Corrosion of Metals questions

The metal that corrodes ..........

1. A gains electrons.
2. B undergoes a reduction process.
3. C has its oxidation number decreased.
4. D acts as the reducing agent.

The following statements are true concerning the corrosion of metals, except ..........

1. A The oxidation of most metals is a spontaneous process.
2. B Some metals are covered with a thin layer of their oxides that protects the inner atoms from corrosion.
3. C The rate of rusting of iron in H₂SO₄ solution is greater than in CH₃COOH solution.
4. D Iron found in meteorites in outer space is easily oxidized.

Rusting takes place faster when the water causing the rust contains ..........

1. A ammonia gas.
2. B sodium chloride salt.
3. C calcium sulphate.
4. D aluminium hydroxide.

Iron rusts when it reacts with (1), and iron can be protected from rusting by bringing it into contact with metal (2).
Which of the following is correct?

1. A (1): oxygen only , (2): copper.
2. B (1): oxygen only , (2): magnesium.
3. C (1): oxygen + water vapour , (2): copper.
4. D (1): oxygen + water vapour , (2): magnesium.

Iron oxide ores are converted into iron by process (1), and iron rusts by process (2).
Which of the following is correct?

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

All of the following describe exposing an iron rod containing a percentage of carbon to moist air, except ..........

1. A The iron rod acts as both the anode and the external circuit.
2. B Reduction takes place at the carbon.
3. C Carbon acts as the cathode.
4. D The percentage of iron increases.

The carbon in a steel alloy does not corrode when the alloy rusts, because it acts as the ..........

1. A electrolyte.
2. B anode.
3. C cathode.
4. D external circuit.

The opposite figure shows the mechanism of the corrosion of iron.
Which of the following is correct?

1. A (1): e⁻ , (2): Fe²⁺(aq) , (3): O₂
2. B (1): Fe²⁺(aq) , (2): O₂ , (3): e⁻
3. C (1): Fe³⁺(aq) , (2): Fe(OH)₃(s) , (3): O₂
4. D (1): Fe²⁺(aq) , (2): e⁻ , (3): Fe(OH)₃(s)

Which of the following represents the correct order of the chemical processes that take place on the surface of a piece of iron exposed to moist air?

1. A Oxidation – reduction – precipitation – reduction.
2. B Oxidation – reduction – precipitation – oxidation.
3. C Oxidation – oxidation – reduction – precipitation.
4. D Reduction – oxidation – precipitation – oxidation.

All of the following are used to distinguish between the rust compound of iron and the hydroxide of the non-transition element used in making the alloy of soft-drink cans, except ..........

1. A melting point.
2. B NaOH(aq)
3. C colour.
4. D H₂O(l)

Which pair of the following reactions is represented by the same chemical equation?

1. A The anode reaction in the fuel cell and the anode reaction in the iron rusting cell.
2. B The cathode reaction in the mercury cell and the cathode reaction in the Daniell cell.
3. C The cathode reaction in the fuel cell and the cathode reaction in the iron rusting cell.
4. D The anode reaction in the lead-acid accumulator during discharge and the anode reaction in a galvanic cell whose electrodes are Zn , Pb

The opposite figure shows an experiment to show the effect of coating with an inorganic substance such as red lead on the rusting of iron.
What happens, after a period of time, to the water level in each of tubes (P) and (Q), respectively?

1. A Falls , rises.
2. B No change , rises.
3. C Rises , no change.
4. D No change , falls.

From the oxidation potentials shown in the following table:
Metal (1): –0.8 V , metal (2): +0.74 V , metal (3): –0.34 V , metal (4): +0.45 V , Pb: +0.13 V
Which of these metals can be used as a cathodic coating for lead?

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

The following figures represent four different experiments:
Which of the following represents the order of the rate of rusting of the nail in the four experiments?

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

Bringing iron into contact with a piece of zinc protects it from rusting, as a result of ..........

1. A the transfer of electrons from iron to zinc.
2. B zinc being reduced faster than iron.
3. C the transfer of electrons from zinc to iron.
4. D the reduction of oxygen gas at the zinc.

The following statements show a student's understanding of the role of zinc in protecting the surface of iron from rusting:
(1): Zinc acts as an anode and iron as a cathode.
(2): The zinc layer protects iron from moisture and air.
(3): The zinc layer acts as a cathodic coating for iron.
Which of the following represents the role of zinc?

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

From the following statements:
(1): Iron can be protected from rusting by coating it with tin.
(2): Rusting takes place when water and air are available.
(3): Rust is an alloy of iron and oxygen.
(4): Anodic protection is done by connecting iron to another metal less active than it.
Which of the previous statements are correct?

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

All of the following represent the use of a sacrificial electrode to protect a steel tank buried underground, except ..........

1. A connecting the tank to a piece of copper.
2. B connecting the tank to a piece of magnesium.
3. C connecting the tank to a piece of calcium.
4. D connecting the tank to a piece of zinc.

