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Solutions

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Most common form is a gas or solid dissolved in a liquid. ... form a solution we follow the adage 'like dissolves like,' but substances have ... – PowerPoint PPT presentation

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Title: Solutions


1
Chapter 9
  • Solutions

2
Mixtures and Solutions
3
Mixtures and Solutions
  • Mixtures
  • Heterogenous mixture can be viewed as different
    regions
  • Homogenous mixing is uniform
  • Solutions
  • Colloids
  • Mixtures occur in all phases of matter

4
Mixtures 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.

5
The Solution Process
A good rule of thumb for predicting solubility
is that like dissolves like.
6
The Solution Process
7
Solid 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

8
Solubility
  • 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.

9
The 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.

10
The 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 .
11
Units 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.

15
Dilution
  • 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

16
Ions 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.

17
Properties 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

18
Optional 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

19
Required Homework
  • Assignment 9
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