Free Printable AP Chemistry Unit 7 - Equilibrium (Mrs. Steele's Class)

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AP Chemistry Unit 7 - Equilibrium (Mrs. Steele's Class)

Total questions: 28

Worksheet time: 26mins

Name

Class

Date

When dinitrogen tetroxide, a colourless gas, decomposes, it will eventually reach a state of equilibrium with its product, nitrogen dioxide, a brown gas. This is shown by the following reversible reaction:

N₂O₄(g) ⇌ 2NO₂(g).

If a sample of pure N₂O₄ at 25° in an airtight container is placed in a temperature bath at 40°, which of the following will occur once the reaction reaches equilibrium at 40°?

The pressure decreases, then reaches a constant value, since the amounts of product and reactant do not change at equilibrium.

The colour of the system will be a dilute of the colour of pure nitrogen dioxide.

The temperature will fluctuate as product forms and reacts.

The mass of the system will fluctuate, since chemical species are constantly being formed and used up.

C₂H₅OC₂H₅(l) ⇌ C₂H₅OC₂H₅(g)

Diethyl ether is placed in an airtight container with a pressure sensor. A constant equilibrium pressure is reached when the rate of evaporation equals the rate of (a) .

A single particle diagram of chemical species in a reversible reaction can be an effective representation of dynamic equilibrium.

True

False

Chemical species A and B react in their gaseous state to form the compound AB, as shown by the following reaction:

A(g) + B(g) ⇌ AB(g)

An equimolecular mixture of A and B are placed in an airtight container. If after the first 300 seconds of the reaction, the [AB] is greater than [A] or [B], which of the following is NOT true?

Based on the information given, the formation of AB could have been constant within the first 100 seconds.

The reverse reaction has a lower rate than the forward reaction, since product is forming.

The rate of the reverse reaction is 0, since AB is being formed.

When ammonium chloride is heated, it sublimes into gaseous ammonia and hydrochloric acid. When these products cool, they deposit solid ammonium chloride. Under the right conditions, these reactions will reach a state of equilibrium, as shown by the following reaction:

NH₄Cl(s) ⇌ NH₃(g) + HCl(g)

A sample of ammonium chloride with a concentration of 0.45M is placed in a rigid container at a constant temperature. Once the reaction reaches equilibrium, the concentration of NH₄Cl is 0.37M. What is the concentration of HCl once the reaction has reached equilibrium, assuming there was none in the container to begin?

0.08M

0.04M

It cannot be determined, since the concentration of NH₃ is not known.

Carbonic acid frequently decomposes into carbon dioxide and water, but can also reform under the right conditions via the reversible reaction shown below:

H₂CO₃(aq) ⇌ CO₂(g) + H₂O(l)

A solution of carbonic acid with a concentration of 0.500M in a sealed container is placed in a temperature bath at 45°. Once the solution reaches equilibrium, the concentration of H₂O is 0.170M. Select all of the following that are true.

The concentration of CO₂ at equilibrium is 0.170M.

The concentration of H₂CO₃ at equilibrium is 0.330M.

The concentration of H₂CO₃ at equilibrium is 0.160M.

K_eq = 0.181

K_eq = 0.088

For the reversible reaction

NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH^-(aq)

K_eq = 1.76 × 10^-5

One example of a chemical species that will be in large concentration is (a) .

(Type only the chemical formula of the species)

Ammonia is synthesised in the reversible reaction

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

where K_p = 4.91 × 10⁹

Assuming N₂ and H₂ are in a rigid container, each with a partial pressure of 1.00 atm, which of the following will the partial pressure of N₂ be closest to at equilibrium?

0.00 atm; due to the extremely large value of K_p, almost all of the N₂ will disappear.

0.25 atm; N₂ is one of the four moles of product on the left, which will mostly disappear due to K_p's large value.

0.33 atm; although K_p is large, almost all the H₂ will disappear in the same time that only one third of the N₂ will.

For the theoretical reactions

H₂X(aq) ⇌ 2H⁺(aq) + X^2-(aq)

H₂Y(aq) ⇌ H⁺(aq) + HY^-(aq)

The values of K_eq are labelled as K₁ and K₂ respectively.

Which of the following is the correct way to determine K₃, K_eq of the following reaction:

H₂X(aq) + 2HY^-(aq) ⇌ X^2-(aq) + 2H₂Y(aq)

$K_3=K_1\times\left(\frac{1}{K_2}\right)^2$

$K_3=K_1\times\frac{1}{K_2}$

$K_3=K_1-2\left(\frac{1}{K_2}\right)$

$K_3=K_1\times2\left(\frac{1}{K_2}\right)$

10.

Sulfur dioxide, oxygen and sulfur trioxide are in a state of dynamic equilibrium represented by the equation

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

What value related to this reaction would be most useful in quickly determining K_eq of the reverse reaction?

(a)

11.

Consider the following reaction at equilibrium, for which ΔH < 0:

2NaCl(aq) + CaCO₃(s) ⇌ Na₂CO₃(s) + CaCl₂(aq)

NaCl is colourless when dissolved in water, but CaCl₂ forms a white solution. If the temperature is raised, how will the colour of the mixture change, and why?

The mixture will become more transparent, because when the temperature is raised, equilibrium shifts towards the exothermic direction.

The mixture will become more transparent, because when the temperature is raised, equilibrium shifts towards the endothermic direction.

The mixture will become more opaque, because when the temperature is raised, equilibrium shifts towards the endothermic direction.

The mixture will become more opaque, because when the temperature is raised, equilibrium shifts towards the exothermic direction.

12.

