Electrolytic Cells questions

Which of the following is correct for electrolytic cells?

1. A Electrons move in the electrolyte from the cathode to the anode.
2. B Electrons move in the external circuit towards the cathode.
3. C Negative ions move in the external circuit towards the anode.
4. D Positive ions move in the electrolyte towards the anode.

All of the following happen in electrolytic cells, except ..........

1. A An oxidation process at the anode.
2. B Non-spontaneous reactions.
3. C Chemical decomposition of the electrolyte.
4. D Transfer of electrons from the cathode to the anode.

An electrolyte solution is electrically neutral, because ..........

1. A the number of cations in it equals the number of anions.
2. B the sum of the positive charges of its cations equals the sum of the negative charges of its anions.
3. C the positive charge on each cation equals the negative charge on each anion.
4. D the solvent can separate the cations from the anions.

Which of the following describes the movement of cations in electrolyte solutions?

1. A In electrolytic cells: towards the cathode, in galvanic cells: towards the anode half-cell
2. B In electrolytic cells: towards the anode, in galvanic cells: towards the cathode half-cell
3. C In electrolytic cells: towards the cathode, in galvanic cells: towards the cathode half-cell
4. D In electrolytic cells: towards the anode, in galvanic cells: towards the anode half-cell

Electrolysis of CuCl₂ solution between graphite electrodes causes all of the following, except ..........

1. A Copper cations are reduced at the cathode.
2. B Chlorine is evolved at the anode.
3. C The blue colour gradually fades.
4. D Graphite atoms are oxidized at the anode.

Which of the following happens during the electrolysis of copper(II) chloride solution? [Cu = 63.5 , Cl = 35.5]

1. A Reduction of copper atoms.
2. B Reduction of chloride ions.
3. C The mass of copper deposited is less than the mass of chlorine evolved.
4. D The mass of copper deposited is greater than the mass of chlorine evolved.

What substance is formed at the anode during the electrolysis of molten NaCl?

1. A Chlorine.
2. B Oxygen.
3. C Sodium.
4. D Hydrogen.

Which of the following processes takes place at the cathode of the cell for the electrolysis of molten lead(II) bromide?

1. A Pb → Pb²⁺ + 2e⁻
2. B Br₂ + 2e⁻ → 2Br⁻
3. C 2Br⁻ → Br₂ + 2e⁻
4. D Pb²⁺ + 2e⁻ → Pb

The reaction at the cathode of an electrolytic cell with graphite electrodes and dilute hydrochloric acid as the electrolyte is ..........

1. A H₂(g) → 2H⁺(aq) + 2e⁻
2. B Cl₂(g) + 2e⁻ → 2Cl⁻(aq)
3. C 2H⁺(aq) + 2e⁻ → H₂(g)
4. D 2Cl⁻(aq) → Cl₂(g) + 2e⁻

The process Ni²⁺(aq) + 2e⁻ → Ni⁰(s) takes place in ..........

1. A a galvanic cell at the cathode or an electrolytic cell at the anode.
2. B a galvanic cell or an electrolytic cell at the cathode.
3. C a galvanic cell or an electrolytic cell at the anode.
4. D a galvanic cell at the anode or an electrolytic cell at the cathode.

Comparing the galvanic cell with the electrolytic cell, we find that oxidation takes place at ..........

1. A the anode in both cells.
2. B the cathode in both cells.
3. C the anode in the galvanic cell only.
4. D the cathode in the galvanic cell only.

Which of the following describes the electrolytic cell?

1. A Electrode: anode, process: oxidation, electrons: gain
2. B Electrode: anode, process: reduction, electrons: loss
3. C Electrode: cathode, process: oxidation, electrons: loss
4. D Electrode: cathode, process: reduction, electrons: gain

In the electrolysis of molten NaI, a metal formed at one electrode and a brown substance at the other electrode.
What is the cathode half-cell reaction?

1. A 2I⁻ → I₂ + 2e⁻
2. B Na⁺ + e⁻ → Na
3. C I₂ + 2e⁻ → 2I⁻
4. D Na → Na⁺ + e⁻

From the opposite cell,
which of the following choices is correct?

1. A The mass of the positive electrode decreases.
2. B The mass of the negative electrode decreases.
3. C The mass of the cathode increases and the electrolyte concentration stays constant.
4. D The mass of the cathode increases and no change occurs in the mass of the anode.

Magnesium can be extracted from molten magnesium chloride by electrolysis.
Which of the following gives the two reactions at the positive and negative electrodes of the cell used?

1. A Positive electrode: Cl₂ + 2e⁻ → 2Cl⁻ , negative electrode: Mg → Mg²⁺ + 2e⁻
2. B Positive electrode: Cl₂ + 2e⁻ → 2Cl⁻ , negative electrode: Mg²⁺ + 2e⁻ → Mg
3. C Positive electrode: 2Cl⁻ → Cl₂ + 2e⁻ , negative electrode: Mg → Mg²⁺ + 2e⁻
4. D Positive electrode: 2Cl⁻ → Cl₂ + 2e⁻ , negative electrode: Mg²⁺ + 2e⁻ → Mg

An electrolytic cell in which the two processes at its electrodes are given by the following equations:
X²⁺(aq) + 2e⁻ → X(s)
2Y⁻(aq) → Y₂(g) + 2e⁻
Which of the following describes this cell?

1. A Process: X²⁺ + 2e⁻ → X at the anode, electrode mass after 15 min: decreases
2. B Process: X²⁺ + 2e⁻ → X at the cathode, electrode mass after 15 min: increases
3. C Process: 2Y⁻ → Y₂ + 2e⁻ at the anode, electrode mass after 15 min: increases
4. D Process: 2Y⁻ → Y₂ + 2e⁻ at the cathode, electrode mass after 15 min: decreases

The opposite figure shows the electrolysis of water acidified with sulphuric acid using two graphite electrodes. When X mol of electrons pass through the cell, 0.25X mol of .......... is evolved.

1. A O₂ at the anode.
2. B H₂ at the anode.
3. C O₂ at the cathode.
4. D H₂ at the cathode.

Which graph shows the mass of the cathode with time when a constant current is passed through molten zinc sulphate using zinc electrodes?

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

From the opposite figure:
What substances are formed at the graphite electrodes (1) and (2)?

1. A (1): Cu , (2): H₂
2. B (1): Cl₂ , (2): Cu
3. C (1): Cu , (2): Cl₂
4. D (1): O₂ , (2): Cu

From the opposite potentials:
A⁺ + e⁻ → A , E° = +0.52 V
B⁺ + e⁻ → B , E° = +0.25 V
Which of the following describes the electrochemical cell in which the metal A is oxidized and the ion B⁺ is reduced?

1. A A galvanic cell, its emf is +0.27 V
2. B A galvanic cell, its emf is −0.27 V
3. C An electrolytic cell, its emf is +0.27 V
4. D An electrolytic cell, its emf is −0.27 V

What quantity of electricity is consumed when a current of 0.1 A passes through an electrolyte solution for half an hour?

1. A 80 C
2. B 180 C
3. C 360 C
4. D 3600 C

What quantity of electricity results from passing a current of 2.5 A for 120 min through an electrolyte solution?

1. A 0.332 F
2. B 0.187 F
3. C 0.233 F
4. D 1.076 F

What current is needed to pass 0.36 F through an electrolyte solution in one hour?

1. A 9.65 A
2. B 579 A
3. C 0.965 A
4. D 5.79 A

What is the number of electrons transferred when a quantity of electricity of one coulomb passes through an electrolyte?

1. A 6.023 × 10²³ e⁻
2. B 1.64 × 10⁻²⁴ e⁻
3. C 6.24 × 10¹⁸ e⁻
4. D 6.24 × 10⁻²⁴ e⁻

When a current of 5 A passes through molten calcium chloride, 30 g of calcium [Ca = 40] is deposited in a time of ..........

1. A 8 h
2. B 10 h
3. C 16 h
4. D 80 h

A current of 1.2 A was passed through a solution of copper(II) ions, and all the copper in it was deposited; its mass was 0.2 g
What is the time taken to deposit all the copper in the solution? [Cu = 63.5]

1. A 253 s
2. B 507 s
3. C 1012 s
4. D 2024 s

What is the time needed to separate half the silver in 200 mL of 0.1 M silver nitrate solution using a current of 0.1 A?

1. A 40 min
2. B 80.8 min
3. C 120 min
4. D 160.8 min

What is the time needed to generate a current of 1 A («assuming it can be obtained») when a 100 g zinc rod is placed in 1 L of 1 M CuSO₄ solution? [Zn = 65.5]

1. A 80.42 h
2. B 53.6 h
3. C 24.6 h
4. D 1 h

What quantity of electricity is needed to deposit 6.57 g of gold [Au = 197] from an electrolyte containing Au³⁺ ions?

1. A 1 F
2. B 0.1 F
3. C 1 C
4. D 0.1 C

How many gram-equivalent masses of copper can be deposited at the cathode of the cell for the electrolysis of CuSO₄ solution after a quantity of electricity of 241250 C passes through it?

1. A 1
2. B 2
3. C 2.5
4. D 1.25

When 1.5 F passes through a solution of the chloride of metal (M), 0.5 mol of the metal (M) is deposited.
What is the molecular formula of the chloride of metal (M)?

1. A MCl
2. B MCl₂
3. C MCl₃
4. D M₂Cl

When a current of 1 A passes for 15 min through a solution of a metal salt, 0.173 g of the metal is deposited, so the equivalent mass of the metal is ..........

1. A 18.55 g
2. B 155.7 g
3. C 9.27 g
4. D 0.0016 g

When a current of 15 A passes for 50 min through a solution of a divalent metal, the mass of the cathode increased by 9.35 g
What is the gram atomic mass of this element?

1. A 20 g/atom
2. B 30 g/atom
3. C 40 g/atom
4. D 50 g/atom

The masses of the following substances can gain (or lose) 1 mol of electrons during electrochemical processes, except ..........

1. A 20 g of Ca²⁺ ions , [Ca = 40]
2. B 23 g of Na⁺ ions , [Na = 23]
3. C 16 g of O²⁻ ions , [O = 16]
4. D 35.5 g of Cl⁻ ions , [Cl = 35.5]

When 1 mol of electrons passes through an electrolytic cell, it can deposit ..........

1. A 65 g of Zn , [Zn = 65]
2. B 24 g of Mg , [Mg = 24]
3. C 11.5 g of Na , [Na = 23]
4. D 9 g of Al , [Al = 27]

What is the mass of the substance formed at the positive electrode when 0.5 F passes through molten silver bromide? [Ag = 108 , Br = 80]

1. A 27 g
2. B 40 g
3. C 54 g
4. D 80 g

A current of X A was passed for t s through an aqueous CuSO₄ solution, and an amount of copper [Cu = 63.5] was deposited that can be calculated from the relation ..........

1. A X t / (63.5 × 96500)
2. B X t / (31.75 × 96500)
3. C X t / (31.75 × t)
4. D 31.75 × (X t) / 96500

What amount of copper [Cu = 63.5] can be deposited from CuSO₄ solution when a quantity of electricity of 0.5 F passes through it?

1. A 31.75 g
2. B 63.5 g
3. C 15.875 g
4. D 127 g

When a quantity of electricity of (X) faradays passes through molten aluminium oxide, 13.5 g of aluminium [Al = 27] is deposited.
What is the value of (X)?

1. A 2 F
2. B 1.5 F
3. C 1 F
4. D 0.5 F

What quantity of electricity is needed to deposit 39 g of potassium [K = 39] from molten potassium fluoride?

1. A 96500 C
2. B 48250 C
3. C 193000 C
4. D 10000 C

Separating one mol of magnesium from molten MgCl₂ needs a quantity of electricity of ..........

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

The following chemical equation gives the products of the electrolysis of aqueous NaClO₃ solution:
NaClO₃ + H₂O → NaClO₄ + H₂
What quantity of electricity is needed to produce 0.5 mol of NaClO₄?

1. A 1 F
2. B 1.5 F
3. C 2 F
4. D 3 F

What quantity of electricity is needed to evolve 355 g of Cl₂ gas [Cl = 35.5] by the electrolysis of molten NaCl?

1. A 9.25 × 10⁴ C
2. B 9.65 × 10⁵ C
3. C 9.65 × 10⁴ C
4. D 4.83 × 10⁵ C

What quantity of electricity is needed to obtain all the chlorine in 500 mL of 4 M sodium chloride solution by electrolysis?

1. A 24129 C
2. B 48250 C
3. C 96500 C
4. D 193000 C

0.44 g of the metal (M), of atomic mass 88, is deposited when a current of 0.5 A passes for (32 min + 10 s) through its molten chloride.
What quantity of electricity is needed to deposit one mole of this metal?

1. A 0.2 F
2. B 0.4 F
3. C 2 F
4. D 4 F

When a quantity of electricity of 4 F passes through CuSO₄ solution, the number of moles of copper deposited equals ..........

1. A 3 mol
2. B 2 mol
3. C 1.5 mol
4. D 4 mol

What is the number of moles of electrons produced by consuming 0.347 g of lithium [Li = 6.94] in a lithium-ion battery?

1. A 3.47 mol e⁻
2. B 1 mol e⁻
3. C 0.5 mol e⁻
4. D 0.05 mol e⁻

What amount of chlorine gas [Cl = 35.5] is produced by the electrolysis of molten NaCl using a current of 1 A for 30 min?

1. A 0.66 mol
2. B 0.33 mol
3. C 0.66 g
4. D 0.33 g

Chromium is deposited by the electrolysis of a solution containing Cr⁶⁺ ions.
What is the number of moles of chromium deposited using a current of 8 A for 2 h?

1. A 0.3 mol
2. B 0.1 mol
3. C 0.9 mol
4. D 1.2 mol

In an electrolysis experiment, a quantity of electricity was passed through two electrolytes connected in series; 14 g of iron was deposited from a solution containing Fe²⁺(aq) ions, and 6.875 g of manganese.
What is the charge number of the manganese ion in its electrolyte solution? [Fe = 56 , Mn = 55]

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

The metal (M) used in galvanization can be obtained by the electrolysis of the molten chloride of this metal.
How many moles of the metal (M) can be obtained using a quantity of electricity of 9.65 C?

1. A 5 × 10⁻⁴ mol
2. B 1 × 10⁻⁴ mol
3. C 5 × 10⁻⁵ mol
4. D 1 × 10⁻⁵ mol

What is the volume of H₂ gas produced (at STP) by the electrolysis of acidified water when a current of 4 A passes through it for 30 min?

