An iron printing plate is kept in a closed display case. Air entering the case passes through anhydrous calcium chloride. After prolonged use, the calcium chloride can no longer remove water vapour.
Why could rust now form on the plate?
Both water and oxygen can now reach the iron, and rusting requires both substances.
Oxygen was already reaching the iron, and oxygen alone is sufficient for rusting.
Water and oxygen can now reach the iron, but either substance alone causes rusting.
Water can now reach the iron, and water alone is sufficient for rusting.
118 exam-style questions on AQA GCSE Chemistry 10.3 Using materials, covering 10.3.1 Corrosion and its prevention, 10.3.2 Alloys as useful materials, and 10.3.3 Ceramics, polymers and composites. Each one has a worked solution and a mark scheme showing where the marks go.