Which one of the following statements is not correct?

Option 2 is not correct. Colligative effects state that adding a non‑volatile solute lowers the chemical potential/activity of water, which leads to vapor‑pressure lowering and a consequent boiling‑point elevation; thus statements 1 and 3 are true. Osmotic phenomena assert that osmotic pressure is the pressure that must be applied to a solution to stop solvent influx through a semipermeable membrane, so statement 4 is also true. By contrast, addition of solute makes the solute potential (and hence overall water potential) more negative, so water potential decreases rather than increases — making statement 2 incorrect.