Rate of Chemical Reaction questions

When an amount of water is heated in a closed vessel until the saturated vapour pressure is reached:
All of the following are correct, except ..........

1. A Physical equilibrium takes place.
2. B Continued heating at the same temperature increases evaporation.
3. C The number of water molecules that evaporate = the number of vapour molecules that condense.
4. D The vapour pressure becomes equal to the saturated water vapour pressure.

Which of the following equations represents a physical equilibrium process?

1. A H₂(g) + Cl₂(g) = 2HCl(g)
2. B 2SO₂(g) + O₂(g) = 2SO₃(g)
3. C 3O₂(g) = 2O₃(g)
4. D N₂(l) = N₂(g)

Which of the following reactions proceeds in both the forward and the reverse directions?

1. A Fe(s) + 2HCl(aq) = FeCl₂(aq) + H₂(g)
2. B BaCl₂(aq) + K₂SO₄(aq) = 2KCl(aq) + BaSO₄(s)
3. C CO(g) + H₂O(v) = CO₂(g) + H₂(g) (in a closed vessel)
4. D 2Cu(NO₃)₂(s) = 2CuO(s) + 4NO₂(g) + O₂(g)

Which of the following reactions reaches a state of equilibrium some time after the reaction starts?

1. A KCl(aq) + AgNO₃(aq) = KNO₃(aq) + AgCl(s)
2. B CH₃COOC₂H₅(l) + H₂O(l) = C₂H₅OH(aq) + CH₃COOH(aq)
3. C K₂SO₄(aq) + (CH₃COO)₂Pb(aq) = 2CH₃COOK(aq) + PbSO₄(s)
4. D Zn(s) + 2HCl(aq) = ZnCl₂(aq) + H₂(g)

Between which pairs of substances does a complete reaction take place?

1. A (CH₃COOH + C₂H₅OH) , (2Ag⁺ + SO₃²⁻).
2. B (2H⁺ + Mg) , (2Ag⁺ + SO₃²⁻).
3. C (CH₃COOC₂H₅ + H₂O) , (Na₂S₂O₃ + HCl).
4. D (CH₃COOC₂H₅ + H₂O) , (2H⁺ + Mg).

The reaction of lead(II) nitrate solution with potassium chloride solution is ..........

1. A complete and slow.
2. B incomplete and instantaneous.
3. C complete and instantaneous.
4. D incomplete and slow.

From the opposite reaction: X₂(g) + Y₂(g) = 2XY(g) (closed vessel)
All of the following describe the state of chemical equilibrium, except ..........

1. A The reactants are not completely consumed.
2. B The rate of consumption of (X₂) is half the rate of formation of (XY).
3. C The rate of consumption of (Y₂) equals the rate of consumption of (X₂).
4. D The concentrations of (X₂ , Y₂ , XY) are always equal.

Which of the following describes the reaction of HNO₃(aq) with sodium thiosulphate?

1. A Complete, with the formation of a gas only.
2. B Complete, with the formation of a gas and a precipitate.
3. C Incomplete and slow.
4. D Incomplete and fast.

In the reaction represented by the equation: CaCO₃(s) + 2HCl(aq) → H₂O(l) + CO₂(g) + CaCl₂(aq)
What change happens to the concentration of the ions with time?

1. A [H⁺] : decreases , [Ca²⁺] : increases , [Cl⁻] : increases.
2. B [H⁺] : decreases , [Ca²⁺] : increases , [Cl⁻] : does not change.
3. C [H⁺] : decreases , [Ca²⁺] : does not change , [Cl⁻] : increases.
4. D [H⁺] : does not change , [Ca²⁺] : increases , [Cl⁻] : does not change.

The reaction of heating magnesium bicarbonate solution is ..........

1. A complete, with the formation of a precipitate only.
2. B complete, with the formation of a gas and a precipitate.
3. C incomplete, because no precipitate or gas forms.
4. D incomplete, and no chemical equilibrium takes place in it.

The rate of a chemical reaction depends on all of the following, except ..........

1. A the presence of a catalyst.
2. B the concentration of the reactants.
3. C the temperature of the reaction medium.
4. D the heat content of the reactants.

