The Effect of Solute on the Vapour Pressure of a Solution A.Equilibrium occurs between a pure liquid and its vapour when the numbers of molecules vaporising and condensing in a given time are equal. Rate of vaporisation Rate of condensation B.With a non-volatile solute present,fewer solvent molecules vaporise in a given time,so fewer molecules need to condense to balance them.Thus equilibrium is reached at a lower vapour pressure. PDF文件使用"pdfFactory Pro”试用版本创建www.fineprint.com.cn 7 The Effect of Solute on the Vapour Pressure of a Solution n A. Equilibrium occurs between a pure liquid and its vapour when the numbers of molecules vaporising and condens condensing in a given time are equal. n Rate of vaporisation = Rate of condensation n B. With a non-volatile solute present, fewer solvent molecules vaporise in a given time, so fewer molecules need to condense condense to balance them. Thus equilibrium is reached at a lower vapour pressure. PDF 文件使用 "pdfFactory Pro" 试用版本创建 www.fineprint.com.cn