Question

question 1 (1 point)
a system reaches equilibrium. which must be true of the system?
it is open
it is closed
it is either open or closed
it is open and has pressure
it has no pressure

question 2 (1 point)
two substances are mixed together in a flask. they undergo a reaction and reaches chemical equilibrium. which statement is true?
the flask now contains only the products in the reaction.
the flask now contains only the reactants in the reaction.
the flask now contains both the reactants and the products.
the flask now contains neither the reactants nor the products.
the contents of the flask cannot be determined.

question 3 (1 point)
the graph of a reaction showing concentration versus time shows horizontal lines for both the forward and the reverse reaction after a certain period of time. what does this indicate?
the system is open.
the system has reached equilibrium.
the rates of the forward and reverse reactions differ.
there is no molecular interaction.
the concentration of the product is the same as the concentration of the reactants.

Explanation:

Question 1

To determine the correct answer, we recall the concept of a system reaching equilibrium. A system can reach equilibrium whether it is open (where matter or energy can be exchanged, but in some cases like chemical equilibrium in a solution with a constant external condition) or closed (where neither matter nor energy is exchanged freely, but equilibrium can still be achieved). So the system can be either open or closed.

At chemical equilibrium, the forward and reverse reactions occur at the same rate. This means that both reactants and products are present in the system because the reactions haven't stopped, just reached a balance where the concentrations of reactants and products remain constant. So the flask contains both reactants and products.

When a reaction reaches equilibrium, the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant over time. A horizontal line on a concentration - time graph for both forward and reverse reactions (or for reactants and products) indicates that the concentrations are no longer changing, which means the system has reached equilibrium.

Answer:

C. it is either open or closed

Question 2