Worksheet: Rusting

In this worksheet, we will practice explaining the conditions necessary for rusting and writing balanced equations for the key reactions involved.

Q1:

When an iron nail rusts, it reacts with oxygen and water in the air. What happens to the total mass of the nail?

  • AIt stays the same
  • BIt decreases
  • CIt increases

Q2:

What is the name of the most abundant oxide produced by the rusting of iron?

  • AIron(IV) oxide
  • BIron(II) oxide
  • CIron(I) oxide
  • DIron(III) oxide
  • EIron(V) oxide

Q3:

Acid rain is produced when sulfur dioxide in the atmosphere reacts with water to form sulfuric acid. Increasing the acid concentration in rain causes an exposed iron surface to rust more quickly. Which of the following is not a mechanism by which dissolved acid accelerates rusting?

  • ADissolved ions increase the conductivity of water.
  • BThe products of rusting are made more soluble by a decrease in pH.
  • CHydrogen ions react with protective surface coatings.
  • DMetallic iron is made more soluble by a decrease in pH.
  • EHydrogen ions react with iron and oxygen to form iron ions.

Q4:

In which of the following environments would rusting of a steel plate occur most rapidly?

  • ARiver bed
  • BDesert
  • CRain forest
  • DOcean floor
  • EFrozen soil

Q5:

Two sealed iron tanks, 𝐴 and 𝐵 , contain identical volumes of water at room temperature. Tank 𝐴 contains water that was boiled before being placed in the tank, while the water in tank 𝐵 was not boiled. How and why does the rate of rusting differ between the two tanks?

  • AThe rate of rusting is higher in tank 𝐴 as boiling of water increases the amount of dissolved oxygen.
  • BThere is no difference in the rate of rusting.
  • CThe rate of rusting is lower in tank 𝐴 as boiling of water reduces the amount of dissolved salt.
  • DThe rate of rusting is lower in tank 𝐴 as boiling of water reduces the amount of dissolved oxygen.
  • EThe rate of rusting is higher in tank 𝐴 as boiling of water reduces the amount of dissolved salt.

Q6:

Rusting of iron is an example of an oxidation reaction. The rate of rusting of iron in water varies with increasing salt concentration.

Which particles are removed from a metal during an oxidation reaction?

  • AOxygen atoms
  • BProtons
  • CHydrogen atoms
  • DElectrons
  • ENeutrons

How and why does the rate of rusting of iron in water vary with increasing salt concentration?

  • AThe rate increases because dissolved ions aid the movement of charge.
  • BThe rate increases because dissolved ions aid the decay of metal nuclei.
  • CThe rate decreases because dissolved ions aid the ionization of water.
  • DThe rate decreases because dissolved ions react with dissolved oxygen.
  • EThe rate increases because dissolved ions react with the metal atoms.

Which term best describes the role of the salt solution in the rusting process?

  • AAcid
  • BOxidizing agent
  • CElectrolyte
  • DReducing agent
  • EBase

Q7:

Iron(III) hydroxide is a key product of rusting in humid conditions. This solid material forms from dissolved F e 3 + ions, which in turn are formed from solid iron. The reactions involve water, hydrogen ions ( H ) + , and oxygen molecules. Each step of the reaction can be represented using a net ionic equation, which is balanced based on the total charge on the two sides of the equation being equal.

Including state symbols, give a balanced net ionic equation for the formation of F e 3 + ions from metallic iron and dissolved hydrogen ions and oxygen molecules.

  • A 2 F e ( ) + 6 H ( ) + O ( ) 2 F e ( ) + 3 H O ( ) s a q a q a q l + 2 3 + 2
  • B 2 F e ( ) + 4 H ( ) + O ( ) 2 F e ( ) + 2 H O ( ) s a q a q a q l + 2 3 + 2
  • C 4 F e ( ) + 1 2 H ( ) + 3 O ( ) 4 F e ( ) + 3 H O ( ) s a q a q a q l + 2 3 + 2
  • D 4 F e ( ) + 1 2 H ( ) + 3 O ( ) 4 F e ( ) + 6 H O ( ) s a q a q a q l + 2 3 + 2
  • E 4 F e ( ) + 6 H ( ) + 3 O ( ) 4 F e ( ) + 3 H O ( ) s a q a q a q l + 2 3 + 2

Including state symbols, give a balanced net ionic equation for the formation of iron(III) hydroxide from F e 3 + ions and water molecules.

