Galvanic Cells questions

From the opposite reactions:
(1) BaCl₂(aq) + H₂SO₄(aq) → BaSO₄(s) + 2HCl(aq)
(2) 2H₂O₂(aq) → 2H₂O(l) + O₂(g)
(3) NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)
(4) Fe₂O₃(s) + 2Al(s) → Al₂O₃(s) + 2Fe(s)
Which of the following are two redox (oxidation-reduction) reactions?

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

Which of the following equations represents a redox reaction?

1. A Pb²⁺(aq) + 2Cl⁻(aq) → PbCl₂(s)
2. B CaO(s) + CO₂(g) → CaCO₃(s)
3. C Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
4. D HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

Which of the following redox equations is balanced?

1. A Cr(s) + 3Fe²⁺(aq) → 2Cr³⁺(aq) + Fe(s)
2. B Pb(s) + 2H⁺(aq) → Pb²⁺(aq) + H₂(g)
3. C Pb(s) + Ag⁺(aq) → Pb²⁺(aq) + Ag(s)
4. D Zn(s) + Br₂(aq) → Zn²⁺(aq) + Br⁻(aq)

In the reaction: Mg(s) + Cl₂(g) → MgCl₂(s) the correct oxidation half-reaction is ..........

1. A Mg + 2e⁻ → Mg²⁺
2. B Cl₂ + 2e⁻ → 2Cl⁻
3. C Mg → Mg²⁺ + 2e⁻
4. D Cl₂ → 2Cl⁻ + 2e⁻

Oxidation and reduction take place when iron(II) sulphate solution is added to ..........

1. A sodium hydroxide solution.
2. B acidified potassium permanganate solution.
3. C silver nitrate solution.
4. D ammonia solution.

In the redox reaction: Al + MnO₄⁻ + 2H₂O → Al(OH)₄⁻ + MnO₂
oxidation takes place for ..........

1. A Al
2. B MnO₄⁻
3. C Al(OH)₄⁻
4. D MnO₂

In the reaction: Pb(s) + Cu²⁺(aq) → Pb²⁺(aq) + Cu(s) the reducing agent is ..........

1. A Pb²⁺(aq)
2. B Cu²⁺(aq)
3. C Pb(s)
4. D Cu(s)

In the reaction: 2Cs(s) + Cl₂(g) → 2CsCl(s)
Which of the following describes the role of Cl₂ in this reaction?

1. A Reducing agent.
2. B Oxidizing agent.
3. C Electron donor.
4. D Catalyst.

Which of the following equations represents a reduction that forms a stable ion?

1. A Cr²⁺ → Cr³⁺ + e⁻
2. B V²⁺ → V³⁺ + e⁻
3. C Mn³⁺ + e⁻ → Mn²⁺
4. D Ti⁴⁺ + e⁻ → Ti³⁺

The oxidation number of a reducing agent can change from ..........

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

The following equation represents a redox reaction: Mn²⁺ + IO₃⁻ + H₂O → MnO₄⁻ + ½I₂ + 2H⁺
The reducing agent in it is ..........

1. A I₂
2. B IO₃⁻
3. C H₂O
4. D Mn²⁺

From the ionic equation: xFe²⁺(aq) + Cr₂O₇²⁻(aq) + 14H⁺(aq) → xFe³⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)
What is the value of the coefficient (x)?

1. A 6
2. B 4
3. C 3
4. D 2

How many moles of electrons are needed to decolourize 1 mol of permanganate ion in an acidic medium?

1. A 5
2. B 4
3. C 3
4. D 2

Which of the following describes the change in the oxidation numbers of iodine and sulphur in the reaction of hydrogen iodide with concentrated sulphuric acid?

1. A Iodine: -1 → 0 , sulphur: +6 → +2
2. B Iodine: +1 → 0 , sulphur: -6 → -2
3. C Iodine: +1 → 0 , sulphur: -6 → +4
4. D Iodine: -1 → 0 , sulphur: +6 → +4

Passing CO₂ gas over hot coal produces compound (X).
Which of the following reactions cannot take place?

1. A X + A₂(SO₄)₃ → ASO₄ + Y
2. B X + ZO₄⁻ → ZO₂ + Y
3. C X + A(NO₃)₃ → A(NO₃)₂ + Y
4. D X + ZSO₃ → ZSO₄ + Y

A zinc rod is placed in copper(II) sulphate solution.
Which of the following graphs represents [Zn²⁺] with time?

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

A scandium rod is placed in iron(III) chloride solution.
Which of the following is incorrect?

1. A Oxidation and reduction take place.
2. B [Fe³⁺] decreases and [Cl⁻] does not change.
3. C The mass of the consumed substance is greater than the mass of the deposited substance.
4. D The number of moles of the deposited substance = the number of moles of the consumed substance.

All of the following happen when a piece of zinc is placed in copper(II) sulphate solution, except ..........

1. A The piece of zinc becomes coated with a layer of copper.
2. B The mass of zinc decreases.
3. C Electrical energy can be obtained.
4. D The colour of the solution fades.

The reaction in a galvanic cell is represented by the ionic equation: Co²⁺(aq) + Fe(s) → Co(s) + Fe²⁺(aq)
Which of the following describes the reaction that takes place?

1. A Cobalt ions are oxidized.
2. B Cobalt ions are reduced by losing electrons.
3. C Iron atoms are oxidized.
4. D Iron atoms are reduced by gaining electrons.

The following redox reaction takes place in a galvanic cell: 2Au³⁺ + 3Cu → 3Cu²⁺ + 2Au
What happens at the cathode of this cell?

1. A Gold atoms lose electrons.
2. B Gold ions gain electrons.
3. C Copper atoms lose electrons.
4. D Copper ions gain electrons.

Reduction in a galvanic cell happens to ..........

1. A the anode rod.
2. B the cathode rod.
3. C the cations of the anode electrolyte.
4. D the cations of the cathode electrolyte.

The opposite figure represents a galvanic cell.
Which of the following represents the anode reaction in this cell?

1. A Cu → Cu²⁺ + 2e⁻
2. B Cu²⁺ + 2e⁻ → Cu
3. C Mg → Mg²⁺ + 2e⁻
4. D Mg²⁺ + 2e⁻ → Mg

When a Daniell cell works, the ions move between the two half-cells through ..........

1. A the anode.
2. B the cathode.
3. C the salt bridge.
4. D the external circuit.

The opposite reaction takes place in a galvanic cell: Zn + Fe²⁺ → Zn²⁺ + Fe
Which of the following is correct?

1. A Zinc is the cathode.
2. B Iron is the cathode.
3. C Reduction takes place at the zinc electrode.
4. D Oxidation takes place at the iron electrode.

Which of the following represents a half-cell reaction?

1. A IO₃⁻ + 6H⁺ + 5e⁻ → I₂ + 3H₂O
2. B IO₃⁻ + 6H⁺ + 4e⁻ → ½I₂ + 3H₂O
3. C IO₃⁻ + 6H⁺ → ½I₂ + 3H₂O + 5e⁻
4. D IO₃⁻ + 6H⁺ + 5e⁻ → ½I₂ + 3H₂O

A galvanic cell consists of a Zn electrode dipped in a 0.1 M solution of Zn²⁺(aq) ions, and a Cu electrode dipped in a 0.1 M solution of Cu²⁺(aq) ions.
Which of the following graphs represents the concentration of Zn²⁺(aq) and Cu²⁺(aq) ions in the electrolyte of each half-cell with time?

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

The opposite figure represents a galvanic cell.
What happens when this cell works?

1. A Copper ions move towards the salt bridge.
2. B Cations move towards the zinc electrode.
3. C The mass of the copper electrode increases.
4. D The mass of the zinc electrode increases.

The opposite figure represents an electric cell made of iron and copper electrodes.
Which of the following is correct?

1. A Fe : (1) , K⁺ : (2)
2. B Cu : (1) , NO₃⁻ : (2)
3. C Cu : (1) , K⁺ : (3)
4. D Fe : (1) , K⁺ : (3)

The opposite figure represents a galvanic cell.
Which of the following is correct?

1. A Zn²⁺ : (1) , SO₄²⁻ : (2) , Ba²⁺ : (3)
2. B Ba²⁺ : (1) , SO₄²⁻ : (2) , Cu²⁺ : (3)
3. C Cu²⁺ : (1) , Cl⁻ : (2) , Pb²⁺ : (3)
4. D Zn²⁺ : (1) , SO₄²⁻ : (2) , K⁺ : (3)

After the galvanic cell shown in the opposite figure worked for several hours, it was noticed that:
• the colour of the A²⁺ solution fades.
• the colour of the B²⁺ solution deepens.
Which of the following describes this cell?

1. A Electrons move from electrode (A) to electrode (B).
2. B The mass of electrode (B) increased after hours of operation.
3. C The salt-bridge anions move to half-cell (B).
4. D Electrode (A) is the reducing agent.

In the opposite galvanic cell.
Which of the following is correct?

1. A The mass of (A) decreases.
2. B Electrons move from (B) to (A).
3. C The colour of electrolyte (B) deepens.
4. D (A) is the cathode , (B) is the anode.

Which of the following describes the galvanic cell shown in the opposite figure?

1. A Electrons flow in the external wire from Cu to (M).
2. B The reduction potential of (M) is greater than that of Cu
3. C The cell reaction is: 2M + 3Cu²⁺ → 2M³⁺ + 3Cu
4. D The cell reaction is: Cu + M²⁺ → Cu²⁺ + M

A galvanic cell whose anode is a divalent metal (A) and whose cathode is a trivalent metal (B); the balanced overall reaction of this cell is ..........

1. A A + B³⁺ → A²⁺ + B
2. B B + A²⁺ → B³⁺ + A
3. C 3A + 2B³⁺ → 3A²⁺ + 2B
4. D 2B + 3A²⁺ → 2B³⁺ + 3A

The salt bridge in galvanic cells neutralizes ..........

1. A anions only.
2. B electrons.
3. C cations only.
4. D ions.

The following redox equation represents a galvanic cell: Ni(s) + Pb²⁺(aq) → Ni²⁺(aq) + Pb(s)
The salt bridge in this cell is used to connect ..........

1. A Pb(s) with Ni(s)
2. B Ni²⁺(aq) with Pb²⁺(aq)
3. C Ni²⁺(aq) with Ni(s)
4. D Pb²⁺(aq) with Pb(s)

All of the following are roles of the porous partition in a galvanic cell, except ..........

1. A Neutralizing the ions produced by oxidation and reduction.
2. B Reacting with the ions of the two half-cell solutions.
3. C Connecting the two half-cell solutions indirectly.
4. D Keeping the oxidation and reduction reactions going.

Which of the following solutions affects the emf of the cell when it is used in the salt bridge of a Daniell cell?

1. A K₂SO₄
2. B NaNO₃
3. C KNO₃
4. D Na₂CO₃

A galvanic cell whose two half-cell electrolytes contain (SO₄²⁻), and whose salt bridge contains a cation of the fifth analytical group.
What happens after this cell has worked for some time?

1. A [SO₄²⁻] decreases in the cathode half-cell.
2. B The bridge cations move to the negative half-cell.
3. C The emf of the cell increases.
4. D The colour of the positive half-cell electrolyte deepens.

A single half-cell ..........

1. A is an open circuit, as no electrons flow from or to it.
2. B has only oxidation taking place on the surface of the electrode dipped in it.
3. C has only reduction taking place on the surface of the electrode dipped in it.
4. D always has an electrode reduction potential equal to zero.

All of the following are components of the standard hydrogen electrode, except ..........

1. A H⁺ ions
2. B H₂ gas
3. C H atoms
4. D Pt plate

From the opposite reduction potential of iron(II) ions: Fe²⁺(aq) + 2e⁻ → Fe(s) E° = –0.44 V
What is the emf of the reaction: Fe(s) + 2H⁺(aq) → H₂(g) + Fe²⁺(aq)?

1. A –0.22 V
2. B –0.44 V
3. C +0.22 V
4. D +0.44 V

A galvanic cell is represented by the following equation: 2M⁺(aq) + H₂(g) → 2M(s) + 2H⁺(aq) emf = +0.8 V
What is the standard oxidation potential of electrode (M)?

1. A –0.2 V
2. B +0.4 V
3. C –0.8 V
4. D +0.8 V

Which of the following solutions turns blue when copper turnings are added to it?

1. A AgNO₃
2. B Zn(NO₃)₂
3. C Ba(NO₃)₂
4. D NaNO₃

The opposite equation: Fe(s) + CuCl₂(aq) → Cu(s) + FeCl₂(aq) represents a reaction that is ..........

1. A spontaneous, in which the colour of the solution used changes with time.
2. B non-spontaneous, in which the mass of Cu increases with time.
3. C spontaneous, in which the mass of Fe increases with time.
4. D non-spontaneous, in which the mass of Fe decreases with time.

From the opposite figure:
What happens when the cell works?

1. A Ag⁺ ions in the solution increase.
2. B The copper electrode loses electrons.
3. C Electrons move through the electrolyte.
4. D The mass of the copper electrode increases.

The E°cell of a galvanic cell is calculated from the relation: E°cell = E°(1) – E°(2)
Which of the following represents (1) and (2)?

1. A (1): reduction potential of H⁺ , (2): reduction potential of Cu²⁺
2. B (1): oxidation potential of H₂ , (2): oxidation potential of Fe
3. C (1): oxidation potential of Fe , (2): oxidation potential of Au
4. D (1): reduction potential of Cu²⁺ , (2): reduction potential of Pt²⁺

From the opposite table: the standard reduction potential E° of the half-cell:
Cu²⁺/Cu : +0.34 V , Fe³⁺/Fe²⁺ : +0.77 V , Al³⁺/Al : –1.66 V , Zn²⁺/Zn : –0.76 V , Ag⁺/Ag : +0.8 V
Which pair of the following half-cells forms a cell whose E°cell equals + 0.43 V?

1. A Cu²⁺/Cu , Zn²⁺/Zn
2. B Al³⁺/Al , Zn²⁺/Zn
3. C Fe³⁺/Fe²⁺ , Cu²⁺/Cu
4. D Ag⁺/Ag , Cu²⁺/Cu

The two opposite equations represent the reduction potentials of the two halves of a galvanic cell.
• Cr³⁺(aq) + 3e⁻ → Cr(s) E° = –0.727 V
• Br₂(l) + 2e⁻ → 2Br⁻(aq) E° = +1.09 V
What is the emf of this galvanic cell?

1. A 1.817 V
2. B 0.363 V
3. C 4.724 V
4. D 1.316 V

From the galvanic cells shown in the following table:
Cell (1): anode Ga , cathode Pd , E°cell = +1.18 V
Cell (2): anode Ga , cathode Cd , E°cell = +0.16 V
Cell (3): anode Cd , cathode Pd , E°cell = ?
What is the E°cell of cell (3)?

1. A –1.34 V
2. B –1.02 V
3. C +1.02 V
4. D +1.34 V

Metal (X) displaces the hydrogen of HCl acid, while metal (Y) cannot. If the emf of the cell made of the two half-cells (X) and (Y) is 2.46 V and the reduction potential of electrode (Y) is 0.8 V,
then the reduction potential of electrode (X) is ..........

