙K.

Accepted Answer

The answer of Consider the transformation of A to B...

Question 13

Which of the following correctly expresses the standard Gibbs free energy change of a reaction in terms of the changes in enthalpy and entropy?

Accepted Answer

This statement is known as the Gibbs-Helmholtz equation and expresses the standard Gibbs free energy change (ΔG°) in terms of the standard enthalpy change (ΔH°) and the standard entropy change (ΔS°) at a constant temperature (T). The minus sign indicates that the reaction is spontaneous (favorable) when ΔG° is negative.

Question 14

Given a DG°of 0.8 kJ/mol at 25°C for the equilibrium shown below, calculate the percentage of the axial conformer at 25°C. [R = 8.314 J/K∙ mol]

Accepted Answer

The answer of Given a DG°of 0.8 kJ/mol at...

Question 15

Given a reaction in which reactant A is converted only to product B at 25°C, what K_eq results if at equilibrium 80% of A has become B?

Accepted Answer

The answer of Given a reaction in which reactant A...

Question 16

Which of the following statements correctly describes the contribution of ΔS° to ΔG°?

Accepted Answer

The contribution of ΔS° to ΔG° is given by the equation ΔG° = ΔH° - TΔS°, where T is the temperature in Kelvin. At high temperatures, the TΔS° term becomes more significant and can even override the ΔH° term. Therefore, B is the correct choice.

Question 17

In an exothermic reaction, are stronger bonds broken and weaker bonds formed or are weaker bonds broken and stronger bonds formed?

Accepted Answer

The answer of In an exothermic reaction, are stronger bonds...

Question 18

Consider the following substitution reaction with a ΔG° value of -91.1 kJ/mole. HO- + CH₃Cl ↔ CH₃OH + Cl- Given this information which of the following statements must be true? (R = 8.315 J/mole K)

Accepted Answer

A negative ΔG° indicates that the reaction is spontaneous and proceeds in the forward direction under standard conditions. Additionally, a negative ΔG° means that the reaction is exergonic and releases energy. The magnitude of the ΔG° indicates the extent to which the reaction will go towards completion. Therefore, a large negative ΔG° value (-91.1 kJ/mole in this case) suggests that the equilibrium will be heavily shifted towards the products (CH₃OH and Cl-) and the reaction will proceed nearly to completion (left to right) under standard conditions. The equilibrium constant (Keq) is related to ΔG° by the equation ΔG°=-RTln(Keq). Using this equation, we can calculate the equilibrium constant at 25°C as Keq=e^(-ΔG°/RT), which comes out to be very large (>>1), supporting our conclusion that the reaction proceeds nearly to completion in the forward direction under standard conditions. Option A is therefore the correct answer. Option B is ruled out because a negative ΔG° value implies that the reaction favors the forward direction. Option C is incorrect because a change in temperature will affect the equilibrium constant, but the question does not provide any information to support a conclusion that the equilibrium is shifted towards the products at 250°C. Option D is also incorrect because a large negative ΔG° value suggests that there is a significant difference in the concentrations of the products and reactants at equilibrium under standard conditions. Option E is not correct because Option C is not a valid choice.

Question 19

Given a DG°of -8.0 kJ/mol at 25°C, calculate the corresponding K. [R = 8.314 J/K∙ mol]

Accepted Answer

The answer of Given a DG°of -8.0 kJ/mol at...

Question 20

Assume the reaction A + B → C + D proceeds to equilibrium. Calculate the equilibrium concentration of D at 25°C, given that the starting concentrations of A and B are 2M and that ΔG° for the reaction is 1.0 kcal/mol. R = 1.987 cal/mol∙K.

Accepted Answer

The answer of Assume the reaction A + B →...

Quiz 4: The Study of Chemical Reactions

Given a K of 0.45 at 25°C, calculate the corresponding DG°in kJ/mol. [R = 8.314 J/K∙ mol]

Which is a measure of the randomness of a system?

Given a K of 2.2 at 25°C, calculate the corresponding DG°in kJ/mol. [R = 8.314 J/K∙ mol]

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is +0.5 kcal/mol, the K_eq is and the % conversion is .

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is the K_eq is and the % conversion is .

If the equilibrium constant (K_eq) of a reaction is 0.5 then which of the following that must be true?

For the reaction A + B → C + D, ΔG° = -5.00 kcal/mol. What is the corresponding equilibrium constant at 25°C? R = 1.987 cal/mol∙K.

Which of the following is true for the initiation step of a free radical chlorination reaction?

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is -0.5 kcal/mol, the K_eq is and the % conversion is .

Provided the following pK_a values for the two acids below, draw an energy diagram for the acid-base reaction. Be sure to label each axis correctly.

If a reaction is exothermic, then:

Consider the transformation of A to B (i.e., A → B). If at equilibrium at 25°C the concentration of A is 20% of the initial concentration of A, determine the value of ΔG° (in kcal/mol) for this reaction. R = 1.987 cal/mol∙K.

Which of the following correctly expresses the standard Gibbs free energy change of a reaction in terms of the changes in enthalpy and entropy?

Given a DG°of 0.8 kJ/mol at 25°C for the equilibrium shown below, calculate the percentage of the axial conformer at 25°C. [R = 8.314 J/K∙ mol]

Given a reaction in which reactant A is converted only to product B at 25°C, what K_eq results if at equilibrium 80% of A has become B?

Which of the following statements correctly describes the contribution of ΔS° to ΔG°?

In an exothermic reaction, are stronger bonds broken and weaker bonds formed or are weaker bonds broken and stronger bonds formed?

Consider the following substitution reaction with a ΔG° value of -91.1 kJ/mole. HO- + CH₃Cl ↔ CH₃OH + Cl- Given this information which of the following statements must be true? (R = 8.315 J/mole K)

Given a DG°of -8.0 kJ/mol at 25°C, calculate the corresponding K. [R = 8.314 J/K∙ mol]

Assume the reaction A + B → C + D proceeds to equilibrium. Calculate the equilibrium concentration of D at 25°C, given that the starting concentrations of A and B are 2M and that ΔG° for the reaction is 1.0 kcal/mol. R = 1.987 cal/mol∙K.

Quiz 4: The Study of Chemical Reactions

Given a K of 0.45 at 25°C, calculate the corresponding DG° in kJ/mol. [R = 8.314 J/K∙ mol]

Which is a measure of the randomness of a system?

Given a K of 2.2 at 25°C, calculate the corresponding DG° in kJ/mol. [R = 8.314 J/K∙ mol]

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is +0.5 kcal/mol, the Keq is ________ and the % conversion is ________.

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is the Keq is ________ and the % conversion is ________.

If the equilibrium constant (Keq) of a reaction is 0.5 then which of the following that must be true?

For the reaction A + B → C + D, ΔG° = -5.00 kcal/mol. What is the corresponding equilibrium constant at 25°C? R = 1.987 cal/mol∙K.

Which of the following is true for the initiation step of a free radical chlorination reaction?

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is -0.5 kcal/mol, the Keq is ________ and the % conversion is ________.

Provided the following pKa values for the two acids below, draw an energy diagram for the acid-base reaction. Be sure to label each axis correctly.

If a reaction is exothermic, then:

Consider the transformation of A to B (i.e., A → B). If at equilibrium at 25°C the concentration of A is 20% of the initial concentration of A, determine the value of ΔG° (in kcal/mol) for this reaction. R = 1.987 cal/mol∙K.

Which of the following correctly expresses the standard Gibbs free energy change of a reaction in terms of the changes in enthalpy and entropy?

Given a DG° of 0.8 kJ/mol at 25°C for the equilibrium shown below, calculate the percentage of the axial conformer at 25°C. [R = 8.314 J/K∙ mol]

Given a reaction in which reactant A is converted only to product B at 25°C, what Keq results if at equilibrium 80% of A has become B?

Which of the following statements correctly describes the contribution of ΔS° to ΔG°?

In an exothermic reaction, are stronger bonds broken and weaker bonds formed or are weaker bonds broken and stronger bonds formed?

Consider the following substitution reaction with a ΔG° value of -91.1 kJ/mole. HO- + CH3Cl ↔ CH3OH + Cl- Given this information which of the following statements must be true? (R = 8.315 J/mole K)

Given a DG° of -8.0 kJ/mol at 25°C, calculate the corresponding K. [R = 8.314 J/K∙ mol]

Assume the reaction A + B → C + D proceeds to equilibrium. Calculate the equilibrium concentration of D at 25°C, given that the starting concentrations of A and B are 2M and that ΔG° for the reaction is 1.0 kcal/mol. R = 1.987 cal/mol∙K.

Given a K of 0.45 at 25°C, calculate the corresponding DG°in kJ/mol. [R = 8.314 J/K∙ mol]

Given a K of 2.2 at 25°C, calculate the corresponding DG°in kJ/mol. [R = 8.314 J/K∙ mol]

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is +0.5 kcal/mol, the K_eq is and the % conversion is .

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is the K_eq is and the % conversion is .

If the equilibrium constant (K_eq) of a reaction is 0.5 then which of the following that must be true?

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is -0.5 kcal/mol, the K_eq is and the % conversion is .

Provided the following pK_a values for the two acids below, draw an energy diagram for the acid-base reaction. Be sure to label each axis correctly.

Given a DG°of 0.8 kJ/mol at 25°C for the equilibrium shown below, calculate the percentage of the axial conformer at 25°C. [R = 8.314 J/K∙ mol]

Given a reaction in which reactant A is converted only to product B at 25°C, what K_eq results if at equilibrium 80% of A has become B?

Consider the following substitution reaction with a ΔG° value of -91.1 kJ/mole. HO- + CH₃Cl ↔ CH₃OH + Cl- Given this information which of the following statements must be true? (R = 8.315 J/mole K)

Given a DG°of -8.0 kJ/mol at 25°C, calculate the corresponding K. [R = 8.314 J/K∙ mol]