A thin glass tube 1 m long is filled with Ar gas at 101.3 kPa,
and the ends are stoppered with cotton plugs as shown
below. HCl gas is introduced at one end of the tube, and simultaneously NH3 gas is introduced at the other end. When
the two gases diffuse through the cotton plugs down the
tube and meet, a white ring appears due to the formation of
NH4Cl1s2. At which location—a, b, or c—do you expect the
ring to form?