WorksheetsWorld's biggest Electrolytic Quiz (It's a shocker!)
Total questions: 90
Worksheet time: 45mins
What is the main purpose of electrolysis?
To convert chemical energy into electrical energy
To produce a spontaneous chemical reaction
To convert electrical energy into chemical potential energy
To recharge non-rechargeable batteries
What type of cells convert chemical energy to electrical energy?
Rechargeable cells
Electrolytic cells
Galvanic cells
Spontaneous cells
How does a rechargeable battery 'recharge'?
By converting electrical energy directly into kinetic energy
By using electrolysis to reverse the chemical reaction
By spontaneously generating electrical energy
By converting thermal energy into electrical energy
What is a potential danger when passing an electric current through a sodium chloride solution during electrolysis?
The reaction is too spontaneous to control
The products could be very dangerous
The sodium chloride solution becomes a rechargeable battery
The electrical energy is not converted efficiently
What is the main industrial application of electrolysis mentioned in the text?
Purification of water
Extraction of metals from their ores
Generation of electricity
Production of chlorine gas
Which of the following minerals is associated with copper as per Table 14.1.1?
Hematite, Fe2O3
Chalcopyrite, CuFeS2
Argentite, Ag2S
Galena, PbS
What is the role of the power source in an electrolytic cell?
It decreases the concentration of the solution.
It separates the anions and cations.
It supplies energy to push electrons to the cathode.
It converts mechanical energy into electrical energy.
Which statement correctly describes the electron flow in both galvanic and electrolytic cells?
Electrons flow from anode to cathode in both cell types.
Electrons flow from cathode to anode in both cell types.
Electrons flow from anode to cathode in galvanic cells and from cathode to anode in electrolytic cells.
Electrons flow from cathode to anode in galvanic cells and from anode to cathode in electrolytic cells.
Which of the following is not a correct pair of metal and its mineral form as per the provided table?
Copper - Malachite, Cu2(CO3)(OH)2
Iron - Hematite, Fe2O3
Zinc - Sphalerite, Zn(FeS)
Aluminum - Bauxite, Al2O3·3H2O
What is the concentration of sulfuric acid used in the experiment?
0.5 mol L^-1
1 mol L^-1
1.5 mol L^-1
2 mol L^-1
What is the purpose of using an electronic balance in the experiment?
To measure the volume of sulfuric acid
To stir the solution
To weigh out 6 g of copper(II) carbonate
To record the observations
Which of the following is used to secure the graphite electrodes in the beaker?
Blue Tack
Alligator clips
Banana plugs
Wooden tongs
What voltage is set on the powerpack during the electrolysis in Part B of the experiment?
4 V
5 V
6 V
7 V
What should be done with the copper(II) sulfate after the experiment is completed?
Pour it down the drain
Dispose of it by pouring into the heavy metals waste bottle
Reuse it for another experiment
Leave it in the beaker for observation
How can you tell that a chemical reaction occurred when sulfuric acid was added to copper(II) carbonate, according to the analysis of results?
By weighing the copper(II) carbonate before and after the reaction
By observing the change in voltage on the powerpack
By recording the observations made during the experiment
By the color change of the solution
What is the main safety risk mentioned in the experiment?
Electric shock from the powerpack
Splashing chemicals onto skin or eyes
Inhalation of copper(II) carbonate dust
Overheating of the beaker
How can the safety risk be managed according to the document?
By using a fume hood
By wearing safety glasses and washing hands at the end of the experiment
By working in a well-ventilated area
By using a lower voltage on the powerpack
What is the main advantage of using molten salts for electrolysis over aqueous solutions?
Molten salts allow for higher temperatures to be reached.
Molten salts ensure that no competing reactions occur.
Molten salts are easier to prepare in a school laboratory.
Molten salts produce a greater variety of products.
At what temperature does magnesium chloride melt, making it suitable for electrolysis in molten form?
Above 70°C
Above 714°C
Above 100°C
Below 70°C
During the electrolysis of molten magnesium chloride, what occurs at the anode?
Reduction of Mg²⁺ ions to Mg(l)
Oxidation of Cl⁻ ions to Cl₂(g)
Reduction of Cl⁻ ions to Cl₂(g)
Oxidation of Mg²⁺ ions to Mg(l)
What is the standard electrode potential (E°) for the reduction of Mg²⁺ to Mg(l) at the cathode during the electrolysis of molten magnesium chloride?
