Chemical Reactions and Equilibrium: Interactive Learning Quizzes

Question 1

When ice melts, which of the following statements about the process is correct?

Accepted Answer

The process is spontaneous because it results in an increase in entropy.

Answer

The process is spontaneous because it results in a decrease in entropy.

Answer

The process is not spontaneous because it is driven by an increase in enthalpy.

Answer

The process is not spontaneous because it requires the input of energy.

Question 2

Which reaction is exothermic?

Accepted Answer

Neutralizing a strong acid with a strong base

Accepted Answer

Burning methane gas

Answer

Dissolving solid ammonium chloride in water

Answer

Evaporating water

Question 3

In a chemical equilibrium, what does the equilibrium constant (Kc) represent?

Accepted Answer

The ratio of the molar concentrations of products to reactants at equilibrium

Answer

The rate at which the forward and reverse reactions occur

Answer

The change in free energy of the reaction

Answer

The temperature at which the reaction reaches equilibrium

Question 4

Which factor does NOT affect the position of equilibrium according to Le Chatelier's principle?

Accepted Answer

Catalyst presence

Answer

Temperature

Answer

Reactant concentrations

Answer

Pressure

Question 5

Which factor has no effect on the equilibrium position of a reversible reaction?

Accepted Answer

Addition of an inert gas

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Volume of the reaction vessel (for gaseous reactions)

Question 6

Which factor does NOT affect the equilibrium position of a chemical reaction?

Accepted Answer

Presence of a Catalyst

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 7

In a reversible chemical reaction, which factor has no effect on the position of equilibrium?

Accepted Answer

Addition of an inert gas

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Presence of a catalyst

Question 8

In a chemical reaction at equilibrium, which factor does NOT influence the position of equilibrium?

Accepted Answer

Solvent used in the reaction

Answer

Concentration of reactants and products

Answer

Temperature

Answer

Addition of a catalyst

Question 9

What is the key characteristic of a buffer solution?

Accepted Answer

It can neutralize small amounts of added acid or base, minimizing pH changes.

Answer

It has an extremely high or extremely low pH.

Answer

It always contains a strong acid or a strong base.

Answer

It is a good conductor of electricity.

Question 10

Which reaction involves the transfer of electrons, making it a redox reaction?

Accepted Answer

Combustion of methane in the presence of oxygen

Answer

Neutralization of an acid and a base

Answer

Precipitation of a metal hydroxide from a solution

Answer

Dissolving of ionic compounds in water

Question 11

The standard enthalpy change of formation of a compound is:

Accepted Answer

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states

Answer

The enthalpy change when 1 gram of a compound is formed from its elements in their standard states

Answer

The enthalpy change when 1 mole of a compound is decomposed into its elements in their standard states

Answer

The enthalpy change when 1 gram of a compound is decomposed into its elements in their standard states

Question 12

The equilibrium constant expression for the reaction: aA + bB <=> cC + dD is:

Accepted Answer

K = [C]^c[D]^d/[A]^a[B]^b

Answer

K = [A]^a[B]^b/[C]^c[D]^d

Answer

K = [C]^c[D]^d

Answer

K = [A]^a[B]^b

Question 13

Which of the following does NOT affect the equilibrium position of a reaction?

Accepted Answer

Presence of a catalyst

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants and products

Question 14

Le Chatelier's principle states that:

Accepted Answer

If a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress

Answer

The equilibrium constant of a reaction is constant at a given temperature

Answer

The rate of the forward reaction is equal to the rate of the reverse reaction at equilibrium

Answer

The concentration of reactants and products are equal at equilibrium

Question 15

The common ion effect is:

Accepted Answer

The addition of a common ion to a buffer solution shifts the equilibrium towards the weak acid

Answer

The addition of a common ion to a buffer solution shifts the equilibrium towards the salt

Answer

The addition of a common ion to a buffer solution has no effect on the equilibrium

Answer

The addition of a common ion to a buffer solution shifts the equilibrium towards the strong acid

Question 16

The enthalpy change for a reaction is the:

Accepted Answer

Difference in heat content between products and reactants

Answer

Heat absorbed by the surroundings

Answer

Heat released by the system

Answer

Total energy of the reaction system

Question 17

In a chemical equilibrium, the rate of the forward reaction is:

Accepted Answer

Equal to the rate of the reverse reaction

Answer

Greater than the rate of the reverse reaction

Answer

Less than the rate of the reverse reaction

Answer

Zero

Question 18

In the equilibrium:

Fe3+(aq) + 6SCN-(aq) <=> [Fe(SCN)6]3-(aq)

What happens when thiocyanate ions (SCN-) are added to the solution?

