CHEM 1405

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CHEM 1405

• Class Meeting 18

2
Assignments and Reminders

• Reading Assignment
• Chapter 8 by Thursday
• Homework Problems due Today Thursday Mar 23rd
• Chapter 7 Problems 3, 4, 6, 8, 9,10, 11, 12,
  15,16,17,20,22
• Homework Problems due Thursday Mar 30th
• Chapter 8 Problems 1 through 29 except 3 and
  4
• Class website
  http//iws.ccccd.edu/jstankus/

Please use only one side of the page when
submitting Homework
3
Chemistry Help Resources

• My office hours
• Tuesdays after class in Lecture room
• Thursdays 1-2 in Math Lab
• Free Tutoring through college
• Students must submit a tutor request form in
  order to receive detailed information about the
  available tutoring services.  The form is
  available on Collin's website and in the
  following offices
• CPC room A108 (ask for Sonia Castillo)
• PRC room F109 (ask for Shontel Penny or Mary
  Eldridge)
• SCC rooms G200 and G141
• There are group tutoring services available for
  the following courses (SUBJECT TO CHANGE!)
• CHEM 1405, 1411, 1412, 2423,
•  
• Also available will be online tutoring in the
  following courses (SUBJECT TO CHANGE!)
• CHEM 1412 below

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Objectives

• 1.What is a solution? What are the different
  types of solutions?  
• 2.What is the difference between a soluble
  substance and a miscible substance?  
• 3.What is the difference between a saturated
  solution and a supersaturated solution?  
• 4.What factors determine the solubility of ionic
  compounds? Of covalent compounds?  
• 5.How do temperature and pressure affect the
  solubility of gases in water?

5
Solutions

• Solutