Effect of Temperature on Reaction Rate questions

To increase the rate of a chemical reaction, it is necessary to ..........

1. A decrease the rate of collisions between the molecules.
2. B increase the number of non-activated molecules.
3. C decrease the number of activated molecules.
4. D increase the percentage of activated molecules.

Which of the following explains the increase in the rate of reaction when the temperature is raised?
(energy of the reactant particles / rate of collisions of the reactant particles)

1. A stays the same / stays the same
2. B increases / increases
3. C stays the same / increases
4. D increases / stays the same

In which of the following samples do the iron atoms have the highest kinetic energy?

1. A 5 g (at 10°C)
2. B 10 g (at 25°C)
3. C 5 g (at 127°C)
4. D 10 g (at 0°C)

If the rate of a chemical reaction (at 20°C) equals 3.2 × 10⁻³ mol/s, then (at 30°C) it becomes ..........

1. A 1.28 × 10⁻² mol/s
2. B 6.4 × 10⁻³ mol/s
3. C 9.6 × 10⁻³ mol/s
4. D 3.2 × 10⁻⁴ mol/s

When the temperature of a chemical reaction is raised by 50°C, its rate increases by about ..........

1. A 16 times.
2. B 20 times.
3. C 32 times.
4. D 50 times.

The following figures represent the energy diagrams of three different reactions:
Which of the following represents the order of these reactions from the slowest to the fastest?

1. A (2) → (3) → (1)
2. B (1) → (2) → (3)
3. C (3) → (1) → (2)
4. D (2) → (1) → (3)

A piece of a metal reacts with an acid to produce hydrogen gas.
Which of the following leads to an increase in the rate of the reaction?
(heating / grinding the piece of metal / adding water to the acid)

1. A ✓ / ✓ / ✗
2. B ✓ / ✗ / ✓
3. C ✗ / ✓ / ✓
4. D ✓ / ✓ / ✓

All of the following increase the rate of the reaction of 100 mL of 1 M HCl acid with 2 g of calcium carbonate pieces, except ..........

1. A adding 50 mL of distilled water to the acid.
2. B increasing the concentration of the acid to 2 M
3. C heating the acid before adding it to the calcium carbonate.
4. D changing the calcium carbonate pieces into powder.

In the opposite reversible reaction: ½H₂(g) + ½I₂(v) ⇌ HI(g)
the activation energy of the forward reaction is 167 kJ and the activation energy of the reverse reaction is 139 kJ
What is the type of this reaction, and what is the value of its change in heat content ΔH?

1. A Exothermic / −28 kJ
2. B Exothermic / +28 kJ
3. C Endothermic / −28 kJ
4. D Endothermic / +28 kJ

In a reversible reaction, the activation energy of the endothermic forward reaction was 50 kJ and its ΔH was 20 kJ
What is the activation energy of the reverse reaction of the same reaction?

1. A 20 kJ
2. B 30 kJ
3. C 50 kJ
4. D 70 kJ

The following table shows the results of two experiments in which the same number of moles of zinc reacted with the same volume of hydrochloric acid:
Experiment (1) : Zn strip , temperature 10°C , [HCl] = 10 M , volume of H₂ produced 10.6 mL
Experiment (2) : Zn powder , temperature 15°C , [HCl] = 3 M , volume of H₂ produced 7.3 mL
Which factor explains the difference between the volume of H₂ produced in experiment (1) and that in experiment (2)?

1. A [HCl].
2. B Temperature.
3. C Nature of the reactants.
4. D Surface area of Zn

You have 4 glass beakers, each containing 2 g of magnesium strip reacting with 100 mL of dilute hydrochloric acid under the conditions written on each beaker.
In which of the following beakers is the rate of the reaction as great as possible?

1. A A
2. B B
3. C C
4. D D

The opposite table shows the conditions of two experiments.
First experiment: Fe filings with concentrated HNO₃ , at 20°C
Second experiment: Fe pieces with dilute HNO₃ , at 10°C
Which experiment produces the smallest volume of gas, and what is the factor affecting that?

1. A The first experiment / nature of the reactants.
2. B The second experiment / temperature.
3. C The first experiment / concentration of the acid.
4. D The second experiment / nature of the reactants.

From the opposite graph: if temperature (A) equals 40°C,
what is temperature (B)?

1. A 60°C
2. B 70°C
3. C 50°C
4. D 90°C

The following reaction was carried out at two different temperatures without changing the concentration of the reactants:
C₂H₅Br(aq) + OH⁻(aq) → C₂H₅OH(aq) + Br⁻(aq)
From the opposite graph: which reaction has the greatest rate,
and which reaction takes place at the higher temperature?

1. A (A) , (A)
2. B (A) , (B)
3. C (B) , (A)
4. D (B) , (B)

In the opposite graph, curve (X) represents the volume of gas produced from the reaction between 2 g of zinc granules and excess of an acid (at 25°C).
What change leads to the formation of curve (Y) when the experiment is repeated?

1. A Using 1 g of zinc powder (at 25°C).
2. B Using 2 g of zinc powder (at 30°C).
3. C Using 1 g of zinc granules (at 25°C).
4. D Using 2 g of zinc granules (at 30°C).

Curve (X) in the opposite graph shows the volume of hydrogen gas given off with time when 0.01 mol of zinc powder is added to 100 mL of 0.1 M hydrochloric acid (at 25°C).
Which curve represents the volume of hydrogen gas given off with time when the previous experiment is repeated using 0.01 mol of zinc powder with 100 mL of 0.2 M hydrochloric acid (at 50°C)?

1. A (A).
2. B (B).
3. C (C).
4. D (D).

The rate of the reaction of zinc powder with 0.1 M HCl acid is greater than the rate of the reaction of the same mass of zinc pieces with the same acid, because ..........

