Which factors must be equal in a reversible chemical reaction at equilibrium?

the rates of reaction of the foward and reverse reactions

the concentrations of the reactants and products

the potential energies of the reactants and products

the activation energies of the foward and reverse reactions

the rates of reaction of the foward and reverse reactions

In a reversible reaction, chemical equilibrium is attained when the

concentration of the products remains constant

rate of the foward reaction is greater than the rate of the reverse reaction

rate of the reverse reaction in greater than the rate of the forward reaction

concentration of the reactants reaches zero

concentration of the products remains constant

The equilibrium constant for a given system will change when:

the reactant concentration changes

When is equilibrium reached in a chemical reaction?

The rates of the forward and reverse reactions become equal.

When the forward reaction stops.

The concentrations of the reactants and products become equal.

The rates of the forward and reverse reactions become equal.

For a system at equilibrium, lowering the temperature will always:

increase the rate of the reaction

increase the concentrations of the products

Which change may occur in a reaction system when a catalyst is addded?

The point of equilibrium is reached more rapidly.

The potential energy of the reactants increases.

The potential energy of the products increases.

The point of equilibrium is reached more rapidly.

The heat of reaction decreased.

Equilibrium Chemical Reaction Quiz Questions

1.

Which factors must be equal in a reversible chemical reaction at equilibrium?
- A.
  
  The concentrations of the reactants and products
- B.
  
  The potential energies of the reactants and products
- C.
  
  The activation energies of the foward and reverse reactions
- D.
  
  The rates of reaction of the foward and reverse reactions
Correct Answer
D. The rates of reaction of the foward and reverse reactions

Explanation
In a reversible chemical reaction at equilibrium, the rates of the forward and reverse reactions must be equal. This means that the rate at which reactants are being converted into products is the same as the rate at which products are being converted back into reactants. This balance between the rates of the forward and reverse reactions ensures that the concentrations of the reactants and products remain constant, leading to a stable equilibrium state. The concentrations of the reactants and products, potential energies, and activation energies may vary, but it is the rates of reaction that must be equal for equilibrium.

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2.

In a reversible reaction, chemical equilibrium is attained when the
- A.
  
  Rate of the foward reaction is greater than the rate of the reverse reaction
- B.
  
  Rate of the reverse reaction in greater than the rate of the forward reaction
- C.
  
  Concentration of the reactants reaches zero
- D.
  
  Concentration of the products remains constant
Correct Answer
D. Concentration of the products remains constant

Explanation
In a reversible reaction, chemical equilibrium is attained when the concentration of the products remains constant. This means that the rate of the forward reaction is equal to the rate of the reverse reaction, resulting in no net change in the concentration of the products over time. At equilibrium, the reactants are still being converted into products, but at the same rate that products are being converted back into reactants. This dynamic balance between the forward and reverse reactions is what defines chemical equilibrium.

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3.

Given the reaction at equilibrium:A(g) + B(g) + heat<----> AB(g)As the pressure increases at constant temperature, the value of the equilibrium constant
- A.
  
  Decreases
- B.
  
  Increases
- C.
  
  Remains the same
Correct Answer
C. Remains the same

Explanation
The value of the equilibrium constant remains the same when the pressure increases at constant temperature because the equilibrium constant is determined by the ratio of the concentrations of the reactants and products, not the pressure. Increasing the pressure will cause the system to shift towards the side with fewer moles of gas in order to decrease the pressure, but this does not affect the equilibrium constant. Therefore, the value of the equilibrium constant remains unchanged.

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4.

Which type of reaction is most favored by an increase in temperature?
- A.
  
  Endothermic
- B.
  
  Exothermic
- C.
  
  Spontaneous
Correct Answer
A. Endothermic

Explanation
An increase in temperature favors endothermic reactions because these reactions absorb heat from the surroundings. When the temperature rises, more heat is available for the reaction to absorb, which increases the reaction rate. This is because endothermic reactions require an input of energy to proceed, and higher temperatures provide the necessary energy. In contrast, exothermic reactions release heat, so increasing the temperature would shift the reaction towards the reactants. Spontaneous reactions can be either endothermic or exothermic, so an increase in temperature does not specifically favor them.

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5.

The equilibrium constant for a given system will change when:
- A.
  
  The temperature changes
- B.
  
  The reactant concentration changes
- C.
  
  The pressure changes
- D.
  
  A catalyst is added
Correct Answer
A. The temperature changes

Explanation
The equilibrium constant for a given system will change when the temperature changes because the equilibrium constant is dependent on the difference in energy between the reactants and products. As the temperature increases, the average kinetic energy of the molecules increases, leading to more collisions and a higher likelihood of successful reactions. This shift in the reaction rate can cause a change in the equilibrium position, resulting in a change in the equilibrium constant.

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6.

A solution that is at equilibrium must be
- A.
  
  Concentrated
- B.
  
  Dilute
- C.
  
  Saturated
- D.
  
  Unsaturated
Correct Answer
C. Saturated

Explanation
A solution that is at equilibrium must be saturated. This is because at equilibrium, the rate of dissolution of solute in the solvent is equal to the rate of precipitation of solute from the solvent. In a saturated solution, the maximum amount of solute has dissolved in the solvent, and any additional solute added will not dissolve. Therefore, a saturated solution is at equilibrium because there is no further dissolution or precipitation occurring.

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7.

When is equilibrium reached in a chemical reaction?
- A.
  
  When the forward reaction stops.
- B.
  
  The reverse reaction stops.
- C.
  
  The concentrations of the reactants and products become equal.
- D.
  
  The rates of the forward and reverse reactions become equal.
Correct Answer
D. The rates of the forward and reverse reactions become equal.

Explanation
Equilibrium is reached in a chemical reaction when the rates of the forward and reverse reactions become equal. This means that the reaction is happening at the same rate in both directions, resulting in no net change in the concentrations of the reactants and products over time. At equilibrium, the system is in a state of balance, with the concentrations of the reactants and products remaining constant.

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8.

For a system at equilibrium, lowering the temperature will always:
- A.
  
  Increase the rate of the reaction
- B.
  
  Increase the concentrations of the products
- C.
  
  Favor the endothermic
- D.
  
  Favor the exothermic
Correct Answer
D. Favor the exothermic

Explanation
Lowering the temperature of a system at equilibrium will favor the exothermic reaction. This is because according to Le Chatelier's principle, a system at equilibrium will shift in a direction that opposes the change imposed on it. By lowering the temperature, the system will try to counteract this decrease by favoring the reaction that releases heat, which is the exothermic reaction. This shift will help maintain equilibrium by counterbalancing the decrease in temperature.

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9.

Which change may occur in a reaction system when a catalyst is addded?
- A.
  
  The potential energy of the reactants increases.
- B.
  
  The potential energy of the products increases.
- C.
  
  The point of equilibrium is reached more rapidly.
- D.
  
  The heat of reaction decreased.
Correct Answer
C. The point of equilibrium is reached more rapidly.

Explanation
When a catalyst is added to a reaction system, it provides an alternative pathway with lower activation energy for the reaction to occur. This means that the reactants can now reach the point of equilibrium more rapidly, as the catalyst speeds up the rate of the reaction without being consumed in the process. Therefore, the correct answer is that the point of equilibrium is reached more rapidly when a catalyst is added to a reaction system.

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