1. A +1.66 V
2. B –3.26 V
3. C +3.26 V
4. D –1.66 V

The value of the standard hydrogen potential changes when each of the following is used, except ..........

1. A (1 M) H₂SO₄
2. B (0.5 M) H₂SO₄
3. C (0.5 M) HCl
4. D (1.5 M) HCl

A galvanic cell is made of the standard zinc half-cell and the standard hydrogen half-cell.
Which of the following describes this cell after it has worked for some time?

1. A The pH around the hydrogen electrode decreases.
2. B The pOH around the hydrogen electrode decreases.
3. C [OH⁻] does not change in the hydrogen half-cell.
4. D [H⁺] does not change in the hydrogen half-cell.

The following two figures represent two galvanic cells in which the standard hydrogen electrode is used:
What role does the standard hydrogen electrode play in each of cells (1) and (2)?

1. A (1): cathode half-cell , (2): cathode half-cell.
2. B (1): anode half-cell , (2): cathode half-cell.
3. C (1): cathode half-cell , (2): anode half-cell.
4. D (1): anode half-cell , (2): anode half-cell.

From the standard potentials of the opposite half-cells:
2H⁺(aq) + 2e⁻ → H₂(g) E° = 0
K⁺(aq) + e⁻ → K(s) E° = –2.93 V
F₂(g) + 2e⁻ → 2F⁻(aq) E° = +2.87 V
Al³⁺(aq) + 3e⁻ → Al(s) E° = –1.66 V
Which of the following is the strongest reducing agent?

1. A H⁺(aq)
2. B K(s)
3. C F⁻(aq)
4. D Al(s)

In the half-cell: X²⁺ + 2e⁻ → X E° = –0.13 V it can be concluded that ..........

1. A (X): does not displace the hydrogen of acids.
2. B (X): is a reducing agent.
3. C (X²⁺): is a reducing agent.
4. D (X): is an oxidizing agent.

From the opposite standard potentials:
Ag⁺ + e⁻ → Ag E° = +0.8 V
Ni²⁺ + 2e⁻ → Ni E° = –0.25 V
When the two opposite half-cells are used to make a galvanic cell, ..........

1. A Ag⁺ is an oxidizing agent, while Ni²⁺ is a reducing agent.
2. B Ni²⁺ can be reduced by silver metal.
3. C Ni²⁺ is a stronger oxidizing agent than Ag⁺
4. D Ni is a stronger reducing agent than Ag

From the opposite spontaneous redox reactions:
(1) X + Y → X⁻ + Y⁺
(2) Y⁺ + Z → Y + Z⁺
(3) Z + X → Z⁺ + X⁻
The correct order of the strength of the oxidizing agents is ..........

1. A X⁻ < Y < Z
2. B Z < Y < X⁻
3. C Z < Y⁺ < X
4. D X < Y⁺ < Z

Four metals (A), (B), (C) and (D) have the following properties:
• Only metals (A) and (C) can react with HCl acid.
• Metal (C) reacts with the salt solutions of all the other metals.
• Metal (D) reacts with the cations of metal (B).
Which of the following represents the strength of these metals as reducing agents?

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

From the opposite table:
I₂(s) + 2e⁻ → 2I⁻(aq) E° = +0.535 V
Cu²⁺(aq) + 2e⁻ → Cu(s) E° = +0.34 V
2H⁺(aq) + 2e⁻ → H₂(g) E° = 0 V
Fe²⁺(aq) + 2e⁻ → Fe(s) E° = –0.409 V
Zn²⁺(aq) + 2e⁻ → Zn(s) E° = –0.762 V
Which of the following is correct?

1. A I₂(s) is the strongest oxidizing agent and Zn(s) the strongest reducing agent
2. B Zn(s) can reduce I₂(s) and Fe²⁺(aq)
3. C Cu(s) can oxidize Zn(s) and Fe²⁺(aq)
4. D Fe(s) can oxidize Cu(s) and Zn²⁺(aq)

From the opposite table: A²⁺/A : E° = –1.029 V , B⁺/B : E° = +0.8 V
What happens when a rod of metal (A) is dipped in a 1 M aqueous solution of (B⁺) ions?

1. A (B) gradually dissolves.
2. B (B) is deposited on (A).
3. C No reaction takes place.
4. D Water decomposes into H₂ and O₂

From the opposite table:
Cr³⁺/Cr²⁺ : E° = –0.41 V , Mn³⁺/Mn²⁺ : E° = +1.57 V
Fe³⁺/Fe²⁺ : E° = +0.77 V , Co³⁺/Co²⁺ : E° = +1.97 V
Which of the following shows the correct order of the ease with which the ion changes from oxidation state (+2) to oxidation state (+3)?

1. A Co²⁺ < Mn²⁺ < Fe²⁺ < Cr²⁺
2. B Cr²⁺ < Fe²⁺ < Mn²⁺ < Co²⁺
3. C Mn²⁺ < Co²⁺ < Fe²⁺ < Cr²⁺
4. D Cr²⁺ < Co²⁺ < Mn²⁺ < Fe²⁺

From the opposite table and the following equation: Mn³⁺ + e⁻ → Mn²⁺ E° = –1.029 V
Pb²⁺ + 2e⁻ → Pb E° = –0.126 V , Fe²⁺ + 2e⁻ → Fe E° = –0.409 V
Mg²⁺ + 2e⁻ → Mg E° = –2.375 V , Zn²⁺ + 2e⁻ → Zn E° = –0.762 V
Which of the following can reduce the Mn³⁺ ion to the Mn²⁺ ion?

1. A Mg only.
2. B Zn only.
3. C Fe and Pb only.
4. D Zn , Fe and Pb

From the opposite table:
Mn⁷⁺(aq) + 5e⁻ → Mn²⁺(aq) E° = +1.51 V
Zn²⁺(aq) + 2e⁻ → Zn(s) E° = –0.76 V
Ag⁺(aq) + e⁻ → Ag(s) E° = +0.8 V
Au⁺(aq) + e⁻ → Au(s) E° = +1.69 V
Which of the following metals can be oxidized using the MnO₄⁻ ion?

1. A Zn and Ag only
2. B Ag and Au only
3. C Zn and Au only
4. D Zn , Ag and Au

The following equations represent three electrochemical processes:
(1) Fe(s) + Ni²⁺(aq) → Fe²⁺(aq) + Ni(s)
(2) Ni(s) + Pb²⁺(aq) → Ni²⁺(aq) + Pb(s)
(3) Pb(s) + Fe²⁺(aq) → Pb²⁺(aq) + Fe(s)
and the standard reduction potentials: Pb²⁺/Pb : –0.13 V , Ni²⁺/Ni : –0.25 V , Fe²⁺/Fe : –0.44 V
Which of the following represents the spontaneous processes?

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

From the following two cells:
Which of the following is correct?

1. A Cu : (R) , Ag : (Q) , Zn : (P)
2. B Cu : (R) , Zn : (Q) , Ag : (P)
3. C Ag : (R) , Zn : (Q) , Cu : (P)
4. D Ag : (R) , Cu : (Q) , Zn : (P)

The circuit shown in the opposite figure is used to compare the activity of four unknown metals (X), (Q), (Y) and (Z), and the following table shows the voltmeter readings in the four cases:
Metal (X): direction of electron flow in the external circuit X → Cu , voltmeter reading +0.87 V
Metal (Q): direction of electron flow Cu → Q , voltmeter reading +1.2 V
Metal (Y): direction of electron flow Y → Cu , voltmeter reading +1.58 V
Metal (Z): direction of electron flow Z → Cu , voltmeter reading +0.36 V
Which of the following shows the order of activity of these metals?