Accepted Answer

The equilibrium shifts right, forming more [Fe(SCN)6]3- ions.

Answer

The equilibrium shifts left, forming more Fe3+ ions.

Answer

The equilibrium is unaffected.

Answer

The reaction speeds up.

Question 19

The standard enthalpy change of combustion of methane is -890 kJ/mol. What is the enthalpy change when 10 moles of methane are combusted?

Accepted Answer

-8900 kJ

Answer

-8.9 kJ

Answer

-89 kJ

Answer

-890 kJ

Question 20

Which of the following reactions is exothermic?

Accepted Answer

Burning of propane

Answer

Melting of ice

Answer

Vaporisation of water

Answer

Dissolving of salt in water

Question 21

Which of the following is **not** a spontaneous process?

Accepted Answer

Melting of ice at -10°C

Answer

Evaporation of water at room temperature

Answer

Rusting of iron

Answer

Sublimation of dry ice at 0°C

Question 22

What is the conjugate acid of the base NH3?

Accepted Answer

NH4+

Answer

NH2-

Answer

H3O+

Answer

OH-

Question 23

Which of the following is the primary factor determining whether a chemical reaction is spontaneous?

Accepted Answer

Gibbs free energy change (ΔG)

Answer

Enthalpy change (ΔH)

Answer

Entropy change (ΔS)

Answer

Activation energy (Ea)

Question 24

Which of the following techniques is commonly used to measure enthalpy changes in chemical reactions?

Accepted Answer

Calorimetry

Answer

Thermometry

Answer

Gas chromatography

Answer

Mass spectrometry

Question 25

Which of the following methods is **not** commonly used to measure the pH of a solution?

Accepted Answer

UV-Vis spectrophotometer

Answer

pH paper

Answer

pH probe

Answer

Titration

Question 26

Which factors do NOT affect the equilibrium position of a chemical reaction?

Accepted Answer

Addition of an inert gas

Answer

Temperature

Answer

Concentration of reactants

Answer

Concentration of products

Question 27

A negative enthalpy change of a reaction indicates the reaction is:

Accepted Answer

Exothermic

Answer

Endothermic

Answer

Isothermal

Answer

Adiabatic

Question 28

The Gibbs free energy change of a reaction is given by:

Accepted Answer

Enthalpy change minus entropy change

Answer

Entropy change minus enthalpy change

Answer

Temperature multiplied by entropy change

Answer

Pressure multiplied by volume change

Question 29

Which of the following reactions has the largest equilibrium constant?

Accepted Answer

4aA + 4bB ⇌ 4cC + 4dD

Answer

aA + bB ⇌ cC + dD

Answer

2aA + 2bB ⇌ 2cC + 2dD

Answer

3aA + 3bB ⇌ 3cC + 3dD

Question 30

Which of the following reactions is an example of a redox reaction?

Accepted Answer

Fe + 2HCl → FeCl2 + H2

Answer

2Na + Cl2 → 2NaCl

Answer

CH4 + 2O2 → CO2 + 2H2O

Answer

NaOH + HCl → NaCl + H2O

Question 31

Consider the following reaction: A + B <=> C + D
If the concentration of A is increased, what will happen to the forward and reverse reaction rates?

Accepted Answer

Forward rate increases, reverse rate decreases

Answer

Forward rate decreases, reverse rate increases

Answer

Both rates increase

Answer

Both rates decrease

Question 32

Which of the following is a spontaneous process?

Accepted Answer

Vaporization of water at room temperature

Answer

Melting of ice at 0°C

Answer

Rusting of iron

Answer

Freezing of water at -10°C

Question 33

What is the standard entropy change for a reaction that involves the formation of a gas?