1. A 0.0836 L
2. B 0.0432 L
3. C 0.1672 L
4. D 0.836 L

What volume of oxygen gas can be liberated using a quantity of electricity of 96500 C (at STP)?

1. A 6.5 L
2. B 5.6 L
3. C 11.2 L
4. D 22.4 L

What current must pass for one hour through KI solution to form 10 g of iodine? [I = 127]

1. A 1.05 A
2. B 2.1 A
3. C 13.9 A
4. D 1.12 A

In the electrolysis of water acidified with sulphuric acid, 1.12 mL of hydrogen gas (at STP) is collected every second.
What is the current used in this process?

1. A 9.65 A
2. B 19.3 A
3. C 0.965 A
4. D 1.93 A

Water acidified with dilute sulphuric acid is electrolysed, forming O₂ and H₂ gases.
What current must pass for 3 h through the acidified water to obtain 0.5 L of O₂ gas (at STP)?

1. A 0.5 A
2. B 0.6 A
3. C 0.8 A
4. D 0.9 A

A current of 10 A was passed for 965 s through 1 L of 1 M HCl solution.
What is the pH of the solution at the end of the experiment?

1. A 0.8
2. B 0.2
3. C 0
4. D 0.0458

A quantity of electricity of 0.5 F was passed through 1 L of 2 M copper(II) chloride solution.
What is the concentration of the Cu²⁺ ions remaining in the electrolytic cell used?

1. A 0.25 M
2. B 0.5 M
3. C 4.5 M
4. D 1.75 M

When the same quantity of electricity is used for electrolysis in each of the following two cases:
Case (1): the electrolyte used is 1 M H₂SO₄(aq)
Case (2): the electrolyte used is 1 M HCl(aq)
the amount of hydrogen evolved in case (1) compared with the amount evolved in case (2) is ..........

1. A half the amount.
2. B a quarter of the amount.
3. C double the amount.
4. D the same amount.

When a quantity of electricity of 0.3 F passes through molten zinc chloride and molten scandium chloride, each separately, .......... are deposited.

1. A 1.5 mol of Zn , 1 mol of Sc
2. B 1.5 mol of Zn , 0.1 mol of Sc
3. C 0.15 mol of Zn , 0.1 mol of Sc
4. D 0.15 mol of Zn , 1 mol of Sc

Which of the following is the maximum mass of oxygen gas that can be produced by a quantity of electricity equal to the quantity that can produce 0.504 g of hydrogen gas? [H = 1 , O = 16]

1. A 0.4 g
2. B 2 g
3. C 4 g
4. D 8 g

A galvanic cell made of a Cd electrode in Cd(NO₃)₂ solution and a Zn electrode in Zn(NO₃)₂ solution. At the start of the experiment each electrode had a mass of 5 g, and after some time of operation one electrode had a mass of 4.75 g
Which electrode lost mass, and by how much did the mass of the other electrode increase? [Cd = 112.4 , Zn = 65.37]

1. A 0.43 g / Zn
2. B 0.145 g / Cd
3. C 0.145 g / Zn
4. D 0.43 g / Cd

The quantity of electricity used to deposit 18.25 g of copper [Cu = 63.5] from CuSO₄ solution is used to deposit 80 g of cerium [Ce = 140] from a solution of ..........

1. A CeNO₃
2. B Ce(NO₃)₂
3. C CeSO₄
4. D CeCl₄

A current of 1 A was passed for 1 h through three electrolyte solutions connected in series, containing Cu²⁺(aq), Ag⁺(aq) and Au³⁺(aq) ions.
Which order gives the masses of the metals deposited on the cathode of each cell? [Cu = 63.5 , Ag = 108 , Au = 197]

1. A Cu < Au < Ag
2. B Ag < Cu < Au
3. C Au < Cu < Ag
4. D Ag < Au < Cu

From the opposite figure: after a certain time, 6 g of titanium [Ti = 48] is deposited.
What is the mass of silver [Ag = 108] deposited on the cathode of the other cell?

1. A 6.8 g
2. B 13.5 g
3. C 27 g
4. D 54 g

The same quantity of electricity was used to deposit:
• silver from a solution containing Ag⁺ ions
• copper from a solution containing Cu²⁺ ions
Which of the following describes the amount of silver deposited? [Ag = 108 , Cu = 63.5]

1. A Its mass equals half the mass of copper deposited.
2. B Its mass equals double the mass of copper deposited.
3. C Its number of moles equals half the number of moles of copper deposited.
4. D Its number of moles equals double the number of moles of copper deposited.