1. A its activation energy is lower.
2. B its activation energy is higher.
3. C the number of reacting molecules per unit time is greater.
4. D ΔH of the reaction is lower.

The rate of reaction is the fastest in experiment ..........

1. A A
2. B B
3. C C
4. D D

Which of the following graphs represents an exothermic reaction with a higher activation energy?

1. A A
2. B B
3. C C
4. D D

From the opposite energy diagram:
Which of the following represents the activation energy of each of the forward reaction (X) and the reverse reaction (Y)?

1. A (X) : A , (Y) : C
2. B (X) : A , (Y) : D
3. C (X) : B , (Y) : C
4. D (X) : B , (Y) : D

The opposite energy diagram represents a chemical reaction.
What is the activation energy of its reverse reaction?

1. A 30 kJ
2. B 140 kJ
3. C 170 kJ
4. D 200 kJ

A reversible chemical reaction has ΔH for its forward path = −150 kJ/mol and an activation energy of its reverse path = 350 kJ/mol
What is the activation energy of its forward path?

1. A +500 kJ/mol
2. B +200 kJ/mol
3. C +150 kJ/mol
4. D −200 kJ/mol

Which figure represents the energy path of an exothermic reaction whose activation energy equals 50 kJ and whose ΔH equals −100 kJ?

1. A A
2. B B
3. C C
4. D D

In the opposite equilibrium reaction: N₂O₄(g) + 58 kJ ⇌ 2NO₂(g)
What happens when the temperature of the system is lowered?

1. A [NO₂] increases
2. B [N₂O₄] decreases
3. C The intensity of the reddish-brown colour increases.
4. D The intensity of the reddish-brown colour decreases.

Which of the following represents the conditions that make an exothermic equilibrium reaction proceed in the direction of forming the products?
(lowering the temperature / removing one of the products)

1. A ✗ / ✓
2. B ✓ / ✓
3. C ✓ / ✗
4. D ✗ / ✗

A reversible reaction in a state of equilibrium proceeds in the reverse direction when the temperature is raised.
Which of the following describes the forward reaction?

1. A An exothermic reaction whose ΔH has a positive sign.
2. B An exothermic reaction whose ΔH has a negative sign.
3. C An endothermic reaction whose ΔH has a positive sign.
4. D An endothermic reaction whose ΔH has a negative sign.

In the equilibrium reaction: SO₂Cl₂(g) + Energy ⇌ SO₂(g) + Cl₂(g)
When the temperature is lowered, the system shifts to the ..........

1. A left and [SO₂Cl₂] increases.
2. B left and [SO₂Cl₂] decreases.
3. C right and [SO₂Cl₂] increases.
4. D right and [SO₂Cl₂] decreases.

All of the following agree with Le Chatelier's principle, except ..........
(type of reaction / change in temperature / effect on Kc of the reaction / the system shifts to the)

1. A endothermic / lowered / decreases / left
2. B endothermic / raised / increases / right
3. C exothermic / raised / increases / right
4. D exothermic / lowered / increases / right

In the reaction of preparing ammonia gas from its elements:
What is the effect of raising the temperature on the equilibrium system?

1. A The production of NH₃ gas decreases
2. B There is no change in the amount of NH₃ gas produced.
3. C The concentration of N₂ gas decreases
4. D There is no change in the amount of N₂ gas consumed.

In the opposite equilibrium reaction: SO₃(g) ⇌ SO₂(g) + ½O₂(g) ΔH° = +43 kJ
What is the effect of increasing the temperature of the equilibrium system?

1. A The rate of the forward reaction decreases, the rate of the reverse reaction increases and the equilibrium constant decreases.
2. B The rate of the forward reaction increases more than the rate of the reverse reaction, and the equilibrium constant does not change.
3. C The rate of the forward reaction increases more than the rate of the reverse reaction, and the equilibrium constant increases.
4. D Both the rate of the forward reaction and the rate of the reverse reaction decrease, and the equilibrium constant does not change.

Two experiments were carried out to determine the change in the value of Kc of reversible reactions with temperature, and the results were recorded in the following two tables:
Results (1) : at 25°C , Kc = 4 × 10⁻² , at 127°C , Kc = 1.4 , at 227°C , Kc = 41
Results (2) : at 25°C , Kc = 4.2 × 10⁸ , at 127°C , Kc = 4.5 × 10⁴ , at 227°C , Kc = 62
Which of the following represents each of the two reactions (1) and (2)?

1. A (1) : N₂O₄(g) ⇌ 2NO₂(g) , (2) : N₂H₄(g) ⇌ N₂(g) + 2H₂(g) ΔH = (−)
2. B (1) : N₂H₄(g) ⇌ N₂(g) + 2H₂(g) ΔH = (−) , (2) : N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
3. C (1) : N₂O₄(g) ⇌ 2NO₂(g) , (2) : 2SO₃(g) ⇌ 2SO₂(g) + O₂(g) ΔH = (+)
4. D (1) : N₂(g) + 3H₂(g) ⇌ 2NH₃(g) , (2) : 2SO₃(g) ⇌ 2SO₂(g) + O₂(g) ΔH = (+)

From the reversible reaction: 2H₂(g) + CO(g) ⇌ CH₃OH(v)
Which of the following represents the equilibrium constant of this reaction?

1. A Kp = (2P_H₂)² × (P_CO) / (P_CH₃OH)
2. B Kp = (P_H₂)² × (P_CO) / (P_CH₃OH)
3. C Kp = (P_CH₃OH) / ((P_H₂)² × (P_CO))
4. D Kp = (P_CH₃OH) / ((2P_H₂)² × (P_CO))

In the equilibrium reaction: 2A(g) + B(g) ⇌ C(g) (at 392°C)
If the partial pressures of the reactants and products at equilibrium are as in the opposite table:
(A) : 6.7 atm , (B) : 10.1 atm , (C) : 3.6 atm
What is the approximate value of Kp for this reaction at equilibrium?