E° = -1.36 V
E° = -2.36 V
E° = +1.36 V
E° = +2.36 V
Which piece of equipment is used to reach higher temperatures than a Bunsen burner during the electrolysis of molten magnesium chloride?
Powerpack
Ni crucible
Pt electrode
Meker burner
What is the overall reaction for the electrolytic cell described in the text?
Mg(s) + 2Cl⁻(aq) → Mg²⁺(aq) + Cl₂(g)
Mg²⁺(aq) + 2Cl⁻(aq) → Mg(s) + Cl₂(g)
Mg²⁺(aq) + 2Cl⁻(aq) → MgCl₂(aq)
Mg²⁺(aq) + 2Cl⁻(aq) → Mg(s) + 2Cl(g)
What is the E⁰ value for the electrolytic cell reaction provided in the text?
E⁰ = +3.72 V
E⁰ = -3.72 V
E⁰ = 0 V
E⁰ = +1.36 V
Why does the electrolytic cell reaction have a negative E⁰ value?
Because it is a spontaneous reaction.
Because it is an endothermic reaction.
Because it is not a spontaneous reaction.
Because it occurs at standard conditions.
What are the products of the electrolysis of concentrated copper(II) chloride solution?
Chlorine gas and copper metal
Hydrogen gas and copper metal
Oxygen gas and copper chloride
Chlorine gas and copper chloride
What is the purpose of using inert carbon electrodes in the electrolysis of concentrated copper(II) chloride solution?
To increase the voltage of the reaction
To produce chlorine gas and a layer of pure copper that sticks to the surface of the cathode
To reduce the amount of copper(II) ions in the solution
To act as a catalyst for the reaction
Which of the following is NOT an application of electroplating mentioned in the text?
Enhancing the appearance of car parts
Improving the performance of cutlery
Making jewelry more durable
Increasing the electrical conductivity of plastics
What is the final step in extracting copper from its ore using electrolysis, as used industrially?
Electroplating
Electrowinning
Electrorefining
Electroforming
During the electrorefining of copper, what is the purity percentage of the 'blister copper' used as the starting material?
About 90%
About 95%
About 98%
About 99.9%
In the electrorefining process for copper, what is the cathode made of?
Impure copper
Pure copper
Blister copper
Silver
What happens to the impurities during the electrorefining of copper?
They are oxidised and go into solution.
They are reduced to pure metal.
They stay in solution or fall to the bottom of the electrolytic cell.
They migrate towards the cathode.
What is the aim of the practical activity involving electroplating?
To purify copper using electrolysis
To silver-plate a piece of copper using electrolysis
To demonstrate the electrorefining of copper
To create a copper-plated silver object
What is the purpose of cleaning the piece of copper using sandpaper before starting the electrolytic process?
To increase the electrical resistance of the copper
To remove any impurities and oxides from the copper surface
To change the chemical composition of the copper
To decrease the thermal conductivity of the copper
Which electrode is connected to the positive terminal of the powerpack in this electrolytic cell?
Copper electrode
Graphite electrode
Silver electrode
Zinc electrode
Why should the copper(II) sulfate be disposed of by pouring it into the heavy metals waste bottle?
Because it can be reused in future experiments
Because it is safe to pour down the drain
Because it is a non-toxic substance
Because it contains heavy metals that should not be poured down the drain
What is the half-equation for the reaction occurring at the cathode during the electrolysis of molten copper(II) bromide?
Cu^2+ + 2e^- → Cu(s)
2Br^- → Br2(g) + 2e^-
Cu^2+ → Cu^2+ + 2e^-
2Br^- + 2e^- → 2Br
Why are inert electrodes such as carbon and platinum used in electrolysis?
Because they react with the electrolyte and dissolve
Because they are cheaper than other electrodes
Because they do not react with the electrolyte and remain unchanged
Because they increase the electrical conductivity of the solution
When predicting and explaining products from the electrolysis of aqueous solutions, which two factors must be considered when determining which chemical reaction occurs at the anode and cathode?
The temperature of the electrolyte and the concentration of the electrolyte.
The nature of the electrolyte and the concentration of the electrolyte.
The pressure of the electrolyte and the type of electrodes used.
The pH of the electrolyte and the duration of electrolysis.
What is the standard electrode potential (E°) for the oxidation of bromide ions (Br⁻) to bromine (Br₂)?
+1.23V
+0.34V
-0.83V
-1.08V
What is the standard electrode potential (E°) for the reduction of copper(II) ions (Cu²⁺) to copper (Cu)?
+1.23V
+0.34V
-0.83V
-1.08V
Which half-equation represents the reduction of water to form hydrogen and hydroxide ions?
