CHEMICAL REACTIONS, STOICHIOMETRY, REACTION RATES and CHEMICAL EQUILIBRIUM

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Concerning the reaction:

4NH₃(g) + 3O₂(g) => 2N₂(g) + 6H₂O(g)

∆H = -1267 kJ

Three changes can be made to the reaction:

I adding a catalyst
II heating the mixture
III increasing the pressure

Which of the changes will increase the yield of the forward reaction?
1. none of the above
2. II only
3. III only
4. I only
Which one of the following is a reaction of aluminium hydroxide?
1. It reacts with sodium hydroxide solution to give a solution containing tetrahydroxoaluminate ion, Al(OH)₄^-.
2. It reacts with dilute sulfuric acid to give a white precipitate of aluminium sulfate
3. It reacts with dilute hydrochloric acid to give a white precipitate of aluminium chloride
4. It fumes in the presence of hydrochloric acid because volatile aluminium chloride is produced
Which set of the following 0.1 mol L^-1 solutions when mixed will produce only a white precipitate?
1. Barium nitrate Sodium hydroxide Potassium chloride Copper nitrate
2. Zinc nitrate Copper sulfate Barium chloride Sodium carbonate
3. Zinc nitrate Potassium chloride Sodium nitrate Aluminium nitrate
4. Barium chloride Sodium nitrate Potassium chloride Aluminium sulfate
Which of the following fertilisers has the greatest percentage of nitrogen by mass?
1. (NH₄)₂CO₃
2. (NH₄)₂SO₄
3. NH₂CONH₂
4. NH₄NO₃
When silver sulfide is added to water, the following equilibrium is esatblished.

Ag₂S(s) <=> 2 Ag⁺ (aq) + S^2- (aq)

The value of the equilibrium constant for this reaction is very small. What does this suggest?
1. Silver sulphide reacts extensively with water
2. This reaction is endothermic
3. Adding more silver sulphide will increase the amount of ions in solution
4. Silver sulfide has a very low solubility
Group I and II metal hydrides react with water according to the following equation:

H^- + H₂O(l) => OH^- (aq) + H₂(g)

In a particular experiment, 1.00g of each of the following metal hydrides is treated with an excess of water. Which metal hydride will produce the greatest volume of hydrogen?
1. KH
2. MgH₂
3. CaH₂
4. NaH
The following equilbrium is used in the production of alumina via the Bayer Process.

Al(OH)₃(s) + OH^-(aq) <=> Al(OH)₄^-(aq)

Which one of the following will move hte equilibrium in the forward direction to produce more aluminate ion Al(OH)₄^-(aq) ?
1. addition of caustic soda (sodium hydroxide)
2. addition of Al(OH)₃(s) seed crystal
3. passing a large electric current through the solution using carbon electrodes
4. addition of cryolite
Which of the following best explains the way in which a catalyst increases the rate of a reaction?
1. A catalyst provides an alternative reaction pathway with a lower heat of reaction : hence less energy is needed for the partucles to react
2. A catalyst provides an alternative reaction pathway with a lower activation energy: hence a greater fraction of collisions is effective
3. A catalyst provides additional energy to the particles: hence a greater fraction of collisions is effective
4. A catalyst increases the rate of the forward reaction but not the reverse reaction: hence the overall rate is increased
For an exothermic reaction, which one of the following statements is true?
1. The reverse reaction is also exothermic
2. The potential energy of the products is greater than that of the reactants
3. The reverse reaction has a higher activation energy than the forward reaction
4. The trnsition state for the reverse reaction has higher potential energy than that for the froward reaction
Zincate ions react with hydrochloric acid as follows.

Zn(OH)₄^2-(aq) + 2H⁺(aq) => Zn(OH)₂(s) + 2H₂O (l)

Which one of the following statements is correct?
1. Zn(OH)₄^2-(aq) acts as an acid
2. Zn(OH)₄^2-(aq) is reduced
3. Zn(OH)₄^2-(aq) forms a complex ion
4. Zn(OH)₄^2-(aq) acts as a base
Concerning the reaction:

4NH₃(g) + 3O₂(g) => 2N₂(g) + 6H₂O(g)

∆H = -1267 kJ

Three changes can be made to the reaction:

I adding a catalyst
II heating the mixture
III increasing the pressure

Which one of the options represents the equilibrium constant for the reaction?
1. K = ([NH₃]⁴[O₂]³)/([N₂]²[H₂O]⁶)
2. K = ([N₂]²[H₂O]⁶)/([NH₃]⁴[O₂]³)
3. K = ([NH₃]⁴ + [O₂]³)/([N₂]² + [H₂O]⁶)
4. K = ([N₂]²/([NH₃]⁴[O₂]³)
Concerning the reaction:

4NH₃(g) + 3O₂(g) => 2N₂(g) + 6H₂O(g)