1. A 8 × 10⁻³
2. B 5.32 × 10⁻³
3. C 0.146
4. D 54.5

At the equilibrium of the reaction mixture: N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
the partial pressure of N₂ gas was 18.75 pressure units, the partial pressure of H₂ gas was 2.5 pressure units, and the total pressure of the mixture was 25 pressure units. What is the value of Kp for this equilibrium system?

1. A 1.2 × 10⁻⁴
2. B 0.048
3. C 0.075
4. D 21

In the reaction of preparing ammonia gas from its elements, the partial pressures of nitrogen, hydrogen and ammonia at equilibrium were a , b and c respectively. Which of the following represents Kp for this reaction?

1. A c² / (a³b)
2. B a³b / c²
3. C ab³ / c²
4. D c² / (ab³)

Which of the following describes the following reaction: 2H₂(g) + O₂(g) ⇌ 2H₂O(v)?

1. A All collisions between H₂ and O₂ molecules lead to the formation of H₂O
2. B The total pressure of the reaction equals the sum of the partial pressures of the gases H₂ , O₂ and H₂O at equilibrium.
3. C The rate of formation of H₂O equals the rate of consumption of O₂
4. D The value of Kp is constant when the temperature is raised.

The opposite graph shows the percentage of the product under different conditions for the forward direction of a reaction that is ..........

1. A exothermic, and the number of moles of its products is less than the number of moles of the reactants.
2. B exothermic, and the number of moles of its products is greater than the number of moles of the reactants.
3. C endothermic, and the number of moles of its products is less than the number of moles of the reactants.
4. D endothermic, and the number of moles of its products is greater than the number of moles of the reactants.

In which of the following reactions does the product of the forward reaction increase by increasing the temperature and lowering the pressure?

1. A CH₄(g) + H₂O(v) ⇌ 3H₂(g) + CO(g) ΔH = +206 kJ
2. B 4NH₃(g) + 3O₂(g) ⇌ 2N₂(g) + 6H₂O(v) ΔH = −227 kJ
3. C 2NO₂(g) ⇌ N₂O₄(g) ΔH = −58 kJ
4. D 3O₂(g) ⇌ 2O₃(g) ΔH = +143 kJ

Which of the following reactions is activated in the forward direction when the pressure is increased?

1. A PCl₅(g) ⇌ PCl₃(g) + Cl₂(g)
2. B N₂(g) + O₂(g) ⇌ 2NO(g)
3. C H₂(g) + I₂(g) ⇌ 2HI(g)
4. D 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

From the reaction: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g) + Heat
its speed can be increased by ..........

1. A increasing the pressure.
2. B lowering the pressure.
3. C raising the temperature.
4. D lowering the temperature.

In the equilibrium process: N₂O₄(g) + 58 kJ ⇌ 2NO₂(g)
the reaction shifts to the right when ..........

1. A NO₂ is added
2. B N₂O₄ is removed
3. C the temperature is lowered.
4. D the volume of the system is increased.

From the opposite equation: 2H₂O(v) ⇌ 2H₂(g) + O₂(g) ΔH = +484 kJ
Which of the following leads to an increase in the volume of hydrogen gas produced?

1. A Raising the temperature.
2. B Lowering the temperature.
3. C Increasing the pressure.
4. D Adding more O₂ gas

Kp for the following equilibrium reaction: H₂(g) + I₂(g) ⇌ 2HI(g) (at 444°C , 1 atm) equals 50
What is the value of Kp for the same reaction (at 444°C , 2 atm)?

1. A 25
2. B 50
3. C 100
4. D 200

The compound PCl₅ decomposes in a closed vessel according to the equation: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) Kp = 16
What is the value of Kp for this reaction when the volume of the reaction vessel is halved?

1. A 8
2. B 16
3. C 32
4. D 64

The opposite reversible reaction was carried out in a closed vessel at constant temperature: AX₃(g) + X₂(g) ⇌ AX₅(g)
All of the following are correct when the system is at equilibrium, except ..........

1. A The rate of formation of X₂ equals the rate of formation of AX₃
2. B Increasing the volume of the vessel leads to producing more AX₅
3. C Increasing the pressure leads to producing more AX₅
4. D The compound AX₃ remains present in the reaction space.

In the opposite equilibrium reaction the temperature was raised: H₂(g) + I₂(v) ⇌ 2HI(g) − Heat
What is the effect of that on the value of Kp of the reaction and on the position of equilibrium?

1. A The value of Kp decreases and the position of equilibrium shifts to the left.
2. B The value of Kp increases and the position of equilibrium shifts to the right.
3. C The value of Kp does not change and the position of equilibrium shifts to the left.
4. D The value of Kp decreases and the position of equilibrium does not change.

The following reaction was carried out at normal atmospheric pressure: X(g) + 3Y(g) ⇌ 2Z(g)
At temperature T₁, Kp for the reaction was 2
At a higher temperature T₂, the partial pressures of the reactants and products at equilibrium were as in the opposite table: (X) : 2 atm , (Y) : 3 atm , (Z) : 5 atm
What is the value of Kp at temperature T₂, and what is the type of the forward reaction?

1. A 54/25 / endothermic.
2. B 54/25 / exothermic.
3. C 25/54 / endothermic.
4. D 25/54 / exothermic.

What role does the catalyst play in a chemical reaction?

1. A It increases the amount of the products.
2. B It decreases the activation energy needed for the reaction.
3. C It increases the kinetic energy of the molecules.
4. D It decreases the internal energy of the products.

