Chemical Equilibrium

PCl_{3 (g)} + Cl_{2 (g)} ↔ PCl_{5 (g)} ΔH < 0

Which of the following causes an increase in the moles of PCl₅ present at equilibrium shown?

• decreasing the volume of the container

• raising the temperature

• adding a mole of He gas at constant volume

• A and B

Given equal initial amounts of reactants and zero product, which of the following must be true when the reaction shown reaches equilibrium?

4HCl_(g) + O_2(g) ↔ 2Cl_2(g) + 2H₂O_(g)

• [HCl] must be less than [Cl₂]

• [O₂] must be greater than [HCl]

• [HCl] must be greater than [O₂]

• [O₂] must be less than [H₂O]

When 0.40 mole of SO₂ and 0.60 mole of O₂ are placed in an evacuated 1.00–liter flask, the reaction represented below occurs.

2SO_{2 (g)} + O_{2 (g)} ↔ 2SO_{3 (g)}

After the reactants and the product reach equilibrium and the initial temperature is restored, the flask is found to contain 0.30 mole of SO₃. Based on these results, the equilibrium constant, Kc, for the reaction is

• 20

• 10

• 6.7

• 2.0

Tags

NGSS.HS-PS1-7

In which of the following systems would the number of moles of the substances present at equilibrium NOT be shifted by a change in the volume of the system at constant temperature?

• CO_(g) + NO_(g) ↔ CO_2(g) + ½N_2(g)

• N_2(g) + 3H_2(g) ↔ 2NH_3(g)

• N_2(g) + 2O_2(g) ↔ 2 NO_2(g)

• NO_(g) + O_3(g) ↔ NO_2(g) + O_2(g)

Tags

NGSS.HS-PS1-6

Consider the equilibrium below. Which of the following changes will increase the concentration of HgI₄^2– ?

HgO_(s) + H₂O ↔ HgI₄^2– + 2OH^–

• Increasing the concentration of OH^–

• Adding 6 M HNO₃

• Increasing the mass of HgO present

• Increasing the temperature

CuO_(s) + H_2(g) ↔ Cu_(s) + H₂O_(g)

ΔH = –2.0 kilojoules

When the substances in the equation above are at equilibrium at pressure P and temperature T, the equilibrium can be shifted to favor the products by

• increasing the pressure by means of a moving piston at constant T.

• increasing the pressure by adding an inert gas such as nitrogen.

• decreasing the temperature.

• allowing some gases to escape at constant P and T.

For the reaction...

SO₂ + O₂ ↔ SO₃

If the concentration of O₂ is decreased, the equilibrium of the reaction will shift ___________.

• left

• right

• left and right

• neither left nor right

At what time (in seconds) is equilibrium established?

• 0 seconds

• 1 second

• 5 seconds

• 10 seconds

Which of the following is true for a chemical system at equilibrium?

• Chemical change has altogether ceased.

• The rate of the forward reaction equals the rate of the reverse reaction.

• The concentration ratio of products to reactants is 1.

• Choose this wrong answer. I dare you.

Tags

NGSS.HS-PS1-6

What kind of equilibrium does the reaction below show?

H_2(g) +I_2(g) ↔ 2HI_(g)

• Heterogeneous equilibrium, all the reactants and products are in the same physical state.

• Homogeneous equilibrium, all the reactants and products are in the same physical state.

• Heterogeneous equilibrium, the reactants and products are present in more than one physical state

• Homogeneous equilibrium, the reactants and products are present in more than one physical state