∆H = -1267 kJ

Three changes can be made to the reaction:

I adding a catalyst
II heating the mixture
III increasing the pressure

Which of the changes will increase the rate of the forward reaction?
1. I and III only
2. I, II and III
3. I and II only
4. I only
Which one of the following statements about the transition state (also called the activated complex) in a chemical reaction is false?
1. Transition state formation involves bond making
2. It has lower energy than the products of the reaction
3. It is unstable and has a very short lifetime
4. It has higher energy than the reactants
Concerning the reaction:

2HI(g) <=> H₂(g) + I₂(g)

In the absence of a catalyst, the activation energy for the forward reaction is 183 kJ mol^-1 and the activation energy for the reverse reaction is 157 kJ mol^-1. In the presence of a platimum catalyst the activation energy for the forward reacation is 58 kJ mol^-1.

What is the ΔH for the reaction, 2HI(g) <=> H₂(g) + I₂(g), in the presence of a platinum catalyst?
1. -84 kJ mol^-1
2. +26 kJ mol^-1
3. -26 kJ mol^-1
4. +84 kJ mol^-1
When CoCl₂ is dissolved in dilute hydrochloric acid, the following equilibrium is established.

RED Co(H₂O)₆²⁺ (aq) + 4 Cl^- (aq) <=> DEEP BLUE CoCl₄^2- (aq) + 6H²O(l)

The solution appears purple in colour as a result of the mixture of the blue and red colours. Which one of the following changes will cause the solution to become more blue in colour?
1. The solution is diluted by the addition of water
2. A few drops of concentrated HCl is added
3. A catalyst is added
4. A few millimetres of AgNO₃ solution is added
If solid calcium carbonate is heated in a sealed container, the following equilibrium is established.

CaCO₃(s) <=> CaO(s) + CO₂(g)

∆H=+178 kJ/mol

For this system, which one of the following statements about the equilibrium constant K is correct?
1. K will increase if the pressure of the system is decreased
2. K will increase if the temperature of the system is increased
3. K will decrease if the partial pressure of the CO₂ is reduced
4. K will remain constant, regardless of any changes made to the system
Which one of the following pairs of substances will react together when mixed ?
1. Ni²⁺ + Zn
2. Cl₂ + Cu²⁺
3. Zn + Cl^-
4. Ni²⁺ + Cu
5.0 mL of CH₄, 5.0 mL of C₂H₄, and 25.0 mL of O₂ are mixed. All three gas volumes are measured at 25^oC and 1.00 atm. The mixture is ignited. What volume of O₂ (at 25^oC and 1.00 atm) is consumed in the combustion?
1. 25.0 mL
2. 10.0 mL
3. 20.0 mL
4. 15.0 mL
Concerning the reaction:

2HI(g) <=> H₂(g) + I₂(g)

In the absence of a catalyst, the activation energy for the forward reaction is 183 kJ mol^-1 and the activation energy for the reverse reaction is 157 kJ mol^-1. In the presence of a platimum catalyst the activation energy for the forward reacation is 58 kJ mol^-1.

What one of the following statements about the reaction, H₂(g) + I₂(g) <=> 2HI(g) , in the presence of a platinum catalyst is true?
1. The activation energy cannot be known without further experiment.
2. The activation energy is 157 kJ mol^-1
3. The activation energy is 32 kJ mol^-1
4. The activation energy is 99 kJ mol^-1
Consider the following endothermic reaction for the production of hydrogen gas in a rigid container:

CH₄(g) + H₂O(g) <=> CO(g) + 3H₂(g)

Which of the following would increase the final yield of hydrogen gas?
1. increasing the pressure
2. adding a catalyst
3. increasing the temperature
4. adding inert argon gas
What is the equilibrium constant expression for the dissolving of lead(II) chloride according to the following equation?

PbCl₂(s) <=> Pb²⁺ (aq) + 2 Cl^-(aq)
1. K= [Pb²⁺][2Cl^-]
2. K= [PbCl₂] divide by [Pb²⁺][Cl^-]²
3. K= [Pb²⁺][Cl^-]²
4. K= [Pb²⁺][Cl^-]² divide by [PbCl₂]
Which one of the following mixtures of salts will dissolve in water to produce a clear, colourless solution?
1. calcium nitrate, potassium bromide, sodium chloride
2. cadmium sulfate, potassium chloride, sodium carbonate
3. calcium nitrate, potassium carbonate, sodium chloride
4. calcium nitrate, nickel sulfate, potassium carbonate
The solvent acetone (propanone) an be made by ehating 2-propanol with a copper catalyst. the reaction, which is endothermic, is represented by the following equation.