An electric current was passed through two cells connected in series; the first contains AgNO₃ solution and the second ZnSO₄ solution, and the electrodes in both are platinum.
What is the ratio of the mass of silver deposited to the mass of zinc deposited, respectively? [Ag = 108 , Zn = 65]

1. A 108 / 65
2. B 65 / 108
3. C 108 / 32.5
4. D 32.5 / 108

What masses of aluminium and silver could be deposited when the same quantity of electricity passes through two solutions of their salts connected in series? [Al = 27 , Ag = 108]

1. A 1 g of Al , 12 g of Ag
2. B 2 g of Al , 6 g of Ag
3. C 12 g of Al , 1 g of Ag
4. D 3 g of Al , 8 g of Ag

The same quantity of electricity was used in the electrolysis of molten magnesium chloride and molten titanium chloride, and 4.8 g of each of Mg and Ti was deposited.
What is the formula of the titanium chloride used? [Mg = 24 , Ti = 48]

1. A TiCl
2. B TiCl₂
3. C TiCl₃
4. D TiCl₄

A current of a A was passed for 3 min through molten copper(II) chloride, and 10 mL of chlorine gas (at STP) was evolved at the anode.
What current is needed to produce the same volume of oxygen gas in the same time by the electrolysis of sulphuric acid (at STP)?

1. A 0.5a A
2. B a A
3. C 2a A
4. D 4a A

When a quantity of electricity passes through a sulphuric acid solution, 2.24 L of hydrogen gas (at STP) can be collected. When the same quantity of electricity passes through copper(II) sulphate solution, a mass of copper [Cu = 63.5] of .......... can be deposited.

1. A 1.59 g
2. B 3.18 g
3. C 6.35 g
4. D 12.7 g

Copper can be deposited from either of the two cases:
• (X): copper(II) sulphate solution.
• (Y): copper(I) chloride solution.
Using the same quantity of electricity, the amount of copper deposited in electrolytic cell ..........

1. A (X) is double.
2. B (Y) is double.
3. C (Y) is a quarter.
4. D (X) is a quarter.

In the electrolysis of silver nitrate solution, 1.08 g of silver [Ag = 108] was deposited on the cathode.
What is the volume of oxygen gas evolved at the anode (at STP)?

1. A 0.028 L
2. B 0.056 L
3. C 0.168 L
4. D 0.224 L

From the opposite table:
The same quantity of electricity was passed through three electrolytic cells containing three different solutions of salts of the metals (X), (Y) and (Z).
What are the valencies of these metals, respectively?

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

The quantity of electricity needed to form 1 mol of O₂ gas equals the quantity of electricity needed to form ..........

1. A 1 mol of Cl₂ gas
2. B 2 mol of F₂ gas
3. C 1 mol of Ca metal
4. D 1 mol of Al metal

An object was coated with a layer of the metal (X) by electrolysis, using the data shown in the opposite table:
What is the oxidation number of (X) in the electrolyte used?

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

The following figure shows four cells with identical graphite electrodes:
After some time, the increase in the mass of the cathode is greatest in cell .......... [Ag = 108 , Ca = 40 , Cu = 63.5 , Al = 27]

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

An electrochemical cell whose overall reaction is given by the equation:
Cu(s) + Mn²⁺(aq) → Cu²⁺(aq) + Mn(s)
Given that:
• Mn(s) → Mn²⁺(aq) + 2e⁻ , E° = +1.03 V
• Cu²⁺(aq) + 2e⁻ → Cu(s) , E° = +0.34 V
What type of electrochemical cell is this? Explain.

From the opposite figure:
(1) What is the type of each of:
(a) cell (A).
(b) cell (B).
(2) Write the equation of the reaction at:
(a) the graphite electrode (X).
(b) the graphite electrode (Y).

The electrolysis of molten strontium chloride SrCl₂ produces strontium metal and chlorine gas.
Write the ionic equation for the reaction at each of:
(1) the anode.
(2) the cathode.

From the experiment shown in the opposite figure:
What is the ratio between the volumes of the two gases evolved in the tubes (P) and (Q) from the electrolysis of acidified water? Write the ionic equations that support your answer.

Fe³⁺ ions can be converted into Fe²⁺ ions and vice versa:
(1) Which of these two processes happens more easily? Explain.
(2) Calculate the quantity of electricity in faradays needed to convert 1 mol of Fe³⁺ into Fe²⁺

A silver nitrate solution was divided between two electrolytic cells. A current of 0.965 A was passed through the first cell for 1000 s, and a quantity of electricity of 9650 C through the second cell:
(1) Calculate the mass of silver [Ag = 108] deposited on the cathode of each cell, and explain.
(2) What scientific rule supports your answer?

Two electrolytic cells connected in series; the first contains silver nitrate solution AgNO₃ and the second copper sulphate solution CuSO₄. After the current passed through them for a certain time, the mass of the cathode in the first cell increased by 1.078 g
By how much did the mass of the cathode of the second cell increase? [Ag = 108 , Cu = 63.5]

Calculate the volume of oxygen gas (at STP) produced by passing a quantity of electricity of 5 F through an electrolyte solution according to the anode reaction:
2O²⁻(aq) → O₂(g) + 4e⁻

Give the scientific reason for each of the following:
(1) The gram-equivalent mass of sodium [Na = 23] equals its molar mass, while the gram-equivalent mass of magnesium [Mg = 24] equals half its molar mass.
(2) The quantity of electricity needed to produce 32 g of oxygen gas O₂ by electrolysis is double the quantity needed to produce 2 g of hydrogen gas H₂ [O = 16 , H = 1]

An electric current is passed through copper(II) nitrate solution using a pure copper electrode connected to the positive terminal of the battery and an iron electrode connected to the negative terminal of the battery.
Which of the following is correct while the current passes?

