Equilibrium

Which statement describes a reaction at equilibrium?

• The mass of the products must equal the mass of the reactants.

• The entropy of the reactants must equal the entropy of the products.

• The rate of formation of the products must equal the rate of formation of the reactants.

• The number of moles of the reactants must equal the number of moles of the products.

For a chemical system at equilibrium, the concentrations of both the reactants and the products must

• decrease

• increase

• be constant

• be equal

Equilibrium can be reached by

• physical changes, only

• nuclear changes, only

• both physical changes and chemical changes

• both nuclear changes and chemical changes

Which equation represents a chemical equilibrium?

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When a reversible reaction is at equilibrium, the concentration of products and the concentration of reactants must be

• decreasing

• increasing

• constant

• equal

What occurs when a reaction reaches equilibrium?

• The concentration of the reactants increases.

• The concentration of the products increases.

• The rate of the forward reaction is equal to the rate of the reverse reaction.

• The rate of the forward reaction is slower than the rate of the reverse reaction.

Given the diagram representing a closed system at constant temperature: Which statement describes this system at equilibrium?

• The mass of H₂O(l) equals the mass of H₂O(g)

• The volume of H₂O(l) equals the volume of H₂O(g).

• The number of moles of H₂O(l) equals the number of moles of H₂O(g).

• The rate of evaporation of H₂O(l) equals the rate of condensation of H₂O(g).

Given the equation representing a phase change at equilibrium:

C₂H₅OH(l) <---> C₂H₅OH(g)

Which statement is true?

• The forward process proceeds faster than the reverse process

• The reverse process proceeds faster than the forward process

• The forward and reverse processes proceed at the same rate.

• The forward and reverse processes both stop.

Some solid KNO₃ remains at the bottom of a stoppered flask containing a saturated KNO₃(aq) solution at 22°C. Which statement explains why the contents of the flask are at equilibrium?

• The rate of dissolving is equal to the rate of crystallization.

• The rate of dissolving is greater than the rate of crystallization.

• The concentration of the solid is equal to the concentration of the solution.

• The concentration of the solid is greater than the concentration of the solution.

Which balanced equation represents a phase equilibrium?

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