A catalyst is a chemical substance that ..........

1. A increases the concentration of the products at equilibrium.
2. B changes the equilibrium constant of the chemical reaction.
3. C decreases the time needed to reach the state of equilibrium.
4. D supplies the chemical reaction with energy.

The opposite energy diagram is for a chemical reaction.
What is the effect of adding a catalyst on the values of both the activation energy Ea and the enthalpy of the reaction ΔH?

1. A Ea : decreases , ΔH : decreases.
2. B Ea : decreases , ΔH : does not change.
3. C Ea : does not change , ΔH : decreases.
4. D Ea : decreases , ΔH : increases.

Adding vanadium pentoxide to the mixture of O₂ and SO₂ during the preparation of sulphuric acid leads to ..........

1. A changing the path of the reaction while lowering the activation energy of the reaction.
2. B changing the path of the reaction while increasing the activation energy of the reaction.
3. C the reaction proceeding along the same path while increasing the activation energy of the reaction.
4. D the reaction proceeding along the same path while lowering the activation energy of the reaction.

Which of the following describes a catalyst?

1. A It changes the path of the reaction by increasing the activation energy.
2. B It increases the rate of reaction by lowering its value of ΔH.
3. C It increases the percentage of particles that have the minimum energy needed for the reaction.
4. D It changes the amount of the products at the end of the reaction.

The compound MnO₂ is used as a catalyst in the decomposition of hydrogen peroxide, and the rate of the reaction decreases with time, because ..........

1. A MnO₂ is consumed.
2. B the reaction absorbs energy from the surroundings.
3. C the surface area of MnO₂ decreases.
4. D the hydrogen peroxide becomes dilute.

From the opposite reaction: 2CO(g) + 2NO(g) → 2CO₂(g) + N₂(g)
Which of the following represents the type of this reaction and where it takes place?

1. A Neutralization reaction / in the blast furnace.
2. B Oxidation-reduction reaction / in the catalytic converter.
3. C Neutralization reaction / in the catalytic converter.
4. D Oxidation-reduction reaction / in the blast furnace.

In the reversible reaction: Cl(g) + O(g) + O₃(g) ⇌ 2O₂(g) + Cl(g)
What is the catalyst used in this reaction, and what role does it play?

1. A O / increasing the rate of the forward reaction only.
2. B Cl / increasing the rate of the forward reaction only.
3. C O / increasing the rates of both the forward and reverse reactions.
4. D Cl / increasing the rates of both the forward and reverse reactions.

A reaction takes place in two steps, as follows:
(1) S₂O₈²⁻(aq) + 2I⁻(aq) + 2Fe²⁺(aq) → 2SO₄²⁻(aq) + 2I⁻(aq) + 2Fe³⁺(aq)
(2) 2SO₄²⁻(aq) + 2I⁻(aq) + 2Fe³⁺(aq) → 2SO₄²⁻(aq) + I₂(aq) + 2Fe²⁺(aq)
Which ion acts as the catalyst in this reaction?

1. A Fe²⁺(aq)
2. B I⁻(aq)
3. C SO₄²⁻(aq)
4. D S₂O₈²⁻(aq)

The opposite graph represents the reaction of excess CaCO₃ with HCl acid
Which of the following represents the change in the rate of the reaction with time?

1. A It decreases, because the concentration of the acid decreases.
2. B It decreases, because the concentration of CaCO₃ decreases.
3. C It increases, because the temperature rises.
4. D It increases, because the CO₂ produced acts as a catalyst.

What is the effect of a catalyst on the activation energy of a reversible reaction?

1. A It decreases the activation energy of the forward reaction only.
2. B It decreases the activation energy of the reverse reaction only.
3. C It decreases the activation energy of both the forward and reverse reactions.
4. D It decreases the activation energy of the forward reaction and increases the activation energy of the reverse reaction.

When a suitable catalyst is added to hydrogen peroxide, it decomposes according to the following equation: 2H₂O₂(aq) → 2H₂O(l) + O₂(g)
All of the following describe the rate of this reaction, except ..........

1. A The rate of decomposition of H₂O₂ equals the rate of formation of H₂O
2. B Lowering [H₂O₂] decreases the rate of formation of O₂
3. C Raising the temperature increases the rate of formation of O₂
4. D Increasing the amount of the catalyst decreases the rate of formation of O₂

Two experiments were carried out to measure the rate of the reaction of excess copper(II) carbonate with 20 mL of nitric acid, as shown in the opposite graph.
What change was made to the experiment represented by curve (P) that led to the results represented by curve (Q)?

1. A Using a catalyst.
2. B Adding more copper(II) carbonate.
3. C Using 20 mL of nitric acid of a higher concentration.
4. D Raising the temperature.

Two experiments were carried out on the decomposition of 100 mL of 1 M hydrogen peroxide using two different catalysts, and the opposite graph shows the relation between the rate of reaction and time for each experiment.
Which of the following shows the relation between the volume of oxygen gas produced and time for each of the two experiments?

1. A A
2. B B
3. C C
4. D D

Which of the following shows the effect of adding a catalyst to a system in a state of dynamic equilibrium?
(the rate of the forward reaction increases by the same amount as the rate of the reverse reaction / no change happens in the concentration of any of the reactants or products / the value of Kc of the reaction increases)

1. A ✓ / ✓ / ✓
2. B ✓ / ✓ / ✗
3. C ✗ / ✓ / ✓
4. D ✓ / ✗ / ✗

The reaction of iron with steam in a closed vessel is a reversible reaction.
Which of the following leads to a change in the mass of iron in the equilibrium reaction?
(adding steam / increasing the pressure / adding a catalyst)

1. A ✓ / ✗ / ✓
2. B ✗ / ✓ / ✗
3. C ✓ / ✗ / ✗
4. D ✗ / ✓ / ✓

The following two equations represent one reaction under different conditions:
(1) A + B →(Δ , cat) 2D
(2) A + B →(Δ) 2D
Which of the following describes reaction (2) compared with reaction (1)?