1. A Z < Y < Q < X
2. B Q < Y < X < Z
3. C Q < Z < X < Y
4. D X < Q < Z < Y

An excess of zinc powder was added to a small volume of a mixture of magnesium nitrate and copper(II) chloride solutions.
Which cations are present in the reaction mixture after the reaction ends?

1. A Mg²⁺ , Cu²⁺
2. B Zn²⁺ , Cu²⁺
3. C Zn²⁺ , Mg²⁺
4. D Cu²⁺ , Zn²⁺ , Mg²⁺

The following figure represents three experiments done to find the chemical activity of three metals (X), (Y) and (Z):
• Metal (X) in Z²⁺ solution: no reaction.
• Metal (X) in Y²⁺ solution: metal (Y) is deposited on metal (X).
• Metal (Z) in Y²⁺ solution: metal (Y) is deposited on metal (Z).
Which of the following represents the order of activity of these metals?

1. A Y < Z < X
2. B Z < X < Y
3. C X < Y < Z
4. D Y < X < Z

Which of the following is correct as a result of placing an iron rod in CuSO₄ solution for some time?

1. A Mass of iron: decreases , [Cu²⁺]: decreases , number of moles of ions: decreases
2. B Mass of iron: increases , [Cu²⁺]: increases , number of moles of ions: decreases
3. C Mass of iron: decreases , [Cu²⁺]: decreases , number of moles of ions: does not change
4. D Mass of iron: increases , [Cu²⁺]: increases , number of moles of ions: does not change

When a rod of metal (A) was dipped in a concentrated aqueous solution (B), the solution turned blue, and when NaCl(aq) was added to solution (B), precipitate (C) formed, which dissolves when concentrated ammonia solution is added to it.
Which of the following is correct?

1. A Fe : (A) , Zn(NO₃)₂ : (B) , ZnCl₂ : (C)
2. B Cu : (A) , AgNO₃ : (B) , AgCl : (C)
3. C Ni : (A) , Al(NO₃)₃ : (B) , AlCl₃ : (C)
4. D Co : (A) , Pb(NO₃)₂ : (B) , PbCl₂ : (C)

The following table shows whether 5 different metals (A), (B), (C), (D) and (E) react with solutions of their nitrates (✓ reaction takes place, ✗ no reaction):
A(NO₃)₂ solution: metals (B) ✓ , (C) ✓ , (D) ✗ , (E) ✓
B(NO₃)₂ solution: metals (A) ✗ , (C) ✗ , (D) ✗ , (E) ✗
C(NO₃)₂ solution: metals (A) ✗ , (B) ✓ , (D) ✗ , (E) ✗
DNO₃ solution: metals (A) ✓ , (B) ✓ , (C) ✓ , (E) ✓
E(NO₃)₂ solution: metals (A) ✗ , (B) ✓ , (C) ✓ , (D) ✗
What is the correct order of the chemical activity of these elements?

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

The following table shows the results of adding 6 g of nickel to four solutions of the salts of metals (W), (X), (Y) and (Z), of the same volume and concentration, for a fixed time:
Salt solution of metal (W): mass of nickel after 15 min = 5 g
Salt solution of metal (X): mass of nickel after 15 min = 5.5 g
Salt solution of metal (Y): mass of nickel after 15 min = 4.5 g
Salt solution of metal (Z): mass of nickel after 15 min = 0
Which of the following is correct?

1. A Metal (W) comes before metal (X) in the electrochemical series.
2. B Metal (Y) can displace metal (Z) from its salt solution.
3. C Metal (Y) comes before nickel in the electrochemical series.
4. D Metal (Z) is nickel(II) chloride solution.

The reaction of zinc sulphite with hydrochloric acid is represented by the following ionic equation:
ZnSO₃(s) + 2H⁺(aq) → Zn²⁺(aq) + SO₂(g) + H₂O(l)
(1) Is this reaction a redox reaction? Explain.
(2) What is the effect of passing the gas produced on the colour of a (H⁺ + Cr₂O₇²⁻) solution?

The two experiments shown in the following figures were done using two zinc plates:
(1) Is the reaction in experiment (1) complete or reversible? Explain.
(2) State two changes in experiment (2) that show that oxidation and reduction took place.

A galvanic cell in which the electrolyte of the first half-cell contains Ag⁺(aq) ions and the second half contains Ni²⁺(aq) ions:
(1) Deduce the ionic equation of the overall reaction in this cell, with explanation.
(2) Calculate the emf of this cell, given the following two oxidation potentials:
Ni → Ni²⁺ + 2e⁻ E° = +0.23 V
Ag → Ag⁺ + e⁻ E° = –0.8 V

The following ionic equation represents the overall reaction in a galvanic cell:
H₂(g) + Cu²⁺(aq) → 2H⁺(aq) + Cu(s)
(1) What is the oxidizing agent in this reaction? Explain.
(2) Calculate the emf of this cell.

• Metal (A): monovalent, its oxidation potential is +0.7 V
• Metal (B): divalent, its oxidation potential is –0.4 V
(1) Calculate the emf of the galvanic cell made of them.
(2) Write the equation of the overall reaction in this cell.

From the opposite electrochemical potentials:
A⁴⁺(aq) + e⁻ → A³⁺(aq) E° = 0.01 V
B³⁺(aq) + e⁻ → B²⁺(aq) E° = 0.77 V
Show whether the following reaction is spontaneous, with explanation:
A⁴⁺(aq) + B²⁺(aq) → A³⁺(aq) + B³⁺(aq)

From the opposite figure:
(1) Does magnesium act as the cathode or the anode in this cell? Explain your answer.
(2) State two of the changes that happen when the Mg rod is replaced by a Ag rod in this cell.

The opposite figure represents a galvanic cell. Given that the oxidation potential of cadmium is 0.4 V and that of copper is –0.34 V:
(1) State the number that shows each of:
(a) the direction of electron movement.
(b) the direction of anion movement.
(2) Write the equation of the overall reaction.

From the following substances: nickel, aluminium, silver, Ni(NO₃)₂(aq), Al(NO₃)₃(aq), AgNO₃(aq)
Replace the numbers shown on the opposite figure with the suitable substances from the list above to give the largest voltmeter reading, and calculate this reading using the electrochemical potentials.

From the following table:
Metal (A): reduction potential –1.66 V
Metal (B): reduction potential +0.34 V
Metal (C): reduction potential –0.44 V
Metal (D): reduction potential –2.73 V
Metal (E): reduction potential –0.76 V
Arrange these metals according to their ability to displace one another from solutions of their salts, with explanation.

The experiments shown in the following figures were done to compare the chemical activity of four metals; all of them were accompanied by a chemical change:
(1) What change happens with time in experiment (1) to each of the following, giving the reason:
(a) rod (X). (b) the solution of Cu²⁺ ions
(2) Arrange the four metals in these experiments in ascending order of chemical activity.

The following figures represent three different experiments:
Two galvanic cells can be made by connecting:
• metal (P) with metal (R).
• metal (P) with metal (Q).
State the role of metal (P) in each cell, with explanation.

Dilute hydrochloric acid was added to three tubes containing iron, copper and magnesium metals, each separately, and the amounts of hydrogen given off with each metal were plotted as the curves shown in the opposite figure.
Match each metal with the curve that represents it, explaining your answer.

A few drops of Na₂S solution were added to the cathode half-cell of a Daniell cell. Which of the following is correct?

1. A The electromotive force increases.
2. B The life time of the cell decreases.
3. C The concentration of Cu²⁺ cations increases.
4. D The current reverses and the emf decreases.

In the following reaction:
5Cl⁻ + 8H⁺ + MnO₄⁻ → (5/2) Cl₂ + 4H₂O + Mn²⁺
(Cl₂ / 2Cl⁻ = +1.36 V , Mn²⁺ / Mn⁷⁺ = –1.52 V)
Which of the following gives the type and the potential of the reaction, respectively?