1. A The concentration of nitrate ions in the solution increases and the concentration of copper ions stays constant.
2. B Copper ions are reduced at the cathode and the solution stays electrically neutral.
3. C The concentration of copper ions increases and the concentration of nitrate ions in the solution decreases.
4. D The copper of the anode is oxidized and the total charge of the solution becomes positive.

Three electrolytic cells connected in series, each containing inert electrodes and the following electrolytes:
- molten Al₂O₃
- molten Mg₃N₂
- molten NaCl
Which of the following gives the ratio between the volumes of the gases evolved from these cells?

1. A Oxygen gas: 2 , nitrogen gas: 3 , chlorine gas: 1
2. B Oxygen gas: 0.166 , nitrogen gas: 0.250 , chlorine gas: 0.330
3. C Oxygen gas: 1 , nitrogen gas: 2 , chlorine gas: 3
4. D Oxygen gas: 0.250 , nitrogen gas: 0.166 , chlorine gas: 0.500

Which of the following happens in the electrolytic cell in the opposite figure?

1. A Reduction of bromide ions Br⁻(aq) at electrode (A).
2. B Oxidation of bromide ions Br⁻(aq) at electrode (B).
3. C Reduction of silver ions Ag⁺(aq), which are deposited at electrode (B).
4. D Oxidation of silver ions Ag⁺(aq), which are deposited at electrode (A).

A current of 10 amperes was passed for 10 hours through molten sodium chloride.
Which of the following gives the mass of sodium produced? [Na = 23]

1. A 42.1 g
2. B 423.2 g
3. C 85.8 g
4. D 21.1 g

The following figure shows three cells connected in series:
When a current passes through the circuit for a quarter of an hour, which electrode increases in mass at the greatest rate? [Ni = 58.7 g/mol , Ag = 108 g/mol , Cu = 63.5 g/mol]

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

One faraday is passed through molten sodium chloride.
Which of the following gives the number of moles of gas evolved?

1. A 0.5 mol
2. B 1 mol
3. C 1.5 mol
4. D 2 mol

Which of the following is the anode half-reaction during the electrolysis of molten sodium hydride NaH between graphite electrodes?

1. A 2Na⁺ + 2e⁻ → 2Na
2. B 2Na → 2Na⁺ + 2e⁻
3. C H₂⁻ → 2H⁺ + 2e⁻
4. D 2H⁻ → H₂(g) + 2e⁻

Which of the following metals deposits 18 g when 1.5 F passes through one of its molten salts? [Na = 23 , Mg = 24 , Ca = 40 , K = 39]

1. A Na
2. B Mg
3. C Ca
4. D K

In the Daniell cell, if the mass of zinc consumed is 6.5 g, the mass of copper deposited is .......... [Zn = 65 , Cu = 63.5]

1. A 6.5 g and it is deposited at the positive pole.
2. B 6.35 g and it is deposited in the anode half-cell.
3. C 6.35 g and it is deposited at the positive pole.
4. D 3.25 g and it is deposited in the cathode half-cell.

Which of the following is the reaction at the anode of the cell for the electrolysis of molten potassium bromide?

1. A 2K⁺ + 2e⁻ → 2K⁰
2. B 2Br⁻ → Br₂ + 2e⁻
3. C 2K⁺ → 2K⁰ − 2e⁻
4. D Br₂ + 2e⁻ → 2Br⁻

The quantity of electricity needed to deposit 1 mol of Au³⁺ can deposit 1.5 mol of ..........

1. A Na⁺
2. B Mg²⁺
3. C Cu⁺
4. D Al³⁺

Permanganate ions MnO₄⁻ can be prepared by the electrolysis of a solution containing manganese ions Mn²⁺ according to the opposite reaction:
Mn²⁺ + 4H₂O → MnO₄⁻ + 8H⁺ + 5e⁻
The quantity of electricity needed to prepare 0.2 mol of permanganate ions equals ..........

1. A 48250 C
2. B 193000 C
3. C 19300 C
4. D 96500 C

Which of the following gives the reactions at the electrodes of a cell for the electrolysis of copper chloride solution using platinum electrodes?

