Solutions Mixtures Heterogenous Mixture substances that make up

Solutions Mixtures: - Heterogenous Mixture: substances that make up the mixture are not spread uniformly throughout the mixture. - Homogenous Mixture: components are uniformly spread throughout the mixture.

Solution: homogenous mixtures made of individual molecules, atoms, or ions. - Solute: the substance that is dissolved - Solvent: the substance in which the solute is dissolved - Aqueous Solutions: a solution in which water is the solvent

Solubility: the maximum quantity of solute that can be dissolved in a certain quantity of a solvent at a specific temperature. Factors that affect solubility: - The nature of the solute and solvent - Temperature: generally an increase in temperature increases the solubility of a solid solute - Pressure: pressure has no effect on the solubility of solids and liquids. For gases an increase in pressure increases solubility

Rate of Solution: how quickly a solid solute is dissolved by a solvent. Factors that determine the rate of solution: 1. The size of the particles 2. Stirring 3. The amount of solute already dissolved 4. Temperature

Dissolving: like dissolves like - Polar solvents dissolve polar solutes - Water is the polar solvent that is most commonly used to dissolve ionic compounds. Why? Hydrated ions: ions surrounded by water molecules Ionic solute Polar solute Nonpolar solute Na. Cl HCl Br 2

Changes in Energy When Dissolving a Solute - When a solid dissolves in a liquid it changes from a solid to a liquid. - This requires energy. Generally when dissolving a solid in a liquid is endothermic because it needs to take in heat to change from a solid to a liquid. - Exceptions are dissolving Na. OH and KOH

Strengths of Solutions: Dilute Solution: the amount of solute is small in relation to the amount of solvent. - Ex. Watered down Koolaid Concentrated Solution: when there is a relatively large amount of solute dissolved in an amount of solvent. - Ex. Really sugary Koolaid

- Saturated Solution: a solution that has dissolved all of the solute that it can normally hold at given conditions. - Solution equilibrium: the rate at which undissolved solute goes into solution is equal to the rate at which dissolved solute comes out of solution

Unsaturated Solution: a solution that contains less solute than it can hold at a certain temperature and pressure. Supersaturated Solution: a solution that can hold more solute than is present in its saturated solution. - This is very unstable. With just a slight change solute will fall out of solution. -Ex. Sodium Acetate

Solubility Curves: a graph that shows how much of a solute can be dissolved in a given amount of solvent over a range of temperatures.

Henry’s Law Gases are more soluble when they are under pressure. -Does a two liter of soda keep its carbonation better with the cap on or off? S 1 = S 2 S = Solubility P 1 P 2 P = Pressure The solubility of a gas is 0. 29 g/L at 263 k. Pa of pressure. What is the gas’s solubility at 136 k. Pa of pressure? S 1 = S 2 P 1 P 2 0. 29 g/L = S 2 263 k. Pa 136 k. Pa S 2 = 0. 15 g/L

Molarity: this is a way of describing the concentration of a solution with numbers. - The number of moles of solute in one liter of water. - Molarity (M) = moles of solute / liters of solution Problem: What is the molarity of a solution if I put 250 g of Na. OH in 1235 ml of water? M = moles of solute / liters of solution 250 g of Na. OH x 1 mole Na. OH = 6. 25 moles Na. OH 1 40 g of Na. OH M = 6. 25 moles Na. OH = 5. 06 M = 5. 1 M 1. 235 L

In a chemistry lab many times you have to make solutions from a stronger solution. - To calculate the amount of stronger solution you will need to dilute use this equation M 1 V 1 = M 2 V 2 - In this equation M is the molarity and V is the volume Problem: If I have to make 14 liters of 0. 2 M HCl of a lab, how many liters of a stock solution of 12 M HCl will I have to dilute? M 1 V 1 = M 2 V 2 12 M x V 1 = 0. 2 M x 14 L V = 0. 2 L

Molality: another way of describing the concentration of a solution using numbers. - Molality (m) = moles of solute / kg of solvent Problem: What is the molality of a solution that contains 48. 25 g of Na. Cl in 2586 ml of water? (assume that 1 ml of water = 1 g) m = moles of solute / kg of solvent 48. 25 g of Na. Cl x 1 mole of Na. Cl = 0. 825 moles Na. Cl 1 58. 5 g Na. Cl m = 0. 825 moles Na. Cl / 2. 586 kg of water = 0. 3189 m

Percent by volume: measuring the concentration of a solution by volume of solute and the volume of the solution - Percent by volume = volume of solute x 100% volume of solution Problem: If 10. 0 ml of acetone is diluted with water to a total volume of 200. 0 ml, what is the percent by volume of acetone in the solution? Percent by volume = volume of solute x 100% volume of solution Percent by volume = 10. 0 ml x 100% = 5. 00% 200. 0 ml

Percent by mass: measuring the concentration of a solution by the mass of the solute and the volume of the solution. - Percent by mass = mass of solute (g) x 100% volume of solution (ml) Problem: Calculate the grams of solute required to make 250 ml of 0. 10% Mg. SO 4. Percent by mass = mass of solute (g) x 100% volume of solution (ml) 0. 10% = mass of solute (g) x 100% 250 ml Mass of solute = 0. 25 g

Colligative Properties Making solutions changes three major colligative properties 1. Vapor pressure: vapor pressure is lowered when dissolving a solute in a solvent. - Vapor pressure is the ability for a liquid to change to a gas. - The more solute dissolved in a solution the more that solution will resist changing to a gas.

2. Boiling Point: boiling point is elevated when dissolving a solute in a solvent - Boiling point is the temperature where a liquid changes to a gas. - The more solute you dissolve in a solution the higher the boiling point will climb because the solute will help hold the solvent as a liquid.

3. Freezing Point: freezing point is depressed when dissolving a solute in a solvent - Freezing point is the temperature that a liquid changes to a solid. - The more solute dissolved by a solvent the lower the freezing point will fall because the solute gets in the way of the solvent crystallizing to form a solid.