1. A Spontaneous, and the potential = +0.16 V
2. B Non-spontaneous, and the potential = –2.88 V
3. C Spontaneous, and the potential = –0.16 V
4. D Non-spontaneous, and the potential = +2.88 V

The opposite table shows the components of two galvanic cells and the standard potential of each:
Cell 1: anode (X) , cathode Ag , emf = 0.80 V
Cell 2: anode (Y) , cathode Ag , emf = 1.56 V
If a galvanic cell is made with electrodes (X , Y), its emf equals ...........

1. A +2.36 V
2. B –2.36 V
3. C +0.76 V
4. D –0.76 V

The following figure shows two galvanic cells:
Which of the following is correct for electrodes (A , B , C)?

1. A The strongest reducing agent is (A).
2. B The lowest oxidation potential is (C).
3. C The least active electrode is (B).
4. D The mass of electrode (C) increases.

In a galvanic cell made of electrodes (X) and (Y), electrons were observed to flow towards electrode (Y) while the cell works. Which of the following is correct?

1. A The reduction potential of (X) is smaller than that of (Y).
2. B The oxidation potential of (X) is smaller than that of (Y).
3. C Electrode (X) is the positive electrode of the cell.
4. D Anions flow through the bridge towards electrode (Y).

The standard potentials of electrodes (X) and (Y) are as follows:
X(s) + 2H⁺(1 M) → X²⁺(aq) + H₂(g) E° = +0.76 V
Y(s) + 3H⁺(1 M) → Y³⁺(aq) + (3/2) H₂(g) E° = +1.66 V
Which of the following is correct when an electrochemical cell is made from electrodes (X) and (Y)?

1. A The anode is (X) and the emf equals +0.9 V
2. B The anode is (Y) and the emf equals +0.9 V
3. C The anode is (X) and the emf equals +2.42 V
4. D The anode is (Y) and the emf equals +2.42 V

From the electric cells shown:
Which of the following describes the cell made of electrode (B) as anode and (A) as cathode?

1. A emf = +2 V , a spontaneous reaction takes place in it
2. B emf = –1.2 V , a non-spontaneous reaction takes place in it
3. C emf = –2 V , a non-spontaneous reaction takes place in it
4. D emf = +1.2 V , a spontaneous reaction takes place in it

In the following spontaneous reaction:
Ni(s) + CuCl₂(aq) → Cu(s) + NiCl₂(aq)
Which of the following is correct?

1. A The copper ion is a strong reducing agent.
2. B Solutions of copper salts can be kept in nickel containers.
3. C Solutions of nickel salts can be kept in a copper container.
4. D The chloride ion is a strong oxidizing agent.

Which of the following reactions can represent a spontaneous reaction inside an electric cell?

1. A Cu(s) + Zn²⁺(aq) → Cu²⁺(aq) + Zn(s)
2. B Mg(s) + Zn²⁺(aq) → Mg²⁺(aq) + Zn(s)
3. C 2Ag(s) + Cu²⁺(aq) → 2Ag⁺(aq) + Cu(s)
4. D 3Cu(s) + 2Al³⁺(aq) → 3Cu²⁺(aq) + 2Al(s)

When a galvanic cell was made from electrodes (X) and (Y), the concentration of Y²⁺ ions was observed to increase. Which of the following statements is correct?

1. A The oxidation potential of (X) is greater than that of (Y).
2. B Y²⁺ is a reducing agent while the cell works.
3. C Electrons flow in the wire from (X) to (Y).
4. D X²⁺ is an oxidizing agent while the cell works.

Using the opposite table:
Cd + Zn²⁺ → Cd²⁺ + Zn non-spontaneous
Cd + Cu²⁺ → Cd²⁺ + Cu spontaneous
Which of the following gives the correct order of the opposite metal ions by their strength as oxidizing agents?

1. A Cd²⁺ > Cu²⁺ > Zn²⁺
2. B Zn²⁺ > Cu²⁺ > Cd²⁺
3. C Cd²⁺ > Zn²⁺ > Cu²⁺
4. D Cu²⁺ > Cd²⁺ > Zn²⁺

From the following figures:
Which of the following gives the electrodes that form a galvanic cell with the greatest electromotive force?

1. A (Z) , (X).
2. B (Y) , H₂.
3. C (Y) , (X).
4. D (Z) , (Y).

The following reaction takes place inside an electrochemical cell:
3Cu²⁺ + 2Cr → 3Cu + 2Cr³⁺
Given that: (Cu²⁺ + 2e⁻ → Cu , E° = +0.340 V , Cr → Cr³⁺ + 3e⁻ , E° = +0.740 V)
Which of the following gives the type of the cell and its emf?

1. A Galvanic , emf = +1.08 V
2. B Electrolytic , emf = –1.08 V
3. C Galvanic , emf = +0.4 V
4. D Electrolytic , emf = –0.4 V

From the following figures:
Which of the following is correct?

1. A When (1) is connected to (4) by a salt bridge and an external wire, (4) becomes the anode and (1) the cathode.
2. B A spontaneous reaction takes place in (2) and the concentration of copper ions increases.
3. C When (1) is connected to (4) by a salt bridge and a wire, electrons move spontaneously from (1) to (4).
4. D A spontaneous reaction takes place in vessel (3) and the concentration of zinc ions decreases.

A galvanic cell consists of:
• electrode (X) dipped in XSO₄ solution
• electrode (Y) dipped in YSO₄ solution
If metal (X) is a stronger reducing agent than (Y), which of the following describes what happens in this cell?

1. A Electrons move from (Y) to (X) through the external wire.
2. B The mass of electrode (X) increases with time.
3. C Negative ions move from the bridge to half-cell (X).
4. D (X²⁺) ions are reduced at the anode.

An electric cell in which the following reaction takes place: 2Y(s) + 3X²⁺(aq) → 2Y³⁺(aq) + 3X(s) , emf = +1.6 V
Which of the following is correct for both the type of electrode (Y) and the type of this cell?

1. A Electrode (Y): cathode / cell type: galvanic
2. B Electrode (Y): anode / cell type: electrolytic
3. C Electrode (Y): anode / cell type: galvanic
4. D Electrode (Y): cathode / cell type: electrolytic

Four electrodes (X), (Y), (Z) and (L), where:
X²⁺/X : –0.44 V , Y²⁺/Y : +1.5 V , Z/Z²⁺ : –0.34 V , L/L²⁺ : +1.18 V
Which of the following reactions represents a cell that produces the greatest electromotive force (emf)?

1. A Y + L²⁺ → Y²⁺ + L
2. B X + L²⁺ → X²⁺ + L
3. C L + Y²⁺ → L²⁺ + Y
4. D X + Y²⁺ → X²⁺ + Y

The opposite figure shows a galvanic cell made of electrodes (X , Y). Which of the following represents the overall cell reaction?

1. A X(s) + Y³⁺(aq) → X²⁺(aq) + Y(s)
2. B Y(s) + X²⁺(aq) → Y³⁺(aq) + X(s)
3. C 2X(s) + 3Y³⁺(aq) → 2X²⁺(aq) + 3Y(s)
4. D 3X(s) + 2Y³⁺(aq) → 3X²⁺(aq) + 2Y(s)

Which of the following reactions represents a non-spontaneous reaction at the anode of an electrolytic cell?