1. A It takes place at a lower temperature and its activation energy is lower.
2. B It takes place at a higher temperature and its activation energy is lower.
3. C It takes place at a higher temperature and its activation energy is greater.
4. D It takes place at a lower temperature and its activation energy is greater.

The following terms represent the numbers (1) to (6) in the opposite chart «not in order»:
(enzymes / rate of reaction / catalyst / position of equilibrium / biological reactions / activation energy)
Which of the following represents correct data?

1. A (1) : catalyst , (2) : enzymes , (4) : position of equilibrium.
2. B (3) : biological reactions , (5) : position of equilibrium , (6) : activation energy.
3. C (1) : catalyst , (3) : biological reactions , (6) : position of equilibrium.
4. D (2) : enzymes , (4) : activation energy , (5) : rate of reaction.

The solid substance (A) dissolves in water forming a solution that reacts instantly with NaCl(aq) forming a white precipitate, and it also reacts with the solution of substance (B) forming substance (C), which is used in the gelatinous layer of photographic films.
Which of the following is correct?

1. A (A) : AgNO₃ , (B) : NaBr , (C) : AgBr
2. B (A) : AgCl , (B) : NaCl , (C) : AgCl
3. C (A) : AgNO₃ , (B) : NaBr , (C) : AgCl
4. D (A) : AgCl , (B) : NaBr , (C) : AgBr

The opposite table shows the results of two experiments:
Experiment (1) : initial concentration [NO₂] = 0.03 M , [N₂O₄] = 0.5 M , concentration at equilibrium [NO₂] = 0.0475 M , [N₂O₄] = 0.491 M
Experiment (2) : initial concentration [NO₂] = 0.04 M , [N₂O₄] = 0.6 M , concentration at equilibrium [NO₂] = 0.0523 M , [N₂O₄] = 0.594 M
(1) Write the equation of the chemical reaction taking place, including the value of Kc
(2) Were the two experiments (1) and (2) carried out at the same temperature? Explain.

The opposite graph shows the change in [X] when the temperature of the following reaction is lowered starting from time t₁ :
CaCO₃(s) ⇌ CaO(s) + CO₂(g)
(1) What is substance (X)? Explain.
(2) Is the reaction exothermic or endothermic? Explain.

Name three external factors that shift an exothermic gaseous equilibrium reaction in the direction of forming the reactants.

Calculate the partial pressure of each of CO₂(g) and H₂O(v) in the following equilibrium reaction:
2NaHCO₃(s) ⇌ Na₂CO₃(s) + CO₂(g) + H₂O(v) Kp = 2.6 × 10³

From the equilibrium reaction: PCl₃(g) + Cl₂(g) ⇌ PCl₅(g) ΔH = −124 kJ/mol
(1) Explain the effect of increasing the pressure on this reaction.
(2) Explain the effect of lowering the temperature on this reaction.

Ammonia gas is prepared in industry from its elements.
Suggest two different ways to increase the [NH₃] produced without adding more reactants.

The position of equilibrium of the following reaction changes when the concentration of the reactants changes: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
(1) Name two other factors that can affect the position of equilibrium of this reaction.
(2) How can you tell from the opposite graph that the reaction has reached the state of equilibrium?

In the opposite equilibrium reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
What is the effect of adding V₂O₅ on each of:
(1) the concentration of SO₃
(2) the value of Kc of the reaction.

The opposite figure shows the change in [CO] and [CH₄] with time in the reaction:
CH₄(g) + H₂O(v) ⇌ CO(g) + 3H₂(g) ΔH = +206 kJ/mol
Draw on the opposite graph a curve that shows the change in:
(1) [H₂] with time.
(2) [CO] only, when a suitable catalyst is used.

The opposite graph represents the forward reaction of a reversible reaction.
(1) Explain the change in the concentration of each of: (A) (A) when the temperature of the equilibrium reaction is raised. (B) (C) when the external pressure on the equilibrium reaction is increased.
(2) What is the effect of adding a catalyst to the reaction mixture on each of: (A) the activation energy of the reaction. (B) ΔH of the reaction.

What are the two factors that do not change the position of equilibrium of the following reversible reaction? Explain:
SO₂(g) + NO₂(g) ⇌ SO₃(g) + NO(g) + Energy

The opposite graph shows the volume of hydrogen gas given off from the reaction of zinc powder with excess hydrochloric acid:
(1) Why does the volume of gas stay constant 6 min after the start of the reaction?
(2) Draw on the same opposite graph a curve that shows the rate of reaction when the mixture of reactants is heated.

Explain the following in the light of the collision theory:
(1) A mixture of natural gas and air reacts at a high temperature, while an explosion happens in the same mixture at a lower temperature when a piece of platinum is added to it.
(2) A piece of coal does not react with oxygen at room temperature.

In the following equilibrium reaction: C(s) + CO₂(g) ⇌ 2CO(g)
If the total pressure of this system at equilibrium is 40 atm and the partial pressure of carbon monoxide gas is 31.6 atm, then the value of Kp for this system equals ..........

1. A 8.487
2. B 3.760
3. C 118.87
4. D 131.98

From the following equilibrium reaction: 2X₂(g) + Y₂(g) ⇌ 2X₂Y(g) − Heat
Which of the following is correct regarding its effect on this reaction?

