Solubility Chapter Notes

Solutions A solution is a homogeneous mixture consisting of a single phase Sugar dissolved in water is a solution in the liquid phase When the sugar is dissolved, I could take a sample from any one part of the mixture and it would look the same as a sample taken from any other part of the mixture Solutions can be gases (air is a gas solution of oxygen and nitrogen) or solids (brass is a solid solution of copper and zinc; stainless steel is a solid solution of iron, chromium, nickel, and carbon)

Solvent vs. Solute When describing solutions, the solvent is the component that is present in the largest amount The solute is the component present in the smaller amount There can be multiple solutes in a solution Example: the air we breathe out is 75% nitrogen, 14% oxygen, 5% carbon dioxide, and 6% water vapor—nitrogen would be the solvent and oxygen, carbon dioxide, and water vapor are all solutes If we mix 1 teaspoon of sugar in 1 liter of water, which is the solvent and which is the solute? Water would be the solvent and sugar would be the solute

Concentration of Solution Process of a solute mixing in a solvent is called dissolving A solute must dissolve within a solvent in order to form a solution—it has to be a homogeneous mixture There can be a limit as to how much of a given solute can dissolve in a given solvent Saturated solution: a solution where no more solute can dissolve (if you add too much sugar to water, it won’t dissolve, it just clumps together at the bottom of the glass) Unsaturated solution: a solution that has not reached the limit of solute that will dissolve Concentration of solution = amount of solute/amount of solution (g/mL) Note the amount of solution, NOT solvent

Concentration of a Solution If a sample contains 150 g of sugar in 100 mL of water, what is the concentration? 1.5 g/mL If a sample contains 200 g of sugar in 100 mL of water, what is the concentration? 2.0 g/mL We would say that the first solution is more dilute, and the second solution is more concentrated

Molarity Refers to the number of solute particles in a solution The number of moles in a solute tells you how many molecules are present Molarity (M) = number of moles of solute / liters of solution Example: if I have a solution that has 2 moles of solute per every 1 liter of solution, what is the molarity? 2 M (2 moles of solute divided my 1 liter of solution)

Solubility The solubility of a solute is its ability to dissolve in a solvent If a solute can dissolve within a solvent, then it is said to be soluble in that solvent Like dissolves like—polar solutes dissolve in polar solvents, nonpolar solutes dissolve in nonpolar solvents A solute that does not dissolve in a solvent is said to be insoluble in that solvent Sand is insoluble in water, but it is soluble in hydrofluoric acid Styrofoam is insoluble in water, but it is soluble in acetone (nail polish remover)

Solubility Trends At higher temperatures, solubility of water-soluble solids increases—it is easier for different solutes to dissolve at higher temperatures than it is at lower. Sugar will dissolve more quickly in hot water than it does in cold water The solubility of gases in liquids decreases at higher temperatures At higher pressure, the solubility of a gas in a liquid increases Carbon dioxide molecules dissolve into soda pop because they are under great pressure from the tightly unopened lid

Soap is both Polar and Nonpolar Soap molecules have both nonpolar and polar properties Typically have a long nonpolar tail of carbon and hydrogen atoms and a polar head containing at least one ionic bond

How soap works Dirt and grease mixed together make grime—contains many nonpolar components Most of the soap molecule is nonpolar, so it will attract the nonpolar grime molecules by induced dipole-induced dipole interactions Molecules of soap will surround itself around a particle of grime—this is called a micelle This attraction will lift grime off the surface it is on