Oxygen and water are both required for iron to rust.
Apart from oxygen, state the other substance essential for iron to rust.
Initial corrosion of iron often produces a compound with the chemical formula Fe(OH)2\text{Fe(OH)}_2Fe(OH)2. State the chemical name of this compound, including its oxidation state.
Three students, Amara, Ben, and Chloe, carried out an investigation on the corrosion of three different steel plates. They recorded the mass of each plate before the experiment. After several days of exposure to moist air, they measured the mass of each plate again.
Their results are shown in the table below:
| Student | Mass of plate before (g) | Mass of plate after (g) |
|---|---|---|
| Amara | 8.0 | 8.6 |
| Ben | 3.0 | 3.3 |
| Chloe | 6.0 | 5.8 |
Suggest one difficulty in obtaining an accurate mass of the corroded plate at the end of the experiment.
Amara concluded that her plate rusted the most. Suggest a reason to justify her conclusion.
Ben argued that his plate rusted the most. Explain how he could justify this argument using the data in the table.
Chloe's results show a decrease in mass. Explain why a decrease in mass indicates that an error must have occurred during her experiment.
Many steel objects are protected from corrosion using a physical barrier to exclude oxygen and water.
Choose the most appropriate barrier from the box below for each of the two steel objects.
plastic coating∣grease∣paint∣electroplating \text{plastic coating} \quad | \quad \text{grease} \quad | \quad \text{paint} \quad | \quad \text{electroplating} plastic coating∣grease∣paint∣electroplatingAn outdoor steel girder: _______
Moving engine gears: _______
Steel (which consists mainly of iron) can also be protected by attaching sacrificial blocks of magnesium. State the name of this type of protection and explain how it works to prevent the steel from corroding.
34 exam-style questions on Edexcel IGCSE Chemistry Reactivity series. Each one has a worked solution and a mark scheme showing where the marks go.