My textbook states that the higher concentration of solutes, the greater the osmotic pressure will be and the greater the pull of water in will be. However, osmotic pressure is defined "as the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis." Therefore wouldn't a high osmotic pressure PREVENT water from passing, not pull water in? Can someone please clarify this for me so it makes sense? Thank you!
I think you've got the solutions the wrong way round and that you should be applying the pressure on the non-pure solution, not the pure solution. Pure water is drawn in through the membrane so you have to put pressure on the non-pure solution to keep it out. Which textbook are you using? See the following quote from Voet et al. 5th ed. p. 30 and figure from Lehninger. Principles of Biochemistry p. 57.
The osmotic pressure of a solution is the pressure that must be applied to the solution to equalize the flow of water across the membrane in both directions (the added pressure forces more water from the solution through the membrane); it is proportional to the concentration of the solute.