Equilibrium

N₂O₄(g)⇄2NO₂(g)

The graph above represents the data collected under certain conditions for the decomposition of N₂O₄(g) according to the chemical equation above. Based on the graph, at approximately which time is equilibrium established?

• At time A, because N₂O₄(g) is expanding to fill the container.

• At time B, because the reaction is reversible and [NO₂]=[N₂O₄].

• At time C, because the reaction is about to reach completion and [NO₂]>[N₂O₄].

• At time D, because there are no observable changes in [NO₂] and [N₂O₄].

Tags

NGSS.HS-PS1-7

A sample of acetone is placed into a container. The container is sealed and attached to a pressure sensor, as shown in the diagram above. The container is allowed to sit on the lab table for a few minutes as the pressure in the container is monitored at regular intervals. At the end of 2.00 minutes, some acetone liquid remains in the container. Which of the following best explains the pressure data presented in the table above?

• The acetone heats up over time, causing more of it to vaporize at an increasing rate.

• The acetone has completely vaporized after 1.50 minutes, so the pressure becomes constant.

• The acetone vaporizes from the liquid at a constant rate and the rate of condensation increases until it becomes equal to the rate of evaporation and the pressure stays constant.

• The acetone vaporizes from the liquid at a rate that is fast in the beginning but then slows down until the vaporization process stops completely.

Tags

NGSS.HS-PS1-5

NGSS.HS-PS3-4

Brown.... Colorlesss

2NO₂(g)⇄N₂O₄(g)

A sample of pure NO₂(g) in a sealed tube at 20°C is placed in a temperature bath at 30°C. Observations of changes in the color, pressure, and mass of the mixture are recorded as a function of time. Which of the following is an observation that would best support the claim that the reaction represented above has reached equilibrium at 30°C?

• The total mass of the system remains constant because at equilibrium the amounts of reactant and product do not change with time.

• The color of the system changes from brown to completely colorless because at equilibrium only the product will be present.

• The total pressure of the system decreases then reaches a constant value because at equilibrium the amounts of reactant and product no longer change.

• The temperature of the system remains constant because at equilibrium the temperature must be constant.

AgCl(s)⇄Ag⁺(aq)+Cl⁻(aq)

When AgCl(s) is placed in water, it dissolves according to the chemical equation above. The particle diagram above was proposed to represent an aqueous solution in which AgCl(s)

AgCl(s) is in equilibrium with its ions. Which of the following best explains whether or not the diagram provides a good representation of this dynamic equilibrium at the microscopic level?

• It is a good representation because it shows that the dipoles of the H₂O molecules are oriented around the Ag⁺ and Cl⁻ ions in solution.

• It is a good representation because it shows that the concentrations of Ag⁺ ions and Cl⁻ ions are equal at equilibrium.

• It is not a good representation because it does not show that the concentration of AgCl(s) is constant at equilibrium.

• It is not a good representation because it does not illustrate the dynamic equilibrium in which the rates of the forward and reverse reactions are equal.

• The particle diagram does not indicate that the system is at equilibrium because it shows the system only at one point in time.

• The particle diagram indicates that the system is at equilibrium because the value of KK is small.

X(g)+Y(g)⇄XY(g)

The particle diagrams above show the changes that occurred after an equimolecular mixture of X(g) and Y(g) was placed inside a rigid container at constant temperature. Which of the following statements is be best supported by the particle diagrams?

• The rate of the reverse reaction is zero because the concentration of XY keeps increasing.

• The reverse reaction has a higher rate than the forward reaction between 200s and 300s because [XY]>>[X].

• The forward reaction has a faster rate than the reverse reaction between 0s and 300s because more products were being formed.

• The rates of the forward and reverse reactions were the same after 100s because the rate of formation of XY was constant.

Tags

NGSS.HS-PS1-5

In an experiment involving the reaction shown above, a sample of pure HI was placed inside a rigid container at a certain temperature. The table above provides the initial and equilibrium concentrations for some of the substances in the reaction. Based on the data, which of the following is the value of the equilibrium constant (Keq) for the reaction, and why?

SO₂(g)+Cl₂(g)⇄SO₂Cl₂(g)

SO₂(g) reacts with Cl₂(g) to produce SO₂Cl₂(g), according to the equation above. A mixture of 1.00atm of SO₂(g) and 1.00atm of Cl₂(g) is placed in a rigid, evacuated 1.00L container, and the reaction mixture is allowed to reach equilibrium at a certain temperature. The table above shows the initial partial pressure of each gas and the equilibrium partial pressures of SO₂(g) and SO₂Cl₂(g) at the same temperature.

Which of the following indicates the equilibrium value of P_Cl2 and the approximate value of the equilibrium constant Kp ?

• P_Cl2=0.10atm and Kp=5.0

• P_Cl2=0.20atm and Kp=0.050

• P_Cl2=0.20atm and Kp=20.

• P_Cl2=0.80atm and Kp=0.025

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-2

The diagram above represents the equilibrium between two isomers of 2-butene. The equilibrium constant, Kc, is 1.2 at a certain temperature. Two identical vessels each contain an equilibrium mixture of the two gases at that temperature. The concentration of cis‑2‑butene in the second vessel is twice the concentration in the first vessel. What is the concentration of trans‑2‑butene in the second vessel compared to that in the first vessel?

• Half the concentration of that in the first vessel

• The same concentration as that in the first vessel

• Twice the concentration of that in the first vessel

• Four times the concentration of that in the first vessel

Tags

NGSS.HS-PS1-7