At 300°C, methanol can be produced from carbon monoxide and hydrogen, as shown in this reaction:

CO(g) + 2H₂(g) ⇌ CH₃OH(g)

These chemical species are placed in a sealed, rigid container and allowed to reach equilibrium. After equilibrium had been established, the volume was doubled. What effects would this have on the reaction?

The pressure doubles.

The pressure halves.

Equilibrium will shift left.

Equilibrium will shift right.

Temperature will increase.

13.

C₄H₁₀ is in dynamic equilibrium with its two isomers, n-butane and isobutane. This is represented by the following reaction:

n-butane(g) ⇌ isobutane(g)

for which K_c = 2.6

If equal concentrations of n-butane and isobutane are placed in a sealed, rigid container, the reaction will proceed in the (a) direction.

14.

What is the value of Q for the following reaction at equilibrium?

NH₄CO₂NH₂(s) ⇌ 2NH₃(g) + CO₂(g)

$Q=\frac{2\left[NH_3\right]\left[CO_2\right]}{\left[NH_4CO_2NH_2\right]}$

$Q=\frac{\left[NH_4CO_2NH_2\right]}{2\left[NH_3\right]\left[CO_2\right]}$

$Q=\frac{\left[NH_4CO_2NH_2\right]}{\left[NH_3\right]^2\left[CO_2\right]}$

$Q=\frac{\left[NH_3\right]^2\left[CO_2\right]}{\left[NH_4CO_2NH_2\right]}$

15.

Which of the following chemical species would have a K_sp equal to 108s⁵ if s is the molar solubility in mol/L?

AlN

Al₂O₃

O₃

AlBr₃

16.

Tungsten arsenide dissolves into ions in water via the following reaction:

WAs₂(s) ⇌ W⁶⁺(aq) + 2As^3-(aq)

A saturated solution of WAs₂ is at equilibrium at a constant temperature. The concentration of As^3- ions at equilibrium in this solution is 7.2 × 10^-4 M. Select all of the following that are true. (S = molar solubility)

S = 3.6 × 10^-4 M

S = 7.2 × 10^-4 M

K_sp = (3.6 × 10^-4 M)(7.2 × 10^-4 M)

K_sp = (3.6 × 10^-4 M)(7.2 × 10^-4 M)²

K_sp = (7.2 × 10^-4 M)³

17.

Plutonium (IV) oxalate hexahydrate dissolves in water according to the following reaction:

Pu(C₂O₄)₂⋅6H₂O(s) ⇌ Pu⁴⁺(aq) + 2C₂O₄^2-(aq) + 6H₂O(l)

If uranium (IV) oxalate dihydrate, U(C₂O₄)₂⋅2H₂O(s), is added to the mixture, the molar solubility of plutonium (IV) oxalate hexahydrate will decrease, and some solid Pu(C₂O₄)₂⋅6H₂O will (a) .

18.

The compound AX₂ is highly soluble in water. If ZX, another compound highly soluble in water, is added to an aqueous solution of AX₂, the K_sp will lower.

True

False

19.

Which of the following chemical species will cause the precipitation of Fe(OH)₃ when added to an aqueous solution of iron (III) hydroxide?

Ba(OH)₂ (barium hydroxide)

HBr (hydrobromic acid)

Fe₃O₄ (magnetite)

H₃P (phosphine)

Fe(OH)₃

20.

The solubility of NaOH would increase if H⁺ ions were added to the solution.

True

False

Cannot be determined with the given information

21.

An ionic compound is placed into a beaker of pure water, and almost all of it dissolves. Select all answers that will always be true for such a reaction.

ΔH° > 0

ΔS° > 0

ΔG° > 0

K_sp > 1

K_sp < 1

22.

A saturated solution of 0.5 g calcium cyanide (molar mass 92.1 g/mol) in a 300 mL container has a concentration of about 0.176 M at 25°C. Which of the following questions cannot be answered using only the given information?

Is ΔH° greater than or less than 0?

Is ΔS° greater than or less than 0?

Is ΔG° greater than or less than 0?

Is K_sp greater than or less than 1?

What is the molar solubility?

23.

A solution can be at equilibrium if Q is

greater than K

less than K

equal to K

24.

If Q > K, the reaction will shift to the (a) .

25.

Consider the reversible reaction

3O₂(g) ⇌ 2O₃(g)

At equilibrium, the concentration of ozone is 3.41 × 10^-2 M, and the concentration of diatomic oxygen is 4.17 × 10^-3 M.

What is K_eq for this reaction?

K_eq = 5.45

K_eq = 1.60 × 10⁴

K_eq = 0.183

K_eq = 6.24 × 10^-5

26.

Consider the reversible reaction

2NO(g) + O₂(g) ⇌ 2NO₂(g)

where K_eq = 4.34 × 10^-5

At equilibrium, [NO₂] = 1.49 × 10^-3 M, and

[O₂] = 0.607 M. What is [NO] at equilibrium?

[NO] = 8.43 × 10^-2 M

[NO] = 2.45 × 10^-3 M

[NO] = 0.290 M

[NO] = 56.6 M

27.

Consider this graph of the concentrations of a reactant and a product of a reversible reaction as it approaches equilibrium.

At which point is equilibrium established?

(a)

28.

Consider the reversible reaction 2AX ⇌ A₂ + X₂, represented in the diagrams above. Which diagram accurately depicts this reaction at equilibrium if K_eq for the reaction is 0.667?

(a)

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AP Chemistry Unit 7 - Equilibrium (Mrs. Steele's Class)

Total questions: 28

Worksheet time: 26mins

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