O₂(g) + 4H⁺ + 4e⁻ → 2H₂O(l)
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq)
Br₂(l) + 2e⁻ → 2Br⁻(aq)
Cu²⁺(aq) + 2e⁻ → Cu(s)
What is the standard electrode potential (E°) for the reduction of water to form oxygen and hydrogen ions?
+1.23V
+0.34V
-0.83V
-1.08V
Which half-reaction is more likely to occur at the anode based on the least negative E° value?
2Br^-(aq) -> Br_2(l) + 2e^- E° = -1.08V
2Cl^-(aq) -> Cl_2(g) + 2e^- E° = -1.36V
2H_2O(l) -> O_2(g) + 4H^+(aq) + 4e^- E° = -1.23V
Cu^{2+}(aq) + 2e^- -> Cu(s) E° = +0.34V
Which half-reaction is preferred at the cathode based on the least negative E° value?
Cu^{2+}(aq) + 2e^- -> Cu(s) E° = +0.34V
2H_2O(l) -> O_2(g) + 4H^+(aq) + 4e^- E° = -1.23V
2Br^-(aq) -> Br_2(l) + 2e^- E° = -1.08V
2Cl^-(aq) -> Cl_2(g) + 2e^- E° = -1.36V
What is the overall cell voltage for the electrolytic cell described in the image?
-0.89V
-0.74V
-1.23V
+0.34V
Which species is reduced at the cathode in the electrolytic cell?
Bromine (Br)
Chlorine (Cl)
Oxygen (O)
Copper (Cu)
What is the correct overall reaction for the electrolytic cell?
Cu^{2+}(aq) + 2Br^-(aq) -> Cu(s) + Br_2(l)
2Cl^-(aq) + Cu^{2+}(aq) -> Cl_2(g) + Cu(s)
2H_2O(l) + Cu^{2+}(aq) -> O_2(g) + 4H^+(aq) + Cu(s)
2H_2O(l) + 2Br^-(aq) -> O_2(g) + 4H^+(aq) + Br_2(l)
Which of the following anions is more likely to be oxidized preferentially to the others in an aqueous solution?
Sulfate (SO₄²⁻)
Nitrate (NO₃⁻)
Phosphate (PO₄³⁻)
Chloride (Cl⁻)
What is the overall reaction for the electrolysis of a copper(II) sulfate solution, CuSO₄?
2Cu²⁺(aq) + 2H₂O(l) → O₂(g) + 4H⁺(aq) + 2Cu(s)
Cu²⁺(aq) + H₂O(l) → O₂(g) + 2H⁺(aq) + Cu(s)
2Cu²⁺(aq) + 2H₂O(l) → O₂(g) + 4H⁺(aq) + 2Cu(s) + 2e⁻
2Cu²⁺(aq) + 2H₂O(l) → O₂(g) + 4H⁺(aq) + 2Cu(s) E° = –0.89V
What is the effect of increasing the concentration of chloride ions in the electrolysis of aqueous solutions?
It increases the likelihood of water oxidation at the anode.
It decreases the likelihood of chloride ion oxidation at the anode.
It increases the likelihood of chloride ion oxidation at the anode.
It has no effect on the reactions occurring at the anode.
What is the anode reaction in more concentrated chloride solutions during electrolysis?
2H₂O(l) → O₂(g) + 4H⁺(aq) + 4e⁻
2Cl⁻(aq) → Cl₂(g) + 2e⁻
2Cl⁻(aq) → 2Cl₂(g) + 2e⁻
Cl⁻(aq) → Cl₂(g) + e⁻
Why is the electrolysis of an aqueous solution more complicated than the electrolysis of a molten substance?
Because in aqueous solutions, only one reaction can occur at the electrodes.
Because in aqueous solutions, no competitive reactions occur at the electrodes.
Because in aqueous solutions, there are competitive reactions at both the anode and the cathode.
Because in aqueous solutions, the concentration of the solution does not affect the preferred reaction at the electrodes.
When electrolysis of aqueous solutions of salts containing polyatomic ions such as nitrates, carbonates and sulfates is carried out, why is oxygen gas always produced at the anode?
Because the polyatomic ions are reduced preferentially to water.
Because the polyatomic ions are oxidized preferentially to water.
Because water is oxidized preferentially to the polyatomic ions.
Because the concentration of polyatomic ions does not affect the reaction at the anode.
Which of the following statements is true regarding the preferred reaction in a very dilute zinc solution electrolysis?
