When metals are welded, the hot metal is protected by a stream of argon gas. The argon surrounds the weld and keeps air away from it.
The table shows the densities of some gases at room temperature and pressure.
| Gas | Density in g dm−3\mathrm{g\,dm^{-3}}gdm−3 |
|---|---|
| air | 1.20 |
| argon | 1.67 |
| helium | 0.167 |
Explain why argon is used to protect the hot metal during welding.
Helium is also a noble gas. Suggest why argon is better than helium for protecting a weld on a flat surface. Use the data in the table.
A welder uses 9000 dm3\mathrm{dm^{3}}dm3 of argon, measured at room temperature and pressure.
Use the equation: mass=density×volume\text{mass} = \text{density} \times \text{volume}mass=density×volume
Calculate the mass of argon used. Give your answer in kg.
Air contains 0.93% argon by volume. Calculate the volume of argon in 2000 dm3\mathrm{dm^{3}}dm3 of air.
38 exam-style questions on Edexcel GCSE Chemistry 7.3 Group 0, covering 7.3.1 The noble gases. Each one has a worked solution and a mark scheme showing where the marks go.