CH₃CH(OH)CH₃ (g) <=> CH₃C(O)CH₃(g) + H₂(g)

What happens if the temperature of the system is increased from 300^oC to 400^oC ?
1. The yield of acetone increases
2. The yield of acetone is unchanged because the forward and reverse reactions are both accelearted.
3. The yield of acetone decreases
4. The yield of hydrogen decreases
Which one of the following will change the value of the equilibrium constant (K) for a reaction?
1. increasing the pressure
2. nothing, since it is a constant
3. increasing the state of subdivision of the reactants
4. increasing the temperature
A saturated solution of PbCl2 is in contact with excess undissolved solid.

PbCl2(s) <=> Pb²⁺(aq) + 2Cl^-(aq)

A small quantity of KCl(s) is stirred into the solution. What would happen to the mixture?

I The concentration of Cl^-(aq) increases
II The concentration of Pb²⁺(aq) decreases
III The mass of PbCl₂(s) increases
IV The KCl(s) will not dissolve in this solution
1. IV only
2. I and II only
3. I only
4. I, II and III only
Which one of the following reagents, when mixed with ammonium sulfate and heated, produces ammonia?
1. dilute hydrochloric acid
2. a solution containing potassium permanganate and dilute sulfuric acid
3. water
4. limewater (saturated calcium hydroxide solution)
Concerning this reaction:

CaCO₃(s) <=> CaO(s) + CO₂(g)

∆H = 178.3 kJ mol-1

Which one of the following is the equilibrium constant expression for this reaction?
1. K = [CO₂]
2. K=([CaO][CO₂])/[CaCO₃]
3. K=([CaO]+[CO₂])/[CaCO₃]
4. K=1/[CO₂]
Concerning this reaction:

CaCO₃(s) <=> CaO(s) + CO₂(g)

∆H = 178.3 kJ mol-1

Consider a sealed system in which CaCO₃, CaO and CO₂ are at equilibrium.

Now consider the following actions:

I Add more CO₂(g) to the system

II Add more CaCO₃(s) to the system

III Decrease the volume of the system

IV Increase the temperature of the system

One or more of these actions lead to a change in CO₂(g) concentration (after equilibrium is re-established).

Which statement below is true?
1. All actions lead to a change in CO₂(g) concentration
2. Only III and IV lead to a change in CO₂(g) concentration
3. Only II, III and IV lead to a change in CO₂(g) concentration
4. Only IV leads to a change in CO₂(g) concentration
1.0 mol of an unknown metal reacts with excess hydrochloric acid to produce 1.5 mol of hydrogen gas. What is the charge on the metal ion?
1. +3
2. +1
3. +2
4. +4
Consider the following reaction at equilibrium.

2 NO (g) + O₂ (g) <=> 2 NO₂ (g)

ΔH = -114 kJ

Which one of the following changes will increase the concentration of NO₂(g) in the mixture when equilibrium is re-established?
1. decreasing the concentration of NO at constant temperature and pressure
2. decreasing the concentration of O₂ at constant temperature and pressure
3. decreasing the pressure
4. decreasing the temperature
Consider the following potential energy diagram for a chemical reaction.

Which one of the following statements about this reaction is incorrect?
1. The ∆H for the reverse reaction is -Y
2. The reaction mixture will become hotter as the reaction proceeds
3. The activation energy for the reverse reaction is X-Y
4. The forward reaction rate is likely to be slower than the reverse reaction rate
Concerning the reaction:

2HI(g) <=> H₂(g) + I₂(g)

In the absence of a catalyst, the activation energy for the forward reaction is 183 kJ mol^-1 and the activation energy for the reverse reaction is 157 kJ mol^-1. In the presence of a platimum catalyst the activation energy for the forward reacation is 58 kJ mol^-1.

What is the ΔH for the reaction, 2HI(g) <=> H₂(g) + I₂(g), in the absence of a catalyst?
1. +26 kJ mol^-1
2. +84 kJ mol^-1
3. -84 kJ mol^-1
4. -26 kJ mol^-1
Which one of the following statements about the transition state in a chemical reaction is false?
1. The transition state is the highest energy state in the reaction
2. The transition state will be the same for a reaction whether a catalyst is used or not
3. The transition state is unstable and will only exist for a short period of time
4. The transition state corresponds to a point where bond breaking and bond forming is occuring
Which one of the following statements about the value of an equilibrium constant is false?
1. It indicates how quickly the reaction is likely to proceed
2. The value is independent on any catalysts present
3. The value is dependent on the temperature
4. It indicates the relative proportions of products to reactants at equilibrium
Which one of the following processes is exothermic?
1. I₂(g) => 2 I(g)
2. I₂(s) => I₂(g)
3. Na(g) => Na⁺(g) + e^-
4. Na⁺(g) + I^-(g) => NaI(s)

CHEMICAL REACTIONS, STOICHIOMETRY, REACTION RATES and CHEMICAL EQUILIBRIUM

Multiple Choice Quiz on Chemical Reactions, Stoichiometry, Reaction Rates and Chemical Equilibrium