If the oxidation potential of iron Fe equals +0.401 V
then the potential of the metal that can be used as an anodic coating for iron is ..........

1. A [E°oxid = 1.29 V]
2. B [E°oxid = –1.5 V]
3. C [E°oxid = 0.13 V]
4. D [E°oxid = – 0.34 V]

From the opposite standard potentials:
A / A²⁺ : E° = 0.76 V
B⁺ / B : E° = 0.8 V
C / C²⁺ : E° = 0.56 V
Which of the following metals acts as a sacrificial electrode?

1. A Metal (B) relative to metal (A).
2. B Metal (B) relative to metal (C).
3. C Metal (A) relative to metal (C).
4. D Metal (C) relative to metal (A).

A piece of iron can be protected from rusting by ..........

1. A making it a cathode.
2. B placing it in a neutral salt solution.
3. C bringing it into contact with a piece of lead.
4. D bringing it into contact with a piece of gold.

Which of the following increases the rate of rusting of an iron nail immersed in water?

1. A Adding calcium carbonate salt to the water.
2. B Wrapping the nail with a thin strip of zinc.
3. C Adding potassium nitrate salt to the water.
4. D Connecting the nail to the negative terminal of an electric source.

Which of the following represents the case in which the iron nail corrodes at a faster rate?

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

The following figures show four experiments carried out using four identical iron rods placed in water:
The two experiments in which the iron rod rusts first are ..........

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

From the opposite figure:
The sheet that rusts faster when it is scratched is ..........

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

When iron rusts, the ion produced from the oxidation process combines with the ion produced from the reduction process, forming compound (X):
(1) Write the equation for the formation of compound (X), stating its colour after being exposed to air.
(2) What change takes place in the colour of compound (X) over time? Explain.

The opposite figure shows an iron pipe being protected from rusting by connecting it to a rod of metal (X):
(1) Does metal (X) replace iron in solutions of its salts? Explain.
(2) What change takes place in the mass of each of the rod and the iron pipe over time? Explain.

From the opposite figure:
(1) Which of the two electrodes (X) or (Y) can be used in galvanizing metals? Explain.
(2) Write the equation of the actual reaction taking place on the surface of each of:
(a) electrode (X).
(b) electrode (Y).

The opposite table represents the standard reduction potentials of metals (A , B , C):
(A): –0.44 V , (B): +0.34 V , (C): +0.8 V
When each of metals (A) and (B) is separately coated with a layer of metal (C),
which of the following represents the correct type of protection?

1. A Anodic protection for (A) and cathodic for (B).
2. B Cathodic protection for (A) and cathodic for (B).
3. C Anodic protection for (A) and anodic for (B).
4. D Cathodic protection for (A) and anodic for (B).

The opposite table shows four galvanic cells made of hypothetical metals with an iron electrode under standard conditions:
A – Fe: cell potential +1.4 V , direction of electron flow A → Fe
B – Fe: cell potential +1.05 V , direction of electron flow Fe → B
C – Fe: cell potential +0.5 V , direction of electron flow C → Fe
D – Fe: cell potential +1.7 V , direction of electron flow Fe → D
Which of the following metals is preferably used as a sacrificial electrode for iron to protect it from rusting?

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

The following table represents the electrode potentials of four metals (X , Y , Z , W):
X²⁺ / X = 0.34 V , Y / Y²⁺ = –1.2 V , Z²⁺ / Z = –2.375 V , W / W²⁺ = –1.42 V
[Zn → Zn²⁺ + 2e⁻ , E° = 0.76 V]
Which of these metals corrodes fastest when it is in contact with zinc metal?

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

Which of the following examples represents cathodic protection of metals from corrosion?

1. A Painting iron with an inorganic substance such as red lead.
2. B Galvanizing iron by dipping it in zinc.
3. C Coating iron with a metal that has a lower reduction potential than iron.
4. D Coating iron with a metal that has a lower oxidation potential than iron.

The opposite table shows the oxidation potentials of some hypothetical elements:
W: +1.67 V , Z: –1.420 V , Y: –0.401 V , X: +0.126 V
Which of the following represents the correct type of protection?

1. A (X) is anodic protection for (W).
2. B (Z) is anodic protection for (Y).
3. C (W) is cathodic protection for (Y).
4. D (Y) is cathodic protection for (X).

The opposite figure shows one of the methods of protecting iron pipes buried in the ground from rusting.
Which of the following represents metal (X)?

1. A (X): does not replace hydrogen ions in acids, so the direction of electrons is number (2).
2. B (X): reduces iron ions in their solution, so the direction of electrons is (1).
3. C (X): its ions are reduced by iron atoms, so the direction of electrons is (1).
4. D (X): its oxidation potential is higher than iron, so the direction of electrons is (2).

The opposite table shows the reduction potentials of some elements.
(A): –0.45 V , (B): –1.7 V , (C): –2.87 V , (D): –2.52 V
Which of the following elements can be used as a sacrificial electrode for element (B)?

