Question 5 – Group 0 - Edexcel GCSE Chemistry Questions

Figure 1 shows a robotic welding torch designed to join aerospace titanium components. Titanium is highly reactive with oxygen and nitrogen at welding temperatures. To prevent contamination, a shielding gas is fed downwards from the torch nozzle to blanket the horizontal weld pool and displace air.

Robotic welding setup with shielding gas directed downwards onto a titanium plate.

Table 1 shows the reactivity and density, at room temperature and pressure, of helium, nitrogen, and argon.

Table 1

Gas	Reactivity at high temperatures	Density at room temperature and pressure ( $dm−3\text{g dm}^{-3}$ )
Helium	Unreactive	0.16
Nitrogen	Reacts with titanium	1.15
Argon	Unreactive	1.65

The density of air under these same conditions is 1.20 g dm^-3.

Explain why nitrogen and why helium are not suitable for use as the shielding gas in this welding setup.

Robotic welding setup with shielding gas directed downwards onto a titanium plate.

Table 1 shows the reactivity and density, at room temperature and pressure, of helium, nitrogen, and argon.

Table 1

Gas	Reactivity at high temperatures	Density at room temperature and pressure ( $dm−3\text{g dm}^{-3}$ )
Helium	Unreactive	0.16
Nitrogen	Reacts with titanium	1.15
Argon	Unreactive	1.65

The density of air under these same conditions is 1.20 g dm^-3.

Explain why nitrogen and why helium are not suitable for use as the shielding gas in this welding setup.

Table 1

Group 0 Questions

Table 1

Group 0 Questions