1. A Adding X₂ increases the concentration of the products and increases the amount of energy released.
2. B Adding Y₂ increases the concentration of the products and increases the amount of energy absorbed.
3. C Removing heat from the reaction space increases the value of the equilibrium constant.
4. D Increasing the heat in the reaction space decreases the value of the equilibrium constant.

Which of the following reactions is the fastest?

1. A A magnesium strip of mass 10 g with 25 mL of 0.2 M H₂SO₄ at room temperature.
2. B A magnesium strip of mass 5 g with 50 mL of 0.1 M H₂SO₄ at 35°C
3. C Magnesium powder of mass 10 g with 50 mL of 0.1 M H₂SO₄ at room temperature.
4. D Magnesium powder of mass 5 g with 25 mL of 0.2 M H₂SO₄ at 35°C

Study the two tubes (A , B) in the shown figure:
Which of the following describes the result of the reaction in each of the two tubes?

1. A The rate of disappearance of the zinc piece in tube (A) is greater than its rate of disappearance in (B).
2. B The rate of disappearance of the zinc piece in tube (B) is greater than its rate of disappearance in (A).
3. C The amount of hydrogen gas produced in (B) is greater than in (A) when the zinc dissolves completely.
4. D The amount of hydrogen gas produced in (B) is less than in (A) when the zinc dissolves completely.

Which of the following expresses the effect of heat on a system in a state of equilibrium?

1. A Lowering the temperature decreases the value of Kc in exothermic reactions.
2. B Raising the temperature increases the value of Kc in exothermic reactions.
3. C Lowering the temperature decreases the value of Kc in endothermic reactions.
4. D Raising the temperature decreases the value of Kc in endothermic reactions.

In the following equilibrium system: 2H₂O(l) ⇌ 2H₂(g) + O₂(g) , ΔH = +286 kJ
Which of the following choices is correct when the temperature is lowered?

1. A The value of the equilibrium constant Kc increases and the rate of dissociation of water decreases.
2. B The value of the equilibrium constant Kc increases and the rate of formation of water decreases.
3. C The value of the equilibrium constant Kc decreases and the rate of dissociation of water decreases.
4. D The value of the equilibrium constant Kc decreases and the rate of formation of water decreases.

The following reaction is in a state of equilibrium at a certain temperature: 2HI(g) ⇌ H₂(g) + I₂(g)
If the total pressure at equilibrium = 2 atm, and the partial pressure of each of H₂ and I₂ is: (P_H₂ = P_I₂ = 0.4 atm)
Which of the following represents the value of Kp when the volume of the vessel is halved?

1. A 0.05
2. B 0.11
3. C 0.25
4. D 0.40

In the following equilibrium reaction: 2NO₂(g) ⇌ N₂(g) + 2O₂(g)
the total pressure at equilibrium is 3.2 atm, the partial pressure of NO₂ gas is 2 atm and the partial pressure of O₂ gas is 1 atm
Which of the following expresses the value of Kp for the reaction?

1. A 0.1
2. B 0.2
3. C 0.05
4. D 5

Which of the following expresses one of the reasons for using nickel as a catalyst in the hydrogenation of oils?

1. A It increases the surface area of the reactants.
2. B It decreases the chances of collision between the molecules of the reactants.
3. C The 4s and 3d electrons take part in increasing the concentration of the reactants on its surface.
4. D It increases the activation energy of the molecules of the reactants.

Which of the following does not express a reversible reaction?

1. A Preparing ammonia gas from its elements in a closed vessel.
2. B Adding acetic acid to ethyl alcohol.
3. C Adding magnesium sulphate solution to sodium carbonate solution.
4. D Adding iron(III) chloride solution to ammonium thiocyanate solution.

In which of the following equilibrium reactions is the equilibrium activated in the forward direction when the volume of the reaction vessel is increased?

1. A N₂O₄(g) ⇌ 2NO₂(g)
2. B H₂(g) + I₂(g) ⇌ 2HI(g)
3. C 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
4. D N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

Two tubes (A , B) each contain equal masses of an active metal and the same acid. The reaction in tube (B) ended in less time than in (A).
Which of the following is a reason for the difference in the time of the two reactions?

1. A Dividing the metal into small pieces in tube (A).
2. B Adding a catalyst to tube (A).
3. C Raising the temperature of tube (B).
4. D Adding water to tube (B).

Ammonia is prepared in industry by the Haber-Bosch reaction, according to the equation: N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
Which of the following figures expresses the effect of increasing the partial pressure of nitrogen gas on the previous equilibrium?

1. A A
2. B B
3. C C
4. D D

According to the following equilibrium reaction: COCl₂(g) ⇌ CO(g) + Cl₂(g)
When an amount of COCl₂(g) is placed in a closed vessel of volume 1 L, at equilibrium the pressure of Cl₂(g) equals 0.3 atm and the total pressure at equilibrium equals 0.8 atm
then the value of Kp equals ..........

1. A 0.3
2. B 2.22
3. C 0.45
4. D 1.5

The following equation expresses a hypothetical reaction in a closed vessel at the state of equilibrium: A(s) + B(l) ⇌ C(g) + D(g) , ΔH = 84.3 kJ
Which of the following factors decreases the number of moles of substance (C)?

1. A Adding a little of substance (A) to the reaction medium.
2. B Removing a little of substance (D) from the reaction medium.
3. C Decreasing the volume of the vessel.
4. D Increasing the temperature.

Which of the following graphs expresses the effect of a catalyst on a reaction in a state of equilibrium?

1. A A
2. B B
3. C C
4. D D

When 0.2 mol of hydrazine gas is placed in a closed vessel of volume one litre, the equilibrium expressed by the following equation took place: N₂H₄(g) ⇌ N₂(g) + 2H₂(g) , ΔH < 0
At equilibrium, the concentration of hydrogen gas was [H₂] = 0.2 M. When the temperature of the system is raised and the state of equilibrium is reached again, the concentration of nitrogen gas [N₂] becomes ..........