A reaction was carried out in an open flask between hydrochloric acid and a strip of magnesium.
Which of the following can be used to measure the rate of this reaction before and after it takes place?

1. A The volume of the acid.
2. B The colour of the gas produced.
3. C The concentration of chloride ions.
4. D The mass of the flask and its contents.

All of the following describe a system in a state of equilibrium, except that ..........

1. A the reaction is reversible.
2. B the amounts of the substances taking part in the reaction remain equal.
3. C the concentrations of the reactants and the products remain constant.
4. D the rate of the forward reaction equals the rate of the reverse reaction.

The opposite graph shows the change in the volume of hydrogen gas produced from the reaction of iron filings with excess dilute sulphuric acid.
Which of the following explains the part PQ of the curve?

1. A Iron is a metal of moderate chemical activity.
2. B The decrease in the concentration of the acid with time reduces the speed of the reaction.
3. C The hydrogen gas produced reduces the speed of the reaction.
4. D The water produced from the reaction dilutes the acid further, which increases the speed of the reaction.

The opposite graph:
represents the reaction ..........

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

All of the following always describe a reaction at equilibrium, except that ..........

1. A the concentration of the reactants always equals the concentration of the products.
2. B the rate of consumption of a substance equals the rate of its formation.
3. C all the reacting and produced substances are present in the reaction medium.
4. D the rate of the forward reaction equals the rate of the reverse reaction.

All of the following always describe a gaseous chemical reaction at equilibrium, except ..........

1. A It takes place in a closed vessel.
2. B It takes place at constant temperature and pressure.
3. C The rate of the forward reaction equals the rate of the reverse reaction.
4. D The reverse reaction stops after a while.

The following reaction is carried out in a closed vessel:
H₂O(v) + CO(g) ⇌ H₂(g) + CO₂(g)
For the reaction to reach the state of equilibrium, ..........

1. A the concentrations of both CO and CO₂ increase
2. B the concentrations of both CO and CO₂ decrease
3. C the concentration of CO increases and the concentration of CO₂ decreases
4. D the concentration of CO decreases and the concentration of CO₂ increases

A reversible reaction reaches the state of equilibrium 60 s after the reaction starts.
All of the following express the value of the rate of the forward reaction (r₁) compared with the value of the rate of the reverse reaction (r₂), except ..........

1. A (at 2 s) r₂ < r₁
2. B (at 30 s) r₂ > r₁
3. C (at 55 s) r₂ < r₁
4. D (at 65 s) r₂ = r₁

H₂O and CO react in a closed vessel at a high temperature according to the equation:
H₂O(v) + CO(g) ⇌ H₂(g) + CO₂(g)
Before reaching the equilibrium point ..........

1. A the rates of the forward and reverse reactions are equal.
2. B the rates of both the forward and reverse reactions increase.
3. C the rate of the forward reaction decreases and the rate of the reverse reaction increases.
4. D the rate of the forward reaction increases and the rate of the reverse reaction decreases.

The opposite figure represents the rate of preparing ammonia from its elements.
Which of the following is correct?

1. A [H₂] : (1) , [NH₃] : (2) , [N₂] : (3).
2. B [N₂] : (1) , [H₂] : (2) , [NH₃] : (3).
3. C [H₂] : (1) , [N₂] : (2) , [NH₃] : (3).
4. D [N₂] : (1) , [NH₃] : (2) , [H₂] : (3).

A chemical substance decomposes at 30°C forming 50 mL of oxygen gas, which took a time of 80 s
Which of the following represents the rate of formation of oxygen gas?

1. A 50 mL / 80 s
2. B 50 mL / 30°C
3. C 20 mL / 80 s
4. D 25 mL / 30°C

In the opposite reaction: 2N₂O₅(g) → 4NO₂(g) + O₂(g)
At a certain temperature the rate of decomposition of N₂O₅ was 2.5 × 10⁻⁶ mol/s
What is the rate of formation of NO₂?

