When we increase the concentration of H₂O in the first trial, this directly causes the equilibrium to shift left in accordance with Le Chatelier's principle.

In the second trial, (CH₃)₂CO (i.e., acetone) does not dissolve well in ethanol. It also does not noticeably react with any ions in the existing equilibrium. Therefore the addition of acetone does not affect postition of the equilibrium.

In the third trial, because NaCl does not dissolve well in alcohol, most of it remains solid. Therefore the concentration of Cl ^- increases only slightly. In response, the equilibrium shifts a little bit to the right, and there is a slight colour change (although it is difficult to notice).

In the fourth trial, AgNO₃ is highly soluble in alcohol and dissolves into Ag ⁺ and NO₃ ^- ions. These Ag ⁺ ions combine with Cl ^- to form AgCl (s). This reduces the concentration of Cl ^- ions and so the equilibrium shifts left in accordance with Le Chatelier's principle.