1. A Br₂ + 2e⁻ → 2Br⁻
2. B Cu²⁺(aq) → Cu(s) + 2e⁻
3. C 4OH⁻(aq) → O₂(g) + 2H₂O(l) + 4e⁻
4. D 2H₂O(l) + 2e⁻ → H₂(g) + 4OH⁻(aq)

Galvanic cell (X) is made of electrodes (A , B), and electrons move in the external wire from (B) to (A). Electric cell (Y), made of the same electrodes, has the following reaction: A(s) + B²⁺(aq) → A²⁺(aq) + B(s)
Which of the following choices describes cell (Y)?

1. A Galvanic with positive emf, electrode (A) is negative.
2. B Galvanic with positive emf, electrode (B) is positive.
3. C Electrolytic with negative emf, electrode (A) is negative.
4. D Electrolytic with negative emf, electrode (B) is negative.

Two galvanic cells:
• First cell: electrode (X) is the anode and the hydrogen electrode is the cathode, and it gives an emf of +0.23 V
• Second cell: electrode (Y) is the cathode and the hydrogen electrode is the anode, and it gives an emf of +0.8 V
Which of the following describes the cell made of electrodes (X) and (Y)?

1. A (X) anode and (Y) cathode , emf = 1.03 V
2. B (X) anode and (Y) cathode , emf = 0.57 V
3. C (Y) anode and (X) cathode , emf = 1.03 V
4. D (Y) anode and (X) cathode , emf = 0.57 V

A galvanic cell made of iron and tin electrodes:
Fe(s) → Fe²⁺(aq) + 2e⁻ E° = +0.409 V
Sn²⁺(aq) + 2e⁻ → Sn(s) E° = +0.150 V
Which of the following gives the anode or cathode and the emf of the cell?

1. A The iron electrode is the anode and the emf of the cell is +0.559 V
2. B The iron electrode is the cathode and the emf of the cell is –0.559 V
3. C The tin electrode is the anode and the emf of the cell is +0.259 V
4. D The tin electrode is the cathode and the emf of the cell is –0.259 V

The following reaction represents an electrochemical cell:
X(s) + 2Y⁺(aq) → X²⁺(aq) + 2Y(s)
Given that:
X(s) → X²⁺(aq) + 2e⁻ E° = 0.23 V
Y⁺ + e⁻ → Y(s) E° = 0.8 V
Which of the following gives the type of the cell and its emf?

1. A Electrolytic and emf = –1.03 V
2. B Galvanic and emf = –0.564 V
3. C Electrolytic and emf = +0.564 V
4. D Galvanic and emf = +1.03 V

The following reaction represents a galvanic cell: Fe(s) + Pb²⁺(aq) → Fe²⁺(aq) + Pb(s)
Which of the following can be used as the electrolyte solution in the salt bridge of this cell?

1. A Sodium chloride.
2. B Sodium carbonate.
3. C Sodium nitrate.
4. D Ethyl alcohol.

The following equation represents the reaction in an electric cell:
2X + 3CuSO₄ → X₂(SO₄)₃ + 3Cu , E_cell = +1.8 V
Which of the following gives the reduction potential of (X)? (Cu → Cu²⁺ + 2e⁻ , E° = –0.34 V)

1. A –2.14 V
2. B +1.46 V
3. C +2.14 V
4. D –1.46 V

The opposite table shows the oxidation potentials of some electrodes:
X : 0.76 , Y : –0.34 , Z : 1.67 , W : 2.37 , E : –0.8
An electric cell was made of electrodes (X , Y). Which of the following changes to this cell increases the electromotive force and changes the direction of the current?

1. A Replacing the anode with electrode W
2. B Replacing the anode with electrode Z
3. C Replacing the cathode with electrode W
4. D Replacing the cathode with electrode E

The following table shows the standard electrode potentials of four elements:
A²⁺ + 2e⁻ → A E° = –2.71 V
B → B²⁺ + 2e⁻ E° = +0.40 V
C²⁺ + 2e⁻ → C E° = +0.80 V
D → D²⁺ + 2e⁻ E° = –1.20 V
Which of the following gives the number of galvanic cells that can be made from these elements, and the highest emf that can be obtained?

1. A 4 cells , emf = 3.91 V
2. B 6 cells , emf = 3.91 V
3. C 6 cells , emf = 3.11 V
4. D 12 cells , emf = 3.51 V

The following reaction takes place in an electric cell:
2M(s) + 3Zn²⁺(aq) → 2M³⁺(aq) + 3Zn(s) , E°_cell = +1 V
Given that: Zn²⁺(aq) → Zn(s) E° = –0.76 V
Which of the following gives the type of electrode (M), its oxidation potential and the type of the cell?

1. A Electrode (M) is the anode, its oxidation potential = +1.76 and the cell is galvanic.
2. B Electrode (M) is the anode, its oxidation potential = +0.24 and the cell is electrolytic.
3. C Electrode (M) is the cathode, its oxidation potential = –0.24 and the cell is electrolytic.
4. D Electrode (M) is the cathode, its oxidation potential = –1.76 and the cell is galvanic.

From the opposite electrode potentials:
X²⁺ + 2e⁻ → X E° = –0.41 V
Y → Y²⁺ + 2e⁻ E° = –0.23 V
Which of the following choices describes the reaction: X + Y²⁺ → X²⁺ + Y?

1. A Non-spontaneous, and the mass of electrode (X) decreases.
2. B Non-spontaneous, and the mass of electrode (Y) decreases.
3. C Spontaneous, and the mass of electrode (X) decreases.
4. D Spontaneous, and the mass of electrode (Y) decreases.

The following table shows the potentials of some elements:
X → X²⁺ E° = 0.76
W → W²⁺ E° = 2.37
Z²⁺ → Z E° = 0.23
When two of the electrodes above are used to make a cell with an emf of 1.61 V, which of the following describes the change when the cathode of this cell is replaced with the third electrode?

1. A The emf increases and the direction of the current stays the same.
2. B The emf decreases and the direction of the current stays the same.
3. C The emf increases and the direction of the current reverses.
4. D The emf decreases and the direction of the current reverses.

The following reaction represents an electrochemical cell: X²⁺(aq) + 2Y(s) → X(s) + 2Y⁺(aq)
If:
X²⁺(aq) → X(s) E° = –0.56 V
Y⁺(aq) → Y(s) E° = +0.23 V
which of the following gives the type of the cell and its electromotive force (emf)?

1. A Galvanic , emf = +0.23 V
2. B Galvanic , emf = +0.79 V
3. C Electrolytic , emf = –0.23 V
4. D Electrolytic , emf = –0.79 V

From the opposite standard potentials:
X²⁺ + 2e⁻ → X E° = –0.402 V
Y → Y²⁺ + 2e⁻ E° = –0.23 V
Which of the following choices describes the following reaction? Y + X²⁺ → Y²⁺ + X

1. A Non-spontaneous, and the mass of (X) decreases.
2. B Non-spontaneous, and electrode (Y) is the anode.
3. C Spontaneous, and electrode (Y) is the anode.
4. D Spontaneous, and the mass of (X) decreases.

The following table shows the potentials of some metals:
Al : –1.67 V , Ag : 0.8 V , Zn : –0.76 V , Cu : 0.34 V , Fe : –0.409 V
When equal masses of iron pieces are placed in several solutions of equal concentration of copper sulphate, aluminium sulphate, zinc sulphate and silver nitrate, which of the following choices is correct about the corrosion of the iron pieces in these solutions?

1. A In zinc sulphate it is slower than in aluminium sulphate.
2. B In copper sulphate it is faster than in silver nitrate.
3. C In silver nitrate it is faster than in copper sulphate.
4. D In aluminium sulphate it is slower than in zinc sulphate.

When a magnesium ribbon is placed in silver nitrate solution, the following reaction takes place:
Mg(s) + 2AgNO₃(aq) → Mg(NO₃)₂(aq) + 2Ag(s)
Which of the following choices correctly describes what happened?

