Question map
Which one of the following is the correct order in which the gases H2, Ne, O2, and N2 are evolved on fractional distillation of liquid air?
Explanation
Fractional distillation of liquid air separates components based on their boiling points [t1][t3]. During this process, the liquid air is gradually warmed, and gases with the lowest boiling points evaporate (evolve) first [t1][t2]. The boiling points of the specified gases are: Hydrogen (H2) at approximately -252.9°C (20.3 K), Neon (Ne) at -246.1°C (27.1 K), Nitrogen (N2) at -195.8°C (77.4 K), and Oxygen (O2) at -183.0°C (90.2 K) [t1][t6]. Since H2 has the lowest boiling point, it evolves first, followed by Ne, then N2, and finally O2, which has the highest boiling point among the group and remains liquid the longest [t1]. This sequence (H2 < Ne < N2 < O2) follows the order of increasing boiling points, making option 2 the correct sequence for evolution during distillation.