1. A Reaction at the anode: Cu → Cu²⁺ + 2e⁻ , reaction at the cathode: Cl₂ + 2e⁻ → 2Cl⁻
2. B Reaction at the anode: 2Cl⁻ → Cl₂ + 2e⁻ , reaction at the cathode: Cu²⁺ + 2e⁻ → Cu
3. C Reaction at the anode: Cu²⁺ + 2e⁻ → Cu , reaction at the cathode: Cl₂ + 2e⁻ → 2Cl⁻
4. D Reaction at the anode: Cl₂ + 2e⁻ → 2Cl⁻ , reaction at the cathode: Cu → Cu²⁺ + 2e⁻

The opposite figure shows two cells containing different molten salts. After the current passed through the two cells for some time, the mass of the substance formed at the cathode of cell (1) was double that formed at the cathode of cell (2).
Which of the following gives the molten salts in the two cells and the substance formed at the electrodes (X) and (Y)? [Cl = 35.5 , Al = 27 , Au = 195 , Mg = 24 , Zn = 65 , Cr = 52]

1. A Cell (1): AuCl₃ , gold is deposited at (X) / Cell (2): ZnCl₂ , chlorine gas is evolved at (Y)
2. B Cell (1): AuCl₃ , gold is deposited at (X) / Cell (2): ZnCl₂ , zinc is deposited at (Y)
3. C Cell (1): CrCl₃ , chlorine gas is evolved at (X) / Cell (2): AlCl₃ , chlorine gas is evolved at (Y)
4. D Cell (1): CrCl₃ , chromium is deposited at (X) / Cell (2): MgCl₂ , chlorine gas is evolved at (Y)

When a spoon is plated with a layer of gold using a cell containing an electrolyte solution of AuCl₃, 0.5 mol of electrons was passed through the solution.
Which of the following describes the changes that happen during the electrolysis? [Au = 197 g/mol]

1. A Increase in the mass of the spoon: 10.94 g , concentration of gold ions in the solution: decreases
2. B Increase in the mass of the spoon: 32.8 g , concentration of gold ions in the solution: increases
3. C Increase in the mass of the spoon: 32.8 g , concentration of gold ions in the solution: stays constant
4. D Increase in the mass of the spoon: 10.94 g , concentration of gold ions in the solution: stays constant

Which of the following describes what happens in the electrolysis of copper sulphate solution between copper electrodes?

1. A The mass of the anode increases and the concentration of copper ions in the solution does not change.
2. B The mass of the cathode decreases and the concentration of copper ions in the solution increases.
3. C The mass of the anode decreases and the concentration of copper ions in the solution decreases.
4. D The mass of the cathode increases and the concentration of copper ions in the solution does not change.

The following figure shows several electrolytic cells connected in series:
In which of the cells shown does the mass of the cathode increase the most? [Al = 27 , Pb = 208 , Ag = 108 , Cu = 63.5]

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

When 0.1 F is passed through 5.85 g of pure molten sodium chloride,
which of the following results? [Na = 23 , Cl = 35.5]

1. A The melt decomposes partly and 4.6 g of sodium is deposited.
2. B The melt decomposes completely and 2.3 g of sodium is deposited.
3. C The melt decomposes completely and 7.1 g of chlorine gas is evolved.
4. D The melt decomposes partly and 3.55 g of chlorine gas is evolved.

Which of the following represents the reaction at the cathode of an electrolytic cell containing molten potassium bromide?

1. A Br₂ + 2e⁻ → 2Br⁻
2. B 2K → 2K⁺ + 2e⁻
3. C 2Br⁻ → Br₂ + 2e⁻
4. D 2K⁺ + 2e⁻ → 2K

When a current of 5 A is passed for 15 minutes through 5 g of pure molten potassium chloride KCl, which of the following is correct? [K = 39 , Cl = 35.5]

1. A The melt decomposed completely and 1.82 g of potassium was deposited.
2. B The melt decomposed completely and 1.65 g of chlorine was evolved.
3. C 3.47 g of the melt decomposed and 1.65 g of potassium was deposited.
4. D The melt did not decompose completely and 1.53 g remained undecomposed.

Four elements (X), (Y), (Z) and (W) whose electrode potentials are shown in the opposite graph.
Which of the following choices is correct?

1. A The cell made of the electrodes (W) and (Z) is electrolytic and the element (W) is the cathode.
2. B The cell made of the electrodes (Y) and (Z) is galvanic, gives (emf = 0.6 V), and the element (Z) is the anode.
3. C The cell made of the electrodes (W) and (Y) is electrolytic and the element (Y) is the cathode.
4. D The cell made of the electrodes (W) and (X) is galvanic, gives (emf = 2.6 V), and the element (X) is the anode.

Given that:
• X²⁺ + 2e⁻ → X , E° = −0.23 V
• Y − 2e⁻ → Y²⁺ , E° = −0.4 V
When an electric current is passed between graphite electrodes through a solution containing the chlorides of X²⁺ and Y²⁺ at equal concentrations, which of the following choices is correct?

1. A The mass of the cathode increases because the metal (Y) is deposited.
2. B The mass of the anode increases because the metal (X) is deposited.
3. C Chlorine gas is evolved at the cathode.
4. D The metal (X) is deposited at the anode.

When an electric current is passed through molten XCl₄, 33.6 L of chlorine gas at STP is evolved at the anode, so the number of moles of the element (X) deposited at the cathode equals ..........