1. A Oxidation of magnesium and reduction of silver ions.
2. B Oxidation of magnesium and oxidation of silver.
3. C Reduction of magnesium and oxidation of silver.
4. D Reduction of magnesium and reduction of silver ions.

When potassium dichromate solution acidified with sulphuric acid is added to iron(II) sulphate solution, the correct equation for the redox reaction that takes place is ..........

1. A Fe²⁺(aq) + Cr₂O₇²⁻(aq) + 14H⁺(aq) → Fe³⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)
2. B 6Fe²⁺(aq) + Cr₂O₇⁻(aq) + 14H⁺(aq) → 6Fe³⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)
3. C Fe²⁺(aq) + Cr₂O₇⁻(aq) + 14H⁺(aq) → Fe³⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)
4. D 6Fe²⁺(aq) + Cr₂O₇²⁻(aq) + 14H⁺(aq) → 6Fe³⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)

From the cell shown, which of the following is correct?

1. A The cell is galvanic and the concentration of solution (A) increases.
2. B The cell is galvanic and the concentration of solution (B) increases.
3. C The cell is electrolytic and the concentration of solution (A) decreases.
4. D The cell is electrolytic and the concentration of solution (B) decreases.

The opposite reaction takes place in an electrochemical cell: Sn(s) + 2Ag⁺(aq) → Sn²⁺(aq) + 2Ag(s)
The reaction represents ..........

1. A a galvanic cell; electrons move from Ag to Sn
2. B an electrolytic cell; electrons move from Sn²⁺ to Ag
3. C an electrolytic cell; electrons move from Ag⁺ to Sn
4. D a galvanic cell; electrons move from Sn to Ag⁺

Which of the following changes increases the working time of the galvanic cell made of silver and nickel half-cells?

1. A Increasing the concentration of silver ions in the cathode half-cell.
2. B Decreasing the concentration of nickel ions in the anode half-cell.
3. C Decreasing the mass of the anode.
4. D Increasing the mass of the cathode.

In the galvanic cell whose reaction is represented by the ionic equation: Zn(s) + Pb²⁺(aq) → Zn²⁺(aq) + Pb(s)
When drops of HCl(aq) are added to each half-cell, which of the following is correct?

1. A The concentration of Pb²⁺(aq) ions increases.
2. B The emf of the cell increases.
3. C The life time of the battery decreases.
4. D The concentration of Zn²⁺(aq) ions decreases.

When metal (X) was placed in a solution of the salt YCl₂, the concentration of Y²⁺ cations changed from 0.1 M to 0.01 M. Which of the following is present in the solution?

1. A Cl⁻ , Y²⁺ and X²⁺ ions
2. B Cl⁻ and X²⁺ ions only.
3. C Cl⁻ and Y²⁺ ions, and (X) settles at the bottom of the vessel.
4. D Cl⁻ ions, and (X) and (Y) settle at the bottom of the vessel.

Three rods of different elements (A , B , C) were placed in dilute HCl acid. (A , B) reacted and element (C) did not react. When element (A) was placed in a solution containing ions of element (B), it corroded. The order of these elements by their oxidation potentials is ..........

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

A rod of element (A) is placed in a solution of ions of element (B). Given that element (A) is divalent and element (B) is monovalent, which of the following is correct?

1. A The number of moles of (A) dissolved is twice the number of moles of (B) deposited.
2. B The number of moles of (A) dissolved is half the number of moles of (B) deposited.
3. C The number of moles of (A) dissolved equals the number of moles of (B) deposited.
4. D The number of moles of (A) dissolved is three times the number of moles of (B) deposited.

A piece of zinc was added to dilute sulphuric acid, then the gas produced was passed into four different solutions under the necessary conditions. Which of the following processes can take place?

1. A YSO₄ → Y₂(SO₄)₃
2. B WCl → WCl₂
3. C X₂(SO₄)₃ → XSO₄
4. D ZCl₂ → ZCl₃

In the opposite reaction: MnO₂(s) + 4HCl(aq) → MnCl₂(aq) + 2H₂O(l) + Cl₂(g)
the changes that take place are ..........

1. A Mn⁴⁺ → Mn²⁺ , Cl₂ → 2Cl⁻
2. B Mn⁴⁺ → Mn²⁺ , 2Cl⁻ → Cl₂
3. C Mn²⁺ → Mn⁴⁺ , 2Cl⁻ → Cl₂
4. D Mn²⁺ → Mn⁴⁺ , Cl₂ → 2Cl⁻

Given that the divalent element (X) comes before the monovalent element (Y) in the electrochemical series, the overall reaction in the galvanic cell made of them is ..........

1. A X²⁺ + 2Y⁺ → X + 2Y
2. B X + 2Y⁺ → X²⁺ + 2Y
3. C 2Y + X²⁺ → 2Y⁺ + X
4. D 2Y + X → 2Y⁺ + X²⁺

A galvanic cell is made of chromium and platinum electrodes. If the standard reduction potential of each is:
Cr³⁺(aq) + 3e⁻ → Cr(s) E° = –0.727 V
Pt²⁺(aq) + 2e⁻ → Pt(s) E° = +1.2 V
then the overall reaction in the cell is ..........

1. A 3Pt²⁺(aq) + 2Cr³⁺(aq) → 3Pt(s) + 2Cr(s)
2. B Pt²⁺(aq) + 2Cr(s) → Pt(s) + 2Cr³⁺(aq)
3. C Cr(s) + Pt²⁺(aq) → Cr³⁺(aq) + Pt(s)
4. D 2Cr(s) + 3Pt²⁺(aq) → 2Cr³⁺(aq) + 3Pt(s)

Given the potentials of the elements:
K⁺ → K E° = –2.92 V
Cu²⁺ → Cu E° = 0.34 V
the overall reaction of the galvanic cell made of the two electrodes is ..........

1. A 2K(s) + Cu²⁺(aq) → 2K⁺(aq) + Cu(s)
2. B Cu(s) + 2K(s) → Cu²⁺(aq) + 2K⁺(aq)
3. C Cu²⁺(aq) + 2K⁺(aq) → Cu(s) + 2K(s)
4. D K⁺(aq) + Cu(s) → K(s) + Cu²⁺(aq)

From the standard potentials of the two opposite half-cells:
Al → Al³⁺ + 3e⁻ E° = 1.67 V
Cu²⁺ + 2e⁻ → Cu E° = 0.34 V
What is the reaction in the galvanic cell made of them?

1. A Al + Cu²⁺ → Al³⁺ + Cu
2. B 3Cu + 2Al³⁺ → 3Cu²⁺ + 2Al
3. C 2Al + 3Cu²⁺ → 2Al³⁺ + 3Cu
4. D Cu²⁺ + Al³⁺ → Cu + Al

The following two figures represent two galvanic cells:
Given that (A) and (B) are divalent and (C) is trivalent, the overall reaction of the galvanic cell made of elements (A) and (C) is ..........

1. A 2C(s) + 3A²⁺(aq) → 2C³⁺(aq) + 3A(s)
2. B 3A(s) + 2C³⁺(aq) → 3A²⁺(aq) + 2C(s)
3. C 2A(s) + 3C²⁺(aq) → 2A³⁺(aq) + 3C(s)
4. D 3C(s) + 2A³⁺(aq) → 3C²⁺(aq) + 2A(s)

• The potential of a cell made of element (X) and the standard hydrogen electrode = 0.280 V
• The potential of a cell made of element (X) and element (Y) = 2.095 V
When element (Y) is placed in a solution of element (X), no reaction takes place.
Then the potential of the cell made of element (Y) and the standard hydrogen electrode equals ..........

