Chapter 22 Solutions Lesson 2

A. Concentration 1. Concentrated solution 2. Dilute solution large amount of solute 2. Dilute solution small amount of solute

3. Concentrations of solutions can be described as a percent – the ratio of solute to solution.

Concentration Problems % by Volume or % v/v A solution is made by adding water to 50 mL of methanol until the final volume of the solution was 300 mL. What is the percent by volume of the methanol in this solution?

Concentration Problems % by Volume or % v/v A solution is made by adding 35 mL of ethanol to 65 ml of water. What is the percent volume of the ethanol?

Concentration Problems % by Mass or % m/m 1g H2O = 1 mL What is the mass percent of NaCl if 5 grams of NaCl is added to 95 grams of water.

Concentration Problems % by Mass or % m/m 1g H2O = 1 mL If I make a solution by adding 83 grams of NaOH to 750 mL of water… What is the percent mass of NaOH in this solution?

Diluting a Solution Problems Whether it's in your house, your office, or a scientist's lab, storage space is often hard to come by and very precious. Just like you and the cleaning supplies that are probably hidden under your kitchen sink, making the cupboard overflow, scientists often have cupboards overflowing with chemicals. Just like you, they find it easier to keep liquids in a concentrated form, called a stock solution, because it takes up less room. Then scientists dilute the solutions to the needed concentration at the time of use. Knowing how to dilute a solution is an important concept to learn.

Diluting a Solution Problems Equation for diluting a solution M1V1 = M2V2 If I add water to 100 mL of a 0.15 M NaOH solution until the final volume is 150 mL, what will the concentration of the diluted solution be?

Diluting a Solution Problems Equation for diluting a solution M1V1 = M2V2 How much water would I need to add to 500 mL of a 2.4 M KCl solution to make a 1.0 M solution?

Diluting a Solution Problems Equation for diluting a solution M1V1 = M2V2 Pretend you are doing a lab experiment that requires 3 L of a 0.5 M solution of HCl. Your stock solution is 10 M. How much stock solution do you need to add to water to make the needed solution?

B. Solubility 1. Solubility maximum grams of solute that will dissolve in 100 mL of solvent at a given temperature a. varies with temperature b. varies with different types of substances

Comparing Solubilities 1. The amount of a substance that can dissolve in a solvent depends on the nature of these substances. 2. In one beaker, 1 g of solute A dissolves completely, but additional solute does not dissolve and falls to the bottom of the beaker.

3. 1 g of solute B dissolves completely, and two more grams also dissolve before solute begins to fall to the bottom. 4. If the temperature of the water is the same in both beakers; you can conclude that substance B is more soluble than substance A.

C. Solubility Curves Each line on the graph is called a solubility curve for a particular substance. 2. Solids are more soluble at... high temperatures. 3. Gases are more soluble at... -low temperatures

D. Types of Solutions A saturated solution is a solution that contains all the solute it can hold at a given temperature.

This table shows the amounts of a few solutes that can dissolve in 100 g of water at different temperatures, forming saturated solutions.

2. An unsaturated solution is any solution that can dissolve more solute at a given temperature a. Each time a saturated solution is heated to a higher temperature, it becomes unsaturated.

Supersaturated Solutions 3. A supersaturated solution is one that contains more solute than a saturated solution at the same temperature a. Supersaturated solutions are unstable.

b. For example, if a seed crystal of sodium acetate is dropped into the supersaturated solution, excess sodium acetate crystallizes out.

Concentration UNSATURATED SOLUTION more solute dissolves no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form