Title: Solutions
1Chapter 9
2Mixtures and Solutions
3Mixtures and Solutions
- Mixtures
- Heterogenous mixture can be viewed as different
regions - Homogenous mixing is uniform
- Solutions
- Colloids
- Mixtures occur in all phases of matter
4Mixtures and Solutions
- Most common form is a gas or solid dissolved in a
liquid. - Solute - Dissolved substance (solid or gas)
- Solvent Liquid the solid is dissolved into.
5The Solution Process
A good rule of thumb for predicting solubility
is that like dissolves like.
6The Solution Process
7Solid Hydrates
- Solid hydrates - ionic compounds that attract
water strongly enough to hold onto water
molecules even when crystalline - Hygroscopic pull water out of the air to
incorporate it into the crystalline structure - Representation
8Solubility
- To form a solution we follow the adage like
dissolves like, but substances have differing
degrees to which they will dissolve into solution - Solubility
- Can be described by the equilibrium constant for
a substance - Two solutions that are entirely soluble in each
other (like forces) Miscible - Most substances reach the limit of a saturated
solution A solution that contains the maximum
amount of dissolved solute at equilibrium.
9The Effect of Temperature on Solubility
- Chapter 7 Equilibrium constant effected by
temperature - Solubility of a substance is also effected by
temperature - Most solid substances become more soluble as
temperature rises. - The solubility of gases decreases as temperature
rises.
10The Effect of Pressure on Solubility
Henrys law The solubility of a gas is directly
proportional to its partial pressure. If T is
constant, C ? Pgas , or C/Pgas k , or C1/P1
C2/P2 .
11Units of Concentration
- Solute A substance dissolved in a liquid.
- Solvent The liquid in which a substance is
dissolved. - Solution The combination of solute and solvent.
- A very useful means of expressing concentration
in the laboratory is molarity (M), the number of
moles of solute dissolved per liter of solution.
12- Weight/Volume Percent Concentration (w/v)
- Mathematically, (w/v) concentration is found by
taking the number of grams of solute per
milliliters of solution and multiplying by 100. - Volume/Volume Percent Concentration (v/v)
- Mathematically (v/v) is determined from the
volume of solute (usually in mL) per milliliter
of solution multiplied by 100.
13 Parts per Million (ppm) and Parts per Billion
(ppb) When concentrations are very small, as
often occurs in dealing with trace amount of
pollutants or contaminants, parts per million
(ppm) or parts per billion (ppb) units are used.
14- To prepare 100 mL of a specific solution, the
solute is measured out and dissolved in just
enough solvent to give a final volume of 100 mL. - If the solute were dissolved in 100 mL of
solvent, the final volume of the solution will
likely be a bit larger or smaller than 100 mL.
15Dilution
- Dilution Lowering concentration by adding
additional solvent. - Dilution factor The ratio of the initial and
final solution volumes (V1/V2). - In the dilution process, the amount of solute
remains constant, only the volume is increased. - Moles of solute M1V1 M2V2 constant
- Dilution equations can be generalized to other
concentration units, C1V1 C2V2
16Ions in Solution Electrolytes
- Electrolyte A substance that produces ions and
therefore conducts electricity when dissolved in
water. - Strong electrolyte A substance that ionizes
completely when dissolved in water. - Weak electrolyte A substance that is only partly
ionized in water. - Nonelectrolyte A substance that does not produce
ions when dissolved in water.
17Properties of Solutions
- Most properties of a solution are similar to that
of a pure solvent but some properties, known as
colligative properties, are very different. - Vapor pressure is lower for solutions
- Boiling point is higher for solutions
- Freezing point is lower for solutions
18Optional Homework
- Text 9.32, 9.33, 9.34, 9.42, 9.50, 9.54, 9.60,
9.62, 9.64, 9.66, 9.70, 9.72, 9.82, 9.100, 9.102 - Chapter 9 Homework from the website
19Required Homework