The reduction of zinc ions would be preferred because it has a more negative E° value.
The reduction of water would be preferred because it has a less negative E° value.
The reduction of zinc ions would be preferred because it has a less negative E° value.
The reduction of water would be preferred because it has a more negative E° value.
Electrolytic cells can be grouped into how many main categories?
One
Two
Three
Four
What is the anode reaction in the electrolysis of molten sodium chloride as shown in Figure 14.3.1?
Na+(l) → Na(l)
2Cl⁻(l) → Cl₂(g) + 2e⁻
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq)
Zn²⁺(aq) + 2e⁻ → Zn(s)
What is the cathode reaction in the electrolysis of molten sodium chloride as shown in Figure 14.3.1?
Na+(l) → Na(l)
2Cl⁻(l) → Cl₂(g) + 2e⁻
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq)
Zn²⁺(aq) + 2e⁻ → Zn(s)
What is the cathode reaction in the electrolysis of molten sodium chloride as shown in Figure 14.3.1?
Na+(l) → Na(l)
2Cl⁻(l) → Cl₂(g) + 2e⁻
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq)
Zn²⁺(aq) + 2e⁻ → Zn(s)
What is placed in a crucible during the electrolysis of molten sodium chloride?
A) A mixture of sodium chloride and water
B) Pure sodium chloride
C) Sodium chloride solution
D) Sodium hydroxide
What is the role of the electrode attached to the negative terminal of the power supply in the electrolysis of molten sodium chloride?
A) It serves as the anode.
B) It serves as the cathode.
C) It provides the sodium ions.
D) It releases chlorine gas.
During the electrolysis of molten sodium chloride, what happens to the sodium ions at the cathode?
A) They lose an electron and become sodium metal.
B) They gain an electron and become sodium metal.
C) They remain in the liquid state.
D) They combine with chlorine ions.
What is the overall cell reaction for the electrolysis of molten sodium chloride?
A) NaCl(l) → Na(s) + Cl2(g)
B) 2Na+(l) + 2Cl-(l) → 2Na(s) + Cl2(g)
C) 2Na+(l) + 2Cl-(l) → 2Na(l) + Cl2(g)
D) Na+(l) + Cl-(l) → Na(s) + 1/2Cl2(g)
What is the minimum voltage that must be supplied to the electrolytic cell for the reaction to occur?
A) 1.36 V
B) 2.71 V
C) 4.07 V
D) 0 V
What is the purpose of the inert carbon electrodes in the electrolysis of molten sodium chloride?
A) To react with sodium ions
B) To react with chlorine ions
C) To conduct electricity and serve as sites for oxidation and reduction
D) To increase the temperature of the molten salt
What is placed in a beaker to perform the electrolysis of a dilute sodium chloride solution?
A dilute sulfuric acid solution
A concentrated sodium chloride solution
A dilute sodium chloride solution
Pure water
Which electrode is attached to the negative terminal of the power supply during the electrolysis of aqueous solutions?
Anode
Cathode
Electrolyte
Powerpack
What are the two possible reactions that can occur at the cathode during the electrolysis of aqueous sodium chloride?
Na⁺(aq) + e⁻ → Na(s) and 2Cl⁻(aq) → Cl₂(g) + 2e⁻
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq) and Na⁺(aq) + e⁻ → Na(s)
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq) and 2Cl⁻(aq) → Cl₂(g) + 2e⁻
Na⁺(aq) + e⁻ → Na(s) and 2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq)
Which reaction is the preferred reaction at the cathode and why?
Na⁺(aq) + e⁻ → Na(s) because it has a more negative voltage
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq) because it has a less negative voltage
2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq) because it has a more negative voltage
Na⁺(aq) + e⁻ → Na(s) because it has a less negative voltage
What is the overall reaction that occurs in the electrolytic cell used for aqueous solutions of sodium chloride?
Na⁺(aq) + Cl⁻(aq) → Na(s) + Cl₂(g)
2H₂O(l) → 2H₂(g) + O₂(g)
2Na⁺(aq) + 2H₂O(l) + 2e⁻ → H₂(g) + 2NaOH(aq)
2Cl⁻(aq) → Cl₂(g) + 2e⁻
How much voltage must be supplied by an external power source to enable the preferred reaction to occur in the electrolytic cell?
1.23 V
2.06 V
2.71 V
1.36 V
When electrolyzing aqueous solutions, what principle determines the products formed at each electrode?
The concentration of the solution
The electrode material
The least negative E^circ value
The amount of electricity passed through the solution
What is the overall equation for the electrolysis of water with chloride ions present?