1. A 0.08 M
2. B 0.20 M
3. C 0.30 M
4. D 0.10 M

The following equilibrium reaction is in a closed vessel: ICl(g) + Cl₂(g) ⇌ ICl₃(g) (ICl : dark brown , ICl₃ : yellow)
When the vessel is placed in a basin of hot water, the colour of the mixture becomes dark brown.
Which of the following expresses the type of the reaction (exothermic or endothermic) and the change that leads to decreasing the intensity of the brown colour?

1. A Exothermic – decreasing the pressure.
2. B Endothermic – increasing the pressure.
3. C Exothermic – decreasing the volume of the vessel.
4. D Endothermic – increasing the volume of the vessel.

When light falls on a sensitive photographic film,
which of the following describes the chemical change taking place?

1. A Silver ions gain electrons from bromide ions.
2. B Bromide ions gain electrons from silver ions.
3. C Silver is oxidized to silver ions.
4. D Bromide ions are reduced to bromine.

In the following equilibrium reaction: 2NO₂(g) ⇌ N₂O₄(g) , Kp = 6.15
At equilibrium, the partial pressure of (NO₂) gas in the vessel was (0.15 atm), so the value of the partial pressure of (N₂O₄) gas equals ..........

1. A 0.0225 atm
2. B 0.1383 atm
3. C 0.2767 atm
4. D 0.9225 atm

The opposite figure shows the energy diagram of a reversible reaction at equilibrium:
Which of the following graphs expresses the relation between Kc and temperature for this reaction?

1. A A
2. B B
3. C C
4. D D

When equal masses of zinc react with excess hydrochloric acid,
which of the following choices expresses the reaction that produces the same volume of hydrogen gas in the least possible time (given that the masses of zinc are equal)?

1. A A zinc strip with an acid of concentration 0.1 M at 25°C
2. B Zinc powder with an acid of concentration 1 M at 50°C
3. C Zinc powder with an acid of concentration 0.1 M at 25°C
4. D A piece of zinc with an acid of concentration 1 M at 50°C

The following equilibrium reaction is in a closed vessel: 2A₂X(g) + XY₂(g) ⇌ 3X(s) + 2A₂Y(g) , ΔH < 0 (X(s) : yellow in colour)
Which of the following is correct?

1. A Adding more of substance (X) shifts the equilibrium in the reverse direction.
2. B When the vessel is placed in a cooling mixture, the partial pressure of XY₂ gas increases
3. C The mass of the precipitate increases as the pressure increases.
4. D The volume of A₂Y decreases when the volume of the vessel is decreased.

In the opposite equilibrium reaction: Heat + 2AB(g) ⇌ A₂(g) + B₂(g) , (Kc = 80)
If you know that: [A₂] = 2 M , [B₂] = 2 M
Which of the following represents the possible [AB] when the temperature is raised?

1. A 0.500 M
2. B 0.100 M
3. C 0.223 M
4. D 0.300 M

In the opposite equilibrium reaction: A₂(g) + 3B₂(g) ⇌ 2AB₃(g) , ΔH < 0
Which of the following changes increases the rate of the reverse reaction?

1. A Lowering the pressure with cooling.
2. B Lowering the pressure with heating.
3. C Using a catalyst with cooling.
4. D Decreasing the volume of the vessel with heating.

In the opposite equilibrium reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
Which of the following expresses the role of vanadium pentoxide as a catalyst for this reaction?

1. A It increases the number of molecules that react on collision.
2. B It increases the activation energy of the reactants.
3. C It decreases the concentration of the products only.
4. D It increases the rate of decomposition of SO₃ only.

N₂H₄(g) ⇌ N₂(g) + 2H₂(g) , ΔH = (+)
Which of the following choices is correct when the volume of the vessel is decreased?

1. A The partial pressure of hydrazine decreases.
2. B The partial pressure of hydrogen gas increases.
3. C The value of the equilibrium constant increases.
4. D The rate of dissociation of hydrazine decreases.

In the opposite reaction: Cu(s) + 4HNO₃(l) →(conc , Δ) Cu(NO₃)₂(aq) + 2H₂O(l) + 2NO₂(g)
Which of the following choices decreases the rate of the reaction?

1. A Increasing the temperature.
2. B Increasing the surface area of the reactants.
3. C Adding water to the reaction medium.
4. D Adding drops of Cu(NO₃)₂ solution

In the opposite reaction: Zn(s) + 2HCl(aq) →(dil.) ZnCl₂(aq) + H₂(g)
The amount of hydrogen gas produced from the previous reaction per unit time can be increased by ..........

1. A placing the vessel in a cooling mixture.
2. B adding a little water to the reaction medium.
3. C increasing the volume of the vessel.
4. D increasing the number of moles of HCl per unit volume.

In the opposite reaction: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
Which of the following factors increases the rate of the reaction?

1. A Grinding the magnesium.
2. B Decreasing the concentration of HCl(aq)
3. C Cooling.
4. D Increasing the volume of the reaction vessel.

When an active metal (X) reacts with a strong mineral acid (Y),
what modification can be made so that this reaction takes place in less time?

1. A Dividing the metal into small pieces.
2. B Decreasing the volume of the acid.
3. C Lowering the temperature of the reaction.
4. D Increasing the pressure.

In the opposite equilibrium reaction: A₂(g) + B₂(g) ⇌ 2AB(g)
If the rate of formation of AB gas (at 25°C) equals (3 L/sec), when the temperature of the reaction is raised to (45°C), the rate of formation of AB gas equals ..........

