Chem 112 Exam AID Course Pack

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Unformatted text preview: hange. For example, freezing point depression, boiling point elevation; similarly, a solution of NaCl in water will conduct electricity but neither component can do so on its own. Ethan Newton & Barry Zhang for SOS Winter 2012 21 − The major component of a solution is the solvent, and all other components are solutes. The more solute there is, the more concentrated and less dilute the solution becomes. − Eventually, there will be too much solute for the solution to hold, and it will precipitate out (or bubble out, in the case of a gas). This is because the solution is formed by multiple solvent molecules surrounding and interacting with each solute molecule, and eventually there will be too much solute – all the solvent will already be taken up. − Solutions are usually described in terms of molarity (mol/L, or M), the number of moles of solute per litre of solution, or molality (mol/kg, or m), the number of moles of solute per kilogram of solvent. − Molarity is affected by temperature, since volume changes with temperature, while molality is not. − Solutions are also described in terms of mass fraction (mass of solute over total mass) and mole fraction (moles of solute over total mass). Either of these can also be expressed as a percentage. − Gas phase solutions form easily; solid phase solutions are more difficult (and usually require melting). Liquids may or may not form solutions, based on their molecular properties. If they can form a solution, the liquids are called miscible (if not, immiscible). − Miscible liquids can be separated by distillation, in which the temperature is raised above the boiling point of one liquid but not above the boiling point of the other. The lower- boiling liquid will enter gaseous phase (and is drawn off) while the higher- boiling liquid stays where it is. − (In practice, though, it’s not perfect, since some molecules from the higher- boiling liquid will have enough energy to enter the gaseous phase as well). − In general, a liquid solution of A and B will not form if the intermolecular forces between the molecules of A are stronger than those that would be formed between A and B. The molecules of A will not readily enter the weaker interactions with the other molecules. − Thus, in general, the interactions of A with A...
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This note was uploaded on 10/02/2012 for the course CHEM 112 taught by Professor Carran during the Winter '08 term at Queens University.

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