Using materials (chemistry only)：練習題

Which of the following describes the conditions required for iron to rust?

Which of the following statements best explains why alloys are harder than pure metals?

The Haber process uses a temperature of approximately \(450^{\circ}C\) and a pressure of \(200\) atmospheres. Why is \(450^{\circ}C\) used despite the forward reaction being exothermic?

What is the primary difference between thermosoftening and thermosetting polymers when heated?

A sample of 24 carat gold is 100% pure gold. If a piece of jewellery is described as 18 carat gold, what is the percentage of gold by mass in the alloy?

Corrosion and its Prevention

Iron and steel are commonly used materials that are susceptible to rusting. Rusting is an example of corrosion that requires both air and water.

a) Describe an experiment that could be performed to show that both air and water are necessary for iron to rust. [3]

b) Explain the process of sacrificial protection in terms of relative reactivity and how it prevents the corrosion of iron. [2]

c) Aluminium is more reactive than iron, yet it is much more resistant to corrosion in everyday conditions. Explain why aluminium does not corrode as easily as iron when exposed to the atmosphere. [2]