Marine propeller hubs are often manufactured from a high-strength copper alloy to withstand extreme mechanical stress and resist seawater corrosion.
A specific propeller hub has a total mass of 4.50 kg4.50\text{ kg}4.50 kg. The table below details the mass of each element present in this hub:
| Element | Mass in kg\text{kg}kg |
|---|---|
| Copper | 3.69 |
| Aluminium | 0.45 |
| Nickel | 0.27 |
| Iron | 0.09 |
Calculate the percentage by mass of copper in this propeller hub.
Explain why this copper alloy is used instead of pure copper to manufacture the propeller hub.