# When a bottle of conc. ammonia is opened next to an open bottle of conc. hydrochloric acid, a fine white residue forms in mid-air BETWEEN the open bottles. How do we rationalize this observation?

$N {H}_{3} \left(g\right) + H C l \left(g\right) \rightarrow N {H}_{4} C l \left(s\right) \downarrow$