1. A 1 × 10⁻⁶ mol/s
2. B 1.25 × 10⁻⁶ mol/s
3. C 2.5 × 10⁻⁶ mol/s
4. D 5 × 10⁻⁶ mol/s

When aluminium reacts with copper(II) chloride solution, 0.56 g of copper was observed to be produced in 1 min
[Cu = 63.5 , Al = 27]
What is the mass of aluminium consumed in 20 s?

1. A 0.053 g
2. B 0.12 g
3. C 0.16 g
4. D 0.37 g

In the equilibrium reaction: 2NO₂(g) ⇌ N₂O₄(g)
Which graph represents [NO₂] during the reaction until the state of equilibrium is reached?

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

The following equation represents the equilibrium reaction between (X) and (Y) to produce the compound (Z):
X + Y ⇌ Z
Which of the following represents the change in the rate of each of the forward reaction and the reverse reaction with time?

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

The opposite graph represents the concentrations of three gases in a reversible reaction that reaches the state of equilibrium.
Which reaction does this graph represent?

1. A 2NO₂(g) ⇌ N₂(g) + 2O₂(g)
2. B CO(g) + 3H₂(g) ⇌ CH₄(g) + H₂O(v)
3. C N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
4. D 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

The following two graphs represent the reaction: 2NO₂(g) ⇌ N₂O₄(g)
Which of the following is correct?

1. A (1) : concentration , (2) : NO₂ , (3) : rate of reaction.
2. B (1) : concentration , (2) : N₂O₄ , (3) : rate of reaction.
3. C (1) : rate of reaction , (2) : N₂O₄ , (3) : concentration.
4. D (1) : rate of reaction , (2) : NO₂ , (3) : concentration.

From the opposite figure:
What is the type of bonding in the reactants,
and how is the rate of this reaction classified?

1. A Covalent / slow.
2. B Covalent / fast.
3. C Ionic / slow.
4. D Ionic / fast.

Which of the following equations represents the reaction with the fastest rate?

1. A C(s) + O₂(g) → CO₂(g)
2. B 2H₂O₂(l) → 2H₂O(l) + O₂(g)
3. C 2Al(s) + 3CuCl₂(aq) → 2AlCl₃(aq) + 3Cu(s)
4. D FeCl₃(aq) + 3NaOH(aq) → 3NaCl(aq) + Fe(OH)₃(s)

The reaction of a known mass of zinc carbonate pieces with excess dilute hydrochloric acid took 5 minutes.
When the previous reaction is repeated after crushing the same mass of zinc carbonate pieces, the reaction is completed in ..........

1. A less time / because the zinc carbonate particles are larger.
2. B less time / because the surface area of zinc carbonate exposed to the reaction is larger.
3. C the same time / because the mass of zinc carbonate did not change.
4. D more time / because the number of zinc carbonate particles is larger while the concentration of the acid is constant.

A piece of iron needed a time of 270 s to react with 0.1 M HCl acid.
What is the rate of reaction of the same acid with the same mass of iron filings?

1. A 3.7 × 10⁻⁴ M/s
2. B 2.5 × 10⁻⁴ M/s
3. C 5.4 × 10⁻³ M/s
4. D 6.1 × 10⁻⁵ M/s

Which of the following graphs represents the relation between the surface area of the reactants and the reaction time?

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

When does equilibrium take place in a closed flask between:
(1) ice and liquid water (at 0°C)?
(2) liquid bromine and bromine vapour (at 20°C)?

Ammonia gas is prepared from its elements:
(1) Why does the percentage of ammonia gas produced not represent 100% of the reacting substances?
(2) What is the effect of bringing a dry red litmus paper near the gas produced? Explain.

Two experiments were carried out on the reaction of calcium carbonate with dilute hydrochloric acid under the same conditions of pressure and temperature:
• In experiment (1): 20 mL of dilute hydrochloric acid were added to excess calcium carbonate powder.
• In experiment (2): 20 mL of dilute hydrochloric acid were added to excess calcium carbonate pieces.
From the opposite graph, identify, with explanation, the symbol of the curve that represents:
(1) experiment (1).
(2) experiment (2).

The opposite graph represents the volume of carbon dioxide gas produced from the reaction of pieces of calcium carbonate of equal masses with hydrochloric acid. Medium pieces of calcium carbonate were used in the first experiment and small pieces in the second experiment:
(1) Which of the two curves (X) and (Y) represents the reaction of the small pieces with the acid? Explain.
(2) What is the time taken to consume all the medium-sized pieces of calcium carbonate?

