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.

Equilibrium chemical reaction quiz questions

2.

In a reversible reaction, chemical equilibrium is attained when the

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

Correct Answer

A. 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.

Which type of reaction is most favored by an increase in temperature?

Endothermic
Exothermic
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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4.

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

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

Correct Answer

A. 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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5.

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

Increase the rate of the reaction
Increase the concentrations of the products
Favor the endothermic
Favor the exothermic

Correct Answer

A. 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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6.

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

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.

Correct Answer

A. 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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7.

The equilibrium constant for a given system will change when:

The temperature changes
The reactant concentration changes
The pressure changes
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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8.

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

Decreases
Increases
Remains the same

Correct Answer

A. 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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9.

A solution that is at equilibrium must be

Concentrated
Dilute
Saturated
Unsaturated

Correct Answer

A. 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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Equilibrium Chemical Reaction Quiz Questions

When is equilibrium reached in a chemical reaction?

Quiz Preview

In a reversible reaction, chemical equilibrium is attained when the

Which type of reaction is most favored by an increase in temperature?

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

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

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

The equilibrium constant for a given system will change when:

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 solution that is at equilibrium must be