2H_2O(l) -> O_2(g) + 4H^+(aq) + 4e^-
2H_2O(l) + 2Cl^-(aq) -> H_2(g) + 2OH^-(aq) + Cl_2(g) + 2e^-
2H_2O(l) + 2Cl^-(aq) -> H_2(g) + 2OH^-(aq) + 2e^-
2H_2O(l) + 2Cl^-(aq) -> H_2(g) + 2OH^-(aq) + Cl_2(g)
What minimum voltage must be applied to electrolyse a 1.0 M solution of zinc(II) nitrate?
1.23 V
0.83 V
2.19 V
1.36 V
Define electrolysis.
The process of depositing a layer of metal onto a surface using an electric current.
The process of purifying metals by using an electric current.
The process of chemical decomposition produced by passing an electric current through a liquid or solution containing ions.
The process of combining different elements using an electric current.
Define electroplating.
The process of depositing a layer of metal onto a surface using an electric current.
The process of purifying metals by using an electric current.
The process of chemical decomposition produced by passing an electric current through a liquid or solution containing ions.
The process of combining different elements using an electric current.
Define electrorefining.
The process of depositing a layer of metal onto a surface using an electric current.
The process of purifying metals by using an electric current.
The process of chemical decomposition produced by passing an electric current through a liquid or solution containing ions.
The process of combining different elements using an electric current.
What is the anode reaction in an electrolysis experiment to decompose a sample of molten zinc bromide using graphite electrodes?
Zn^2+ + 2e^- → Zn
2Br^- → Br2 + 2e^-
2H2O + 2e^- → H2 + 2OH^-
Cu^2+ + 2e^- → Cu
What is the cathode reaction in the same electrolysis experiment mentioned above?
Zn^2+ + 2e^- → Zn
2Br^- → Br2 + 2e^-
2H2O + 2e^- → H2 + 2OH^-
Cu^2+ + 2e^- → Cu
When a concentrated sodium chloride solution is electrolyzed, chlorine gas is produced, but if the cell is allowed to run for an extended amount of time, the chlorine gas is slowly replaced by oxygen gas. Suggest a reason why.
The sodium ions start to react with water to form hydrogen gas.
The chloride ions are completely consumed, and water begins to decompose.
The concentration of sodium chloride increases, leading to the production of oxygen.
The temperature of the solution decreases, causing oxygen to be released.
In electrolysis, the anode and cathode are determined by:
the electrode potentials of the ions in the electrolyte
the connection of the electrodes to the external power supply
the site of the oxidation and reduction
the movement of ions in the electrolyte
The half-reaction that occurs at the anode during the electrolysis of a concentrated potassium bromide solution is:
Br2(aq) + 2e⁻ → 2Br⁻(aq)
2H2O(l) → O2(g) + 4H⁺(aq) + 4e⁻
2Br⁻(aq) → Br2(aq) + 2e⁻
K⁺(aq) + e⁻ → K(s)
When electroplating a coating of zinc onto a piece of iron, what will the anode and the electrolyte be?
Zinc and iron(II) nitrate
Iron and zinc nitrate
Zinc and zinc nitrate
Iron and iron(II) nitrate
What is the minimum voltage required to enable the electrolysis of dilute zinc sulfate to occur?
−2.75V
1.99V
−3.22V
0.47V
If the cell potential of an electrolytic cell has a negative sign, what can be said of the reaction it represents?
The reaction is spontaneous.
The reaction is non-spontaneous.
The reaction is at equilibrium.
The reaction is exothermic.
An electrolytic cell is comprised of two carbon electrodes dipping into a dilute copper(II) bromide solution. What will be the product at the cathode?
Oxygen gas
Bromine gas
Copper metal
Hydrogen gas
What is the purpose of adding a few drops of phenolphthalein indicator to the solution in the electrolysis experiment?
To measure the concentration of sodium chloride
To indicate the presence of basic or acidic solution
To increase the conductivity of the solution
To change the color of the solution for aesthetic purposes
Identify the anode in the experimental set-up shown in Figure 14.4.2.
Part A
Part B
Part C
Part D
Identify the cathode in the experimental set-up shown in Figure 14.4.2.
Part A
Part B
Part C
Part D
Suggest a reason why the amounts of gases produced during the electrolysis are not the same.
The gases have different molecular weights.
The gases are produced at different rates due to their chemical properties.
One gas dissolves in water more readily than the other.
The electrodes have different sizes.
