The effect of solute concentration on the colligative properties of water is independent of the chemical properties of the solute; it depends only on the number of solute particles in a given amount of water. -Example: NaCl will have twice the effect on osmotic pressure as will glucose.-Solutes alter the colligative properties of aqueous solutions by lowering the effective concentration of water .-When a significant fraction of the molecules at the surface of an aqueous solution are not water but solute, the tendency of water molecules to escape into the vapor phase ( the vapor pressure ) is lowered. This means that the solution will take longer to boil, and will have a higher boiling point .-Similarly, the tendency of water molecules to move from the aqueous phase to the surface of a forming ice crystal is reduced when some of the molecules that collide with the crystal are solute, not water. In this case, the solution will freeze more slowly than pure water, and at a lower temperature
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