Chapter 15: Solutions

Pages 452 - 483

• A solution is a homogeneous mixture.– Remember that homogeneous means all in the

same phase, you only see one thing.

A solution may exist as a solid, liquid or gas.To be considered a solution it must meet the following requirements:

1. Does not separate upon standing.2. Can not be filtered.3. Light passes through it unaltered.

• All solutions have two parts to them– Solute – the part of the solution that is being

dissolved or the smallest part of the solution.– Solvent – the part of the solution that does the

dissolving or the largest part of the solution.– It is possible for a solution to have more than one

solute, but usually only one solvent.• Two substances are said to be soluble or

miscible if they have like bonds.

“Likes dissolve Likes”.

• The process of a solution forming happens when solvent molecules attack and overcome the intermolecular forces holding the solute particles together.

• We say that the solute dissociates into ions or smaller particles.

• To overcome these intermolecular forces it helps for the solvent molecules to have similar intermolecular forces in their bonds.

• Factors Affecting Solution Formation– Types of Bonds: Ionic, Polar, Nonpolar Covalent– Size of Particle: Smaller dissolve easier than larger

particles.– Temperature: For most warmer temperatures aids

in solution formation. (Gases an exception)• Factors Affect how fast a solution forms

Stirring – provides more energy and collisionsTemperature – provides more energy &

collisionsParticle Size – smaller particles dissolve faster.

• Measuring the Concentration of a Solution– Concentrated: more solute , less solvent– Dilute: less solute, more solvent– Saturated: contains the most solute for a given

amount of solvent at a specific temperature.– Unsaturated: can dissolve more solute.

These are all qualitative measures of concentration, we will now look at some quantitative.

• One way to look at concentrations we have already used – Percent by Mass

• Another way that we really have been using is Molarity.

• 1 L = 1,000 mL (move the decimal point 3 places.)

• What is the percent of salt in a solution that is made by dissolving 35 grams of NaCl in 150 grams of water?

• If you have 250 grams of a solution that is 26% KCl, how many grams of KCl are dissolved in the solution?

• X = 65 g KCl

• What is the molarity of a solution that is made from dissolving 28 grams of HCl in enough water to make 0.35 L of solution?

• 28 grams HCl / 36 g/mol = 0.78 mol HCl

• How much water would you need to add to 18 grams of glucose, (C6H12O6), to make a 0.76 M solution?

• 18 g / 180 g/mol = 0.10 mol C6H12O6

• or enough water for 132 mL

Colligative Properties

• Adding a solute to a solvent will change some of the physical properties of the solvent.

• Adding an electrolyte can make the solution conduct electricity.

• Adding a solute will lower the freezing point of the solvent.

• Adding a solute will raise the boiling point of the solution.