  • A F e ( ) + 3 H O ( ) F e ( O H ) ( ) + 3 H ( ) 3 + 2 3 + a q l s a q
  • B F e ( ) + 6 H O ( ) F e ( O H ) ( ) + 6 H ( ) 3 + 2 3 2 a q l s g
  • C 2 F e ( ) + 6 H O ( ) 2 F e ( O H ) ( ) + 3 H ( ) 3 + 2 3 2 a q l s g
  • D F e ( ) + 3 H O ( ) F e ( O H ) ( ) + 6 H ( ) 3 + 2 3 + a q l s a q
  • E 2 F e ( ) + 3 H O ( ) 2 F e ( O H ) ( ) + 3 H ( ) 3 + 2 3 + a q l s g

How many hydrogen ions are consumed in total when an atom of iron is converted to iron(III) hydroxide?

Iron(III) hydroxide can be dehydrated to produce a material containing no hydrogen atoms. How many water molecules are removed for every atom of iron in the material?

Q8:

Vehicles on major roads are found to rust much more rapidly in cold wet countries when the temperature is below freezing. Which factor is most directly responsible for this effect?

  • AHumidity
  • BTemperature
  • COxygen
  • DSalt
  • EpH

Q9:

A steel chain submerged in water is susceptible to rusting. What effect is observed if sodium chloride is added to the water to produce a saturated solution?

  • ANo rusting takes place.
  • BThe steel chain rusts less quickly.
  • CThe steel chain reacts to form a chloride salt.
  • DThe steel chain rusts more quickly.
  • EThe steel chain reacts to produce a sodium-iron alloy.

Q10:

Which of the following is not a role played by water when iron rusts in neutral water?

  • AWater is incorporated into the final solid material.
  • BWater dissolves iron ions.
  • CWater reacts with oxygen to generate hydroxide ions.
  • DWater reacts with iron to form hydrogen molecules.
  • EWater dissolves oxygen gas.

Q11:

The density of iron is 7.87 g/cm3. When iron is oxidized during rusting, the density decreases to 5.24 g/cm3. By contrast, the density of aluminum is 2.70 g/cm3 and this value increases to 3.99 g/cm3 when the metal is completely oxidized.

What is the percentage change in volume when iron is converted completely to rust? Assume that no water is present at the end of the reaction.

What is the percentage change in volume when aluminum is completely oxidized?

Changes in volume during oxidation affect the amount of cracking caused by oxidation. How do the volume changes of iron and aluminum differ, and what effect does this difference have on the amount of cracking?

  • AAluminum expands less than iron when oxidized, so more cracking occurs.
  • BUnlike iron, aluminum contracts when oxidized, so more cracking occurs.
  • CAluminum expands less than iron when oxidized, so less cracking occurs.
  • DUnlike iron, aluminum contracts when oxidized, so less cracking occurs.
  • EAluminum expands more than iron when oxidized, so less cracking occurs.

Q12:

Why does rusting affect iron more than aluminum?

  • AAluminum binds to water less strongly.
  • BAluminum is less reactive than iron.
  • CAluminum oxides are less soluble than iron oxides.
  • DAluminum is protected by a surface oxide layer.
  • EAluminum oxides are less stable than iron oxides.

Q13:

Give a balanced chemical formula for the formation of the major iron oxide compound in rust.

  • A 3 F e + O F e O 2 3 2
  • B 2 F e + O 2 F e O 2
  • C F e + O F e O 2 2
  • D 4 F e + 3 O 2 F e O 2 2 3
  • E 3 F e + 2 O F e O 2 3 4

Q14:

Two moles of iron react with one mole of oxygen to produce a colored compound of uniform composition. All of the iron reacts and there are no other products.

What is the formula of the compound produced?

  • A F e O 3 2
  • B F e O 2 3
  • C F e O 3 4
  • D F e O
  • E F e O 2

What color is the compound produced?

  • ABlack
  • BYellow
  • CGreen
  • DRed
  • EWhite

The compound reacts with further oxygen to form a more stable material. What color is the new material?

  • AWhite
  • BBlack
  • CRed
  • DGreen
  • EYellow

Q15:

A thin 25.0 kg sheet of iron rusts in wet air containing excess oxygen. The iron is uniformly converted to a single material consisting of iron, oxygen, and water. The material contains 1 molecule of water for every 2 iron atoms reacted.

What mass of oxygen reacts with the iron during this process?

To 3 significant figures, what is the iron content of the product as a percentage of the total mass?

Q16:

When rust is formed on the surface of iron, it does not prevent further oxidation of the remaining metal. What is the main reason that rust does not behave as a protective coating?

  • ARust accelerates oxidation by binding to water in the air.
  • BRust reacts with metallic iron, catalyzing its own formation.
  • CRust accelerates oxidation by lowering the pH at the iron surface.
  • DRust forms flakes that adhere weakly to the iron surface.
  • ERust forms a thin layer on the iron surface and is easily dissolved.

Q17:

A shiny iron nail will rust over time. As it rusts, what happens to the total mass?

  • AIt stays the same
  • BIt decreases
  • CIt increases

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