From the following graphs:
Which of the following statements is correct?

1. A Graph (X) : Kc = 1 and the reverse direction is dominant.
2. B Graph (Y) : Kc = 1 and the forward direction is dominant.
3. C Graph (X) : Kc > 1 and the forward direction is dominant.
4. D Graph (Y) : Kc > 1 and the reverse direction is dominant.

Which of the following equations represents a process in which the rate of the forward reaction equals the rate of the reverse reaction?

1. A AgNO₃(aq) + NaCl(aq) = AgCl(s) + NaNO₃(aq)
2. B HCl(aq) + H₂O(l) = H₃O⁺(aq) + Cl⁻(aq)
3. C N₂(g) + 3H₂(g) = 2NH₃(g) (open vessel)
4. D CH₃COOH(aq) + H₂O(l) = H₃O⁺(aq) + CH₃COO⁻(aq)

Which of the following reactions represents a state of equilibrium in an open vessel?

1. A CaCO₃(s) = CaO(s) + CO₂(g)
2. B 2Cu(NO₃)₂(s) = 2CuO(s) + 4NO₂(g) + O₂(g)
3. C FeCl₃(aq) + 3NH₄SCN(aq) = Fe(SCN)₃(aq) + 3NH₄Cl(aq)
4. D Zn(s) + CuSO₄(aq) = ZnSO₄(aq) + Cu(s)

Which of the following graphs represents the relation between the concentrations of the products and the reactants when a piece of magnesium metal is placed in dilute sulphuric acid solution?

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

In the reaction: BaCl₂ + Na₂SO₄ = 2NaCl + BaSO₄
Which of the following graphs represents the relation between concentration (C) and time (t) in the previous reaction?

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

(A) : AgNO₃(aq) + NaBr(aq) = AgBr(s) + NaNO₃(aq)
(B) : 2NO(g) + O₂(g) = 2NO₂(g) (closed vessel)
(C) : CH₃COOH(l) + C₂H₅OH(l) = CH₃COOC₂H₅(aq) + H₂O(l)
(D) : N₂(g) + 3H₂(g) = 2NH₃(g) (closed vessel)
Which of the previous reactions is a complete reaction?

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

All of the following are reversible reactions, except ..........

1. A CO₂(g) + H₂(g) = CO(g) + H₂O(v) (closed vessel)
2. B CH₃COOH(l) + C₂H₅OH(l) = CH₃COOC₂H₅(aq) + H₂O(l)
3. C 2Na(s) + 2HCl(aq) = 2NaCl(aq) + H₂(g)
4. D 2NO₂(g) = N₂O₄(g) (closed vessel)

Which of the following statements describes a chemical reaction in a state of equilibrium?

1. A The speed of the forward reaction is always greater than the speed of the reverse reaction.
2. B The reaction is always static, not dynamic.
3. C The concentrations of the products and the reactants are always constant.
4. D The concentrations of the products and the reactants are always equal.

Which of the following represents the opposite chart?

1. A 2A + B ⇌ 2C + 4D
2. B A + 3C ⇌ 2B + 4D
3. C 2A + B → 2C + 4D
4. D A + 3C → 2B + 4D

Which of the following statements represents the two curves shown in the opposite graph?

1. A Sodium chloride solution + silver nitrate solution.
2. B Iron nails covered with oil.
3. C Iron nails covered with water.
4. D Magnesium pieces + dilute hydrochloric acid.

Which of the following reactions is the fastest?

1. A Mg(s) + 2HCl(aq) = MgCl₂(aq) + H₂(g) (a piece)
2. B FeSO₄(aq) + 2NaOH(aq) = Fe(OH)₂(s) + Na₂SO₄(aq)
3. C CH₃COOH(l) + CH₃OH(l) = CH₃COOCH₃(aq) + H₂O(l)
4. D Fe(s) + ³⁄₂ O₂(g) + 3H₂O(l) = 2Fe(OH)₃(s) (rusting of iron)