In research that required the careful measurement of gas densities, John Rayleigh, a physicist, found that the density of O₂(g) had the same value whether the gas was obtained from air or derived from one of its compounds. The situation with N₂(g) was different, however. The density of N₂(g) had the same value when the N₂(g) was derived from any of various compounds, but a different value if the N₂(g) was extracted from air. In 1894, Rayleigh enlisted the aid of William Ramsay, a chemist, to solve this apparent mystery; in the course of their work they discovered the noble gases.

(a) Why do you suppose that the N₂(g) extracted from liquid air did not have the same density as N₂(g) obtained from its compounds?

(b) Which gas do you suppose had the greater density: N₂(g) extracted from air or N₂(g) prepared from nitrogen compounds? Explain.

(c) The way in which Ramsay proved that nitrogen gas extracted from air was itself a mixture of gases involved allowing this nitrogen to react with magnesium metal to form magnesium nitride. Explain the significance of this experiment.

(d) Calculate the percent difference in the densities at 0.00 °C and 1.00 atm of Rayleigh’s N₂(g) extracted from air and N₂(g) derived from nitrogen compounds. [The volume percentages of the major components of air are 78.084% N₂, 20.946% O₂, 0.934% Ar, and 0.0379% CO₂.]