Osmotic pressure is the minimum amount of pressure a solution must exert in order to prevent from crossing a barrier by osmosis. Solute molecules have difficulty crossing semipermeable membranes, so the more solutes that are in a solution, the higher the osmotic pressure will be. Between 30% sucrose and 60% sucrose, 60% sucrose will have a greater osmotic pressure than 30% because it has a higher percentage of solutes. However, since sucrose has a higher potential to cross semipermeable membranes and is more absorbable than magnesium sulfate, magnesium sulfate would have a higher osmotic pressure than 60% sucrose even though 60% sucrose has higher molecules.