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Unformatted text preview: Chapter 13: Properties of Solutions This chapter is actually very difficult even though it only involves three sections. These three sections cover many different laws and equations. The first section is about the three different factors which affect the solubility of a solution. Next, new ways of expressing the concentration of a solution are explored. Finally, this chapter is finished off by discussing properties of solutions which depends upon the quantity of the solutes and solvents. And just a warning: you must integrate all of these topics into your head together. I t is very likely that on exams many of the equations and laws you see here will be combined into one, so good dimensional analysis skills are key. Also, make sure you learn and understand all of the topics; otherwise, the concept questions will have fun with you as this is new, hard stuff. Section 13.3: Factors Affecting Solubility This section talks about the topic of solubility. Solubility is simply how easily one substance (the solute ) dissolves in another substance (the solvent ). The solvent is the substance which there is more of. The main focus of this section is on the three factors which affect solubility. These factors are: 1. Types of Molecules 2. Pressure 3. Temperature 1. Types of Molecules This has to deal primarily with the intermolecular forces which we talked about in Chapter 11. If a solute and a solvent are strongly attracted to each other, then they are likely to be more soluble. This is especially t rue of water since it can form hydrogen bonds. Also, if two substances are both non-polar, they will mix better than a polar and a non-polar substance since they are more equally attracted to each other. Basically, the more alike the intermolecular forces between two substances, the more soluble they will be. So, when talking about water, alkanes will not dissolve since they are non-polar while water is polar and capable of forming hydrogen bonds. If two liquids do not mix together, they are said to be immiscible . On the other hand, alcohols , which have a polar OH group on the end (which is capable of forming hydrogen bonds with water because of the non-bonding electron domains on the Oxygen atom), dissolve easily in water. Two liquids which mix together easily are said to be miscible . This is especially t rue of small alcohols such as ethanol. As alcohol molecules get larger, however, the OH group becomes a much smaller part of the molecule and they behave more like alkanes. Note that solids such as diamond or quartz are not very soluble because of the strong bonding forces within the solid. 2. Pressure Pressure only has an effect upon soluble gases. Solubility happens to be directly proportional to the pressure of the gas. So, if there was a gas in equilibrium above a solution, and the volume was halved, the pressure would double, causing gas particles to enter and leave the solution faster, increasing solubility. This is expressed mathematically in yet another law known as...
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This note was uploaded on 03/10/2009 for the course CHEM 110 taught by Professor Hofmann,brucerob during the Fall '08 term at Pennsylvania State University, University Park.
- Fall '08