1. A –2.375 V
2. B 2.375 V
3. C 1.815 V
4. D –1.815 V

Which of the following represents the reaction of the galvanic cell made of silver and manganese electrodes, and the reducing agent in it?

1. A Mn(s) + 2Ag⁺(aq) → Mn²⁺(aq) + 2Ag(s) , the reducing agent is Mn
2. B Ag(s) + Mn²⁺(aq) → Ag⁺(aq) + Mn(s) , the reducing agent is Ag
3. C Mn²⁺(aq) + Ag⁺(aq) → Mn(s) + Ag(s) , the reducing agent is Mn
4. D 2Ag⁺(aq) + Mn(s) → 2Ag(s) + Mn²⁺(aq) , the reducing agent is Ag

The standard potentials of the two opposite half-cells:
Fe(s) → Fe²⁺(aq) + 2e⁻ E° = +0.409 V
Ni²⁺(aq) + 2e⁻ → Ni(s) E° = –0.23 V
What is the emf of the galvanic cell made of them?

1. A 1.639 V
2. B 0.936 V
3. C 0.396 V
4. D 0.179 V

In the galvanic cell whose electrodes are nickel and cadmium, given that:
Cd(s) → Cd²⁺(aq) + 2e⁻ E° = +0.402 V
Ni²⁺(aq) + 2e⁻ → Ni(s) E° = –0.23 V
the emf of the cell is ..........

1. A 0.172 V
2. B –0.632 V
3. C 0.632 V
4. D –0.172 V

A cell made of elements (X) and (Y) has an emf of 0.94 V. Given that the standard oxidation potential of element (X) is 0.136 V and electrons move from (X) to (Y) through the wire, the oxidation potential of element (Y) equals ..........

1. A +0.8 V
2. B +1.076 V
3. C –0.8 V
4. D –1.076 V

A galvanic cell whose electrodes are tin and silver. Given that the standard reduction potential of tin = –0.136 V and of silver = +0.8 V, which of the following represents the spontaneous reduction reaction in the cell?

1. A 2Ag⁺(aq) + 2e⁻ → 2Ag(s) E° = +0.8 V
2. B 2Ag(s) → 2Ag⁺(aq) + 2e⁻ E° = –1.6 V
3. C 2Ag⁺(aq) + 2e⁻ → 2Ag(s) E° = –0.8 V
4. D 2Ag(s) → 2Ag⁺(aq) + 2e⁻ E° = +1.6 V

Given that:
A → A²⁺ + 2e⁻ E° = 0.409 V
B → B⁺ + e⁻ E° = –0.800 V
If a galvanic cell is made of elements (A) and (B), which of the following is correct?

1. A Anode reaction: A → A²⁺ , cathode reaction: 2B⁺ → 2B , E_cell = 1.209 V
2. B Anode reaction: 2B⁺ → 2B , cathode reaction: A → A²⁺ , E_cell = 1.4 V
3. C Anode reaction: B⁺ → B , cathode reaction: 2A → 2A²⁺ , E_cell = 0.896 V
4. D Anode reaction: 2A → 2A²⁺ , cathode reaction: B⁺ → B , E_cell = 0.879 V

Standard oxidation potentials (volts) of four elements: (A): +2.711 , (B): +0.28 , (C): –1.2 , (D): –2.87
The table above gives the standard oxidation potentials of four elements (A), (B), (C) and (D). The highest emf of a galvanic cell can be obtained from ..........

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

Which of the following represents a galvanic cell whose electrodes are chromium (Cr) and gold (Au), if the oxidation potential of chromium is (+0.74 V) and the reduction potential of gold is (+1.42 V)?

1. A Anode: Cr(s) → Cr³⁺(aq) + 3e⁻ , cathode: Au³⁺(aq) + 3e⁻ → Au(s) , E_cell = 2.16 V
2. B Anode: Au³⁺(aq) + 3e⁻ → Au(s) , cathode: Cr(s) → Cr³⁺(aq) + 3e⁻ , E_cell = 0.68 V
3. C Anode: Cr³⁺(aq) + 3e⁻ → Cr(s) , cathode: Au(s) → Au³⁺(aq) + 3e⁻ , E_cell = 2.16 V
4. D Anode: Au(s) → Au³⁺(aq) + 3e⁻ , cathode: Cr³⁺(aq) + 3e⁻ → Cr(s) , E_cell = 0.68 V

PbO₂(s) + SO₄²⁻(aq) + 4H⁺(aq) + 2Hg(l) + 2Cl⁻(aq) → Hg₂Cl₂(s) + PbSO₄(s) + 2H₂O(l)
Given that: (Pb²⁺ / Pb⁴⁺ = –1.69 V , Hg / Hg⁺ = –0.59 V)
The reaction above is ..........

1. A non-spontaneous , emf = –1.1 V
2. B spontaneous , emf = 1.1 V
3. C non-spontaneous , emf = –2.28 V
4. D spontaneous , emf = 2.28 V

From the opposite standard potentials:
X²⁺ + 2e⁻ → X E° = 1.5 V
Y → Y⁺ + e⁻ E° = 0.75 V
Z → Z²⁺ + 2e⁻ E° = 2.32 V
W³⁺ + 3e⁻ → W E° = 1.4 V
Which of the following choices is correct?

1. A The reaction (X²⁺ + 2Y → X + 2Y⁺) represents a galvanic cell and emf = (+0.75 V).
2. B The reaction (3Z + 2W³⁺ → 3Z²⁺ + 2W) represents an electrolytic cell and emf = (–3.44 V).
3. C The reaction (Z + X²⁺ → Z²⁺ + X) represents a galvanic cell and emf = (+3.82 V).
4. D The reaction (3Y + W³⁺ → 3Y⁺ + W) represents an electrolytic cell and emf = (–2.15 V).

The following reaction takes place in an electrochemical cell: Ni(s) + Fe²⁺(aq) → Ni²⁺(aq) + Fe(s)
Given that (oxidation potential of Ni = +0.23 V , oxidation potential of Fe = +0.4 V), which of the following is correct?

1. A The reaction is spontaneous , emf = –0.17 V
2. B The reaction is spontaneous , emf = +0.17 V
3. C The reaction is non-spontaneous , emf = –0.17 V
4. D The reaction is non-spontaneous , emf = +0.17 V

The following reactions take place in galvanic cells under standard conditions:
X + Y²⁺ → X²⁺ + Y emf = 0.351 V
Y + Z²⁺ → Y²⁺ + Z emf = 0.749 V
From the reactions above, the emf of the cell Z + X²⁺ → Z²⁺ + X is ..........

1. A –1.1 V
2. B 1.1 V
3. C 0.398 V
4. D –0.398 V

In a Daniell cell, when the zinc half-cell is replaced with a silver half-cell, which of the following is correct? Given the oxidation potentials of Ag and Zn: [E°(Ag) = –0.8 V , E°(Zn) = 0.76 V]

1. A The emf decreases and the direction of the current does not change.
2. B The emf increases and the direction of the current changes.
3. C The emf decreases and the direction of the current changes.
4. D The emf increases and the direction of the current does not change.

Given the opposite standard potentials:
X²⁺(aq) + 2e⁻ → X(s) E° = +0.34 V
Y²⁺(aq) + 2e⁻ → Y(s) E° = –0.76 V
Z²⁺(aq) + 2e⁻ → Z(s) E° = –2.375 V
If you have a primary galvanic cell made of two electrodes (X) and (Y), and half-cell (X) is replaced with half-cell (Z) under suitable conditions, which of the following choices is correct?

1. A The direction of the electric current changes and the emf decreases
2. B The direction of the electric current does not change and the emf decreases
3. C The direction of the electric current changes and the emf increases
4. D The direction of the electric current does not change and the emf increases