A teacher carried out a class demonstration on
diffusion similar to that using ammonia (M = 17)
and hydrochloric acid (M = 36.5) (Figure 1.21).
However, they replaced the ammonia with
methylamine (M = 31), which reacts in a similar
way to ammonia (note that M, is the relative
molecular mass of the substance).

Where would you predict the position of the
smoke ring to be in this experiment? Explain
your answer.
b Suggest other gases similar to hydrochloric
acid that could replace it in this demonstration
(use textbooks or the internet to find a
possible acid).
hydrog
air.