1. A 12 L/sec
2. B 6 L/sec
3. C 5.4 L/sec
4. D 9 L/sec

In the opposite reaction: ½N₂(g) + ½O₂(g) + E ⇌ NO(g)
The rate of decomposition of nitric oxide can be increased by ..........

1. A removing nitrogen, and raising the temperature.
2. B adding oxygen, and increasing the pressure.
3. C removing nitrogen, and lowering the temperature.
4. D adding oxygen, and lowering the pressure.

In the opposite reaction: H₂(g) + I₂(g) ⇌ 2HI(g) − Heat
the value of Kc increases when ..........

1. A the temperature is lowered.
2. B the concentration of H₂ gas is increased
3. C the concentration of H₂ gas is decreased
4. D the temperature is increased.

In the equilibrium reaction: 2NO₂(g) ⇌ N₂O₄(g) + Heat
the value of the equilibrium constant of this reaction changes with the change of ..........

1. A pressure and the catalyst.
2. B temperature only.
3. C concentration and the catalyst.
4. D pressure only.

In the reaction: H₂N – NH₂(g) ⇌ N₂(g) + 2H₂(g) , ΔH = (−)
the amount of hydrogen given off can be increased by ..........

1. A increasing the temperature.
2. B increasing the volume of the vessel.
3. C adding more N₂ to the reaction medium.
4. D adding a catalyst to the reaction medium.

In the equilibrium reaction: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) , ΔH = −92 kJ
the reaction shifts in the direction of forming ammonia gas when ..........

1. A more nitrogen gas is added and the temperature is lowered.
2. B nitrogen gas is removed and the pressure is increased.
3. C more hydrogen gas is added and the temperature is raised.
4. D hydrogen gas is removed and the pressure is decreased.

In the following equilibrium reaction: A₂(g) + 3B₂(g) ⇌ 2AB₃(g) , ΔH < 0
Which of the following factors leads to an increase in the rate of the forward reaction?

1. A Increasing the pressure and cooling.
2. B Increasing the pressure and the heat.
3. C Using a catalyst and cooling.
4. D Using a catalyst and increasing the volume of the vessel.

If the value of the equilibrium constant of the reaction: H₂(g) + Cl₂(g) ⇌ 2HCl(g) is Kc = 4.4 × 10³²
then the value of Kc of the reaction: ½H₂(g) + ½Cl₂(g) ⇌ HCl(g) equals ..........

1. A 2.2 × 10³²
2. B 4.4 × 10³²
3. C 2.1 × 10¹⁶
4. D 1.1 × 10¹⁶

In the opposite equilibrium reaction: N₂H₄(g) ⇌ N₂(g) + 2H₂(g) + Heat , Kc = 0.04
If you know that: [N₂H₄] = 0.1 M , [H₂] = 0.2 M
then [N₂] when the temperature is raised equals ..........

1. A 0.08 M
2. B 0.2 M
3. C 0.3 M
4. D 0.1 M

The following relation is used to calculate Kp for a reaction: Kp = 1 / ([X₂]² [Y₂])
Which of the following equations expresses this reaction?

1. A 2X₂(l) + Y₂(g) ⇌ 2X₂Y(g)
2. B 2X₂(g) + Y₂(g) ⇌ 2X₂Y(l)
3. C 2X₂(g) + Y₂(s) ⇌ 2X₂Y(aq)
4. D 2X₂(g) + Y₂(s) ⇌ 2X₂Y(l)

In the opposite reaction: CO(g) + Cl₂(g) ⇌ COCl₂(g)
An amount of CO(g) and Cl₂(g) was placed in a flask, and at the state of equilibrium the pressure inside the flask was (1.2 atm). If you know that the partial pressures of the three gases are equal, then Kp equals ..........

1. A 1
2. B 2.5
3. C 0.4
4. D 0.16

In the opposite equilibrium reaction: Br₂(g) + H₂(g) ⇌ 2HBr(g)
If the partial pressures of bromine, hydrogen and hydrogen bromide gases are 0.5 atm , 1 atm and 1.5 atm respectively,
then the equilibrium constant of the dissociation of hydrogen bromide into its elements equals ..........

1. A 2.2
2. B 0.22
3. C 0.45
4. D 4.5

In the opposite reaction: A(g) ⇌ 2B(g)
When the partial pressures at equilibrium are as follows: A = 0.213 atm , B = 0.213 atm
then the value of the equilibrium constant of the reaction equals ..........

1. A 0.213
2. B 4.69
3. C 0.426
4. D 0.1065

In the opposite equilibrium reaction: 2NO₂(g) ⇌ N₂O₄(g) , (Kp = 20)
then the value of Kp for the dissociation of 2 mol of N₂O₄ equals ..........

1. A 40
2. B 25 × 10⁻³
3. C 2.5 × 10⁻³
4. D 400

In the opposite reaction: PCl₃(g) + Cl₂(g) ⇌ PCl₅(g) , (Kp₁ = 0.013)
then the value of Kp₂ of the reaction: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) equals ..........

1. A 76.92
2. B 67.29
3. C 61.79
4. D 82.6

In the opposite reaction: 2H₂O(l) + O₂(g) ⇌ 2H₂O₂(l) , (Kp = 0.2)
then the value of the partial pressure of oxygen equals ..........

1. A 0.2 atm
2. B 0.02 atm
3. C 5 atm
4. D 0.5 atm

From the opposite reaction: 4NH₃(g) + 3O₂(g) ⇌ 2N₂(g) + 6H₂O(v) , (Kp = 15.47)
If the partial pressures are: ammonia 1.5 atm , oxygen 1.16 atm , water vapour 2.4 atm
then the partial pressure of nitrogen equals ..........

1. A 2.4 atm
2. B 1.6 atm
3. C 0.8 atm
4. D 0.64 atm