Chapter 16- Solutions

Solutions Homogeneous mixtures Can be solid, liquid, or gaseous Contains: Solute: dissolved particles in a solution Solvent: dissolving medium in a solution Solute + solvent = solution Ex: Sodium chloride dissolving in water NaCl = soluteH 2 O= solvent

Dissolving The compositions of the solute and the solvent determine whether or not a substance will dissolve. Other factors determine how fast a substance dissolves.

Factors that influence time 1.) Agitation (stirring/shaking)- brings fresh solvent in contact with the surface of the solute. 2.) Temperature- with higher kinetic energy there will be an increase in the number of collisions. 3.) Particle size- smaller size will dissolve faster.

Solubility Amount of solute that dissolves in a given amount of a solvent at a given temperature and pressure Represents a saturated solution Normally expressed in grams of solute per 100 grams of solvent

Types of solutions 1.) Saturated- contains the maximum amount of solute for a given amount of solvent at a constant temperature. 2.) Unsaturated- contains less solute than a saturated solution at a given temperature. 3.) Supersaturated- contains more solute than it can theoretically hold at a given temperature. (very unstable)

Solubility Curve What happens to the solubility of KNO 3 as temperature increases? What is the solubility of KBr at 80 degrees Celsius?

Factors that Affect Solubility 1.) Temperature Solubility of most ionic compounds increase as temperature increases Solubility of gases decrease as temperature increases 2.) Pressure (only applies to gases) Henry’s law- at a given temperature, the solubility of a gas is directly proportional to the pressure of the gas above the liquid. (As P , S  )

Concentration A measure of the amount of solute that is dissolved in a given quantity of solution. Concentrated vs. Dilute Relative terms Concentrated contains large amts. of solute Dilute contains small amts. of solute

Molarity (M) Note: the symbol is a capital M Ex: 12M HCl- 12 molar HCl (concentrated) vs. 0.1 M HCl- 0.1 molar HCl (diluted) Molarity = moles of solute Liters of solution

Example #1 What is the molarity of a 500 mL solution containing 3.0 mol of NaCl?

Example #2 Calculate the molarity of a 2.4 L solution containing 50.5 g of CaCl 2.

Example #3 How many moles of KBr are there in a 0.25 M solution with a volume of 600 mL?

Example #4 How many grams of HCl are in a 735 mL solution that has a concentration of 1.0 M?

Dilutions Add more solvent without the addition of more solute M 1 V 1 = M 2 V 2 1 refers to the situation before dilution and 2 refers to the situation after dilution

Example #1 A stock solution of 1.00 M NaCl is available. How many milliliters are needed to make mL of M solution?

Example #2 Concentrated HCl is 12.0 M. What volume is needed to make 2.00 L of 1.00 M solution?

Example #3 A stock solution of 10.0 M NaOH is prepared. From this solution, you need to make mL of M solution. How many mL will be required?