1. A 1.5 mol
2. B 0.5 mol
3. C 0.75 mol
4. D 0.375 mol

If the quantity of electricity needed to deposit the equivalent mass of a metal equals the quantity needed to deposit 1 mol of it, which of the following correctly describes this process?

1. A One mole of the metal ion gains one mole of electrons.
2. B One mole of the metal loses one mole of electrons.
3. C One mole of the metal ion gains 2 moles of electrons.
4. D One mole of the metal loses 2 moles of electrons.

When 10 g of the element (A) is deposited according to the equation: A²⁺ + 2e⁻ → A , the quantity of electricity equals .......... [A = 63.5]

1. A 0.315 F
2. B 0.675 C
3. C 15196 C
4. D 30393 F

The quantity of electricity needed to evolve 1.204 × 10²³ molecules of oxygen gas in the electrolysis of acidified water is ..........

1. A 0.8 F
2. B 0.4 F
3. C 9650 C
4. D 19300 C

The quantity of electricity in faradays needed to deposit 0.5 g of gold on a metal medal by electrolysis, according to the equation Au³⁺ + 3e⁻ → Au⁰ , given that [Au = 196.98], equals ..........

1. A 2.53 × 10⁻³ F
2. B 7.61 F
3. C 7.61 × 10⁻³ F
4. D 2.53 F

When a quantity of electricity of 5000 C passes through an aqueous solution of the chloride of the element (X), 3.4 g of the element (X) is deposited, so its equivalent mass equals ..........

1. A 32.8 g
2. B 65.6 g
3. C 98.4 g
4. D 196.9 g

When a quantity of electricity passes through molten magnesium nitride, 48 g of magnesium is deposited at the cathode, so the volume of nitrogen gas evolved at the anode (STP) is .......... [given that Mg = 24 , N = 14]

1. A 14.93 L
2. B 22.4 L
3. C 44.8 L
4. D 33.6 L

The opposite figure shows an electrolytic cell for molten iron(III) oxide. When a current of 10 A passes for two hours through molten iron(III) oxide, the volume of the gas evolved at the anode (STP) is ..........

1. A 8.34 L
2. B 16.68 L
3. C 12.51 L
4. D 4.18 L

In the opposite reaction taking place in an electric cell:
Ni⁰(s) + 2Ag⁺(aq) → Ni²⁺(aq) + 2Ag⁰(s)
Given that:
• Ni⁰(s) → Ni²⁺(aq) + 2e⁻ , E° = +0.23 V
• 2Ag⁺(aq) + 2e⁻ → 2Ag⁰(s) , E° = +0.8 V
which of the following is correct?

1. A The cell is electrolytic, emf = −1.03 V
2. B The cell is galvanic, emf = 1.03 V
3. C The cell is galvanic, emf = 0.564 V
4. D The cell is electrolytic, emf = −0.564 V

In the cell whose electrodes are iron and tin, given that:
• Fe(s) → Fe²⁺(aq) + 2e⁻ , E° = 0.409 V
• Sn²⁺(aq) + 2e⁻ → Sn(s) , E° = 0.150 V
which of the following is correct?

1. A Iron is the anode, and the emf of the cell is positive.
2. B Iron is the cathode, and the emf of the cell is negative.
3. C Tin is the anode, and the emf of the cell is positive.
4. D Tin is the cathode, and the emf of the cell is negative.

The following equations give the two half-cell reactions of an electric cell:
• 2Ni³⁺ + 2e⁻ → 2Ni²⁺ , E° = +0.898 V
• Cd²⁺ + 2e⁻ → Cd⁰ , E° = −0.402 V
The non-spontaneous oxidation reaction in the cell is ..........

1. A Cd⁰ → Cd²⁺ + 2e⁻ , E° = +0.402 V
2. B 2Ni²⁺ → 2Ni³⁺ + 2e⁻ , E° = −0.898 V
3. C Cd²⁺ + 2e⁻ → Cd⁰ , E° = −0.402 V
4. D 2Ni³⁺ + 2e⁻ → 2Ni²⁺ , E° = +0.898 V

In the opposite figure: cell (1) contains molten sodium chloride and cell (2) contains molten potassium bromide. When each of them is electrolysed, the substances formed at the electrodes (X , Y , Z , L) are ..........

1. A (X): H₂ , (Y): Cl₂ , (Z): Br₂ , (L): K
2. B (X): Cl₂ , (Y): Na , (Z): K , (L): Br₂
3. C (X): Cl₂ , (Y): Na , (Z): Br₂ , (L): K
4. D (X): H₂ , (Y): Cl₂ , (Z): K , (L): Br₂

When a quantity of electricity passes through two cells connected in series, the first containing Pb(NO₃)₂ solution, 8.28 g of lead is deposited, while in the second cell the reaction X⁴⁺ + 3e⁻ → X⁺ takes place.
Calculate the number of moles of X⁺ formed [Pb = 207]