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

The figure in front of you shows a water tank connected to a pipe and a tap made of three metals (X , Y , Z),
whose reduction potentials are as follows: (X = –0.40 V , Y = +0.3 V , Z = –2.71 V)
The pipe acts as a sacrificial electrode for both the tank and the tap, and the material the tap is made of represents cathodic protection for the tank under normal conditions.
Which of the following choices represents the metals that each of them is made of?

1. A Tank: (Y) , tap: (X) , pipe: (Z)
2. B Tank: (X) , tap: (Y) , pipe: (Z)
3. C Tank: (X) , tap: (Z) , pipe: (Y)
4. D Tank: (Z) , tap: (Y) , pipe: (X)

The following table shows the potentials of some elements:
A → A²⁺ : E° = –1.2 V
B → B²⁺ : E° = –2.87 V
C²⁺ → C : E° = –1.2 V
D²⁺ → D : E° = –0.12 V
Which of the following choices is correct?

1. A Element (A) represents cathodic protection for element (B).
2. B Element (B) represents a sacrificial electrode for element (D).
3. C Element (C) represents anodic protection for element (A).
4. D Element (D) represents a sacrificial electrode for element (C).

The electrolyte that leads to faster corrosion of metals is ..........

1. A H₂SO₄ (0.5 M)
2. B HCl (0.5 M)
3. C HNO₂ (1 M)
4. D H₂SO₃ (1 M)

The following table shows the electrode potentials of several metals:
Reduction potential: Fe = –0.409 V , (X) = –2.375 V , (Y) = –1.67 V , (Z) = –0.23 V
You have four pieces of iron: part of the first was coated with (X), part of the second was coated with (Y), part of the third was coated with (Z), and the fourth was left uncoated. The piece that rusts fastest is the ..........

1. A first.
2. B third.
3. C fourth.
4. D second.

From the opposite equation: Ba(s) + Cr²⁺(aq) → Ba²⁺(aq) + Cr(s)
Which of the following choices is correct for protecting each of the two metals from corrosion?

1. A Coating barium with chromium, a cathodic coating.
2. B Coating barium with chromium, an anodic coating.
3. C Coating chromium with barium, a cathodic coating.
4. D Coating chromium with barium, an anodic coating.

If you know that the oxidation potential of element (X) = + 0.409 V, then the element that can be used as cathodic protection for element (X) is ..........

1. A an element whose standard reduction potential = – 0.76 V
2. B an element whose standard oxidation potential = + 1.03 V
3. C an element whose standard reduction potential = – 0.136 V
4. D an element whose standard oxidation potential = + 0.74 V

A piece of element (X) was coated with a layer of element (Y). If you know that the standard reduction potential of element (X) = –0.409 V and the standard reduction potential of element (Y) = –2.375 V,
which of the following represents this process correctly?

1. A Anodic protection, and reduction of the ions of element (X) takes place.
2. B Anodic protection, and reduction of the oxygen of moist air takes place.
3. C Cathodic protection, and reduction of the oxygen of moist air takes place.
4. D Cathodic protection, and reduction of the ions of element (X) takes place.

The following table shows the standard reduction potentials of elements (Z) , (Y) , (X) , (W):
(Z): –1.66 V , (Y): –0.74 V , (X): –0.25 V , (W): –2.37 V
Which of the following represents anodic protection?

1. A Element (Y) is coated with element (Z).
2. B Element (Y) is coated with element (X).
3. C Element (W) is coated with element (Z).
4. D Element (W) is coated with element (X).

The following table represents four reduction potentials of four elements (A) , (B) , (C) , (D), respectively:
(A): –1.66 V , (B): –2.37 V , (C): +0.799 V , (D): –1.26 V
Which of the previous elements can be used as a sacrificial element relative to another element?

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

The standard reduction potentials of elements (X) , (Y) , (Z) are as in the table:
(X): –0.28 V , (Y): +1.2 V , (Z): –1.029 V
Which of the following coatings makes the coated metal corrode fastest when scratched?

1. A Coating element (X) with element (Z).
2. B Coating element (Z) with element (Y).
3. C Coating element (Y) with element (X).
4. D Coating element (X) with element (Y).

The following table represents the oxidation potentials of elements (X) , (Y) , (Z):
(X): 0.3 V , (Y): 2.3 V , (Z): 0.7 V
When each of elements (X) and (Y) is separately coated with element (Z), which of the following represents the correct protection?

1. A Cathodic protection for (X) and anodic protection for (Y).
2. B Anodic protection for (X) and cathodic protection for (Y).
3. C Anodic protection for (X) and anodic protection for (Y).
4. D Cathodic protection for (X) and cathodic protection for (Y).

To protect element (A) by element (B) from corrosion, there takes place ..........

1. A withdrawal of electrons from (A) to (B), and it represents anodic protection.
2. B withdrawal of electrons from (B) to (A), and it represents anodic protection.
3. C transfer of electrons to (A), and it represents cathodic protection.
4. D transfer of electrons between (A) , (B), and (A) represents a sacrificial electrode.