Accepted Answer

Positive

Answer

Negative

Answer

Zero

Answer

Dependent on the specific gas

Question 34

What is the free energy change for a reaction when it has reached equilibrium?

Accepted Answer

0

Answer

Negative

Answer

Indeterminate

Answer

Positive

Question 35

What is the equilibrium constant for a reaction under standard conditions?

Accepted Answer

1

Answer

Less than 1

Answer

Greater than 1

Answer

0

Question 36

Define the activation energy of a reaction.

Accepted Answer

The minimum energy required for a reaction to occur

Answer

The maximum energy released by a reaction

Answer

The difference in energy between the reactants and products

Question 37

Which of the following correctly defines enthalpy change for a reaction?

Accepted Answer

The heat transferred to or from the surroundings at constant pressure

Answer

The change in internal energy of the system

Answer

The heat transferred to or from the surroundings at constant volume

Question 38

Entropy change for a reaction is defined as:

Accepted Answer

The change in the disorder or randomness of the system

Answer

The change in the internal energy of the system

Answer

The change in the free energy of the system

Question 39

Free energy change for a reaction is:

Accepted Answer

The maximum amount of work that can be done by the system at constant temperature and pressure

Answer

The heat transferred to or from the surroundings at constant pressure

Answer

The change in internal energy of the system at constant temperature and pressure

Question 40

Which is a characteristic of a system at equilibrium?

Accepted Answer

The concentrations of reactants and products do not change over time

Answer

The system is constantly changing

Answer

The system is exothermic

Question 41

A reaction with a negative enthalpy change and a positive entropy change is:

Accepted Answer

Spontaneous at high temperatures

Answer

Non-spontaneous at high temperatures

Answer

Non-spontaneous at all temperatures

Answer

Spontaneous at all temperatures

Question 42

If the equilibrium constant for a reaction is less than 1, then the reaction:

Accepted Answer

Favours the reactants

Answer

Favours the products

Answer

Is at equilibrium

Answer

Has no net change

Question 43

Which of the following processes is non-spontaneous?

Accepted Answer

Charging a battery

Answer

Melting ice at room temperature

Answer

Dissolving sugar in water

Question 44

Entropy is a measure of:

Accepted Answer

The randomness or disorder of a system

Answer

The potential energy of a system

Answer

The kinetic energy of a system

Answer

The heat content of a system

Question 45

A reaction with a positive free energy change is:

Accepted Answer

Non-spontaneous

Answer

Reversible

Answer

At equilibrium

Answer

Spontaneous

Question 46

What is the enthalpy change of a reaction?

Accepted Answer

The heat absorbed or released by a reaction at constant pressure.

Answer

The total energy content of the products.

Answer

The difference in energy between reactants and products at constant volume.

Answer

The energy required to break the bonds in the reactants.

Question 47

A reaction has a negative enthalpy change (ΔH) and a positive entropy change (ΔS). What can be concluded about the spontaneity of the reaction?

Accepted Answer

The reaction is spontaneous at all temperatures.

Answer

The reaction is spontaneous at high temperatures only.

Answer

The reaction is spontaneous at low temperatures only.

Answer

The reaction is non-spontaneous at all temperatures.

Question 48

A closed system contains reactants A and B in equilibrium with products C and D. What happens if more of reactant A is added to the system?

Accepted Answer

The equilibrium shifts to the right, favoring the formation of products.

Answer

The equilibrium shifts to the left, favoring the formation of reactants.

Answer

The equilibrium position remains unchanged.

Answer

The equilibrium constant (Kc) increases.

Question 49

Which of the following factors directly affects the value of the equilibrium constant (Kc)?

Accepted Answer

Temperature

Answer

Pressure

Answer

Addition of a catalyst

Answer

Concentration of reactants

Question 50

The following reaction is at equilibrium: N2(g) + 3H2(g) ⇌ 2NH3(g). What happens to the equilibrium position if the pressure is increased?

Accepted Answer

The equilibrium shifts to the right, favoring the formation of ammonia.

Answer

The equilibrium position does not change.

Answer

The equilibrium shifts to the left, favoring the formation of nitrogen and hydrogen.

Answer

The equilibrium constant (Kc) decreases.

Question 51

A reaction has a ΔH° of +50 kJ/mol and a ΔS° of +100 J/mol K. At what temperature will the reaction become spontaneous?

Accepted Answer

Above 500 K

Answer

At no temperature

Answer

Below 500 K

Answer

At all temperatures

Question 52

What is the standard enthalpy change of formation (ΔHf°) of a compound?

Accepted Answer

The enthalpy change when one mole of the compound is formed from its elements in their standard states.

Answer

The enthalpy change when one mole of the compound is decomposed into its elements.

Answer

The enthalpy change of a reaction at standard conditions.

Question 53

The Haber process is used to manufacture ammonia from nitrogen and hydrogen gases. What is the main purpose of using a catalyst in this process?

Accepted Answer

To increase the rate of reaction without affecting the equilibrium position.

Answer

To shift the equilibrium position to favor the formation of ammonia.

Answer

To decrease the activation energy of the reverse reaction.

Answer

To increase the yield of ammonia.

Question 54

The free energy change (ΔG) of a reaction is negative. What does this indicate about the reaction?

Accepted Answer

The reaction is spontaneous and will proceed without an input of energy.

Answer

The reaction is in equilibrium.

Answer

The reaction is non-spontaneous and requires an input of energy to proceed.

Answer

The reaction is exothermic.

Question 55

What is the equilibrium constant expression, Kc, for the following reversible reaction: A + B ⇌ C + D?

Accepted Answer

Kc = [C][D] / [A][B]

Answer

Kc = [A][B] / [C][D]

Answer

Kc = [C] / [A]

Answer

Kc = [D] / [B]

Question 56

Which of the following solutions would act as a buffer?

Accepted Answer

A mixture of a weak acid and its conjugate base

Answer

A solution of a salt

Answer

A solution of a strong base

Answer

A solution of a strong acid

Question 57

What is the standard enthalpy change of combustion (ΔH°c) for methane (CH4) in kJ/mol?

Accepted Answer

-890 kJ/mol

Answer

890 kJ/mol

Answer

-286 kJ/mol

Answer

1780 kJ/mol

Question 58

What is the activation energy (Ea) of a chemical reaction?

Accepted Answer

The minimum amount of energy that reactant molecules must possess to initiate a reaction

Answer

The energy released during the reaction

Answer

The energy difference between reactants and products

Answer

The maximum amount of energy that reactants can possess

Question 59

The standard enthalpy change of combustion of methane is -890 kJ/mol. What is the enthalpy change when 2 moles of methane are completely combusted?

Accepted Answer

-1780 kJ

Answer

890 kJ

Answer

-890 kJ

Answer

1780 kJ

Question 60

A reaction reaches equilibrium when:

Accepted Answer

The rates of the forward and reverse reactions become equal.

Answer

The concentrations of reactants and products are equal.

Answer

The reaction has stopped completely.

Question 61

Which of the following processes is an example of an exothermic reaction?

Accepted Answer

The combustion of fuels, like wood or propane

Answer

The dissolving of ammonium nitrate in water (an endothermic process)

Answer

The melting of ice

Answer

The evaporation of water

Question 62

The equilibrium constant, Kc, for a certain reaction is 10^4. What does this indicate about the position of equilibrium?

Accepted Answer

The products are strongly favored at equilibrium.

Answer

The reaction is very fast.

Answer

The reactants are strongly favored at equilibrium.

Answer

The reaction is very slow.

Question 63

Which of the following statements correctly describes the effect of a catalyst on a reaction at equilibrium?

Accepted Answer

A catalyst speeds up both the forward and reverse reactions equally, so the equilibrium position remains unchanged.

Answer

A catalyst shifts the equilibrium position towards the products.

Question 64

A reaction has a ΔH value of +50 kJ/mol and a ΔS value of +100 J/mol K. At what temperature will the reaction become spontaneous?

Accepted Answer

Above 500 K

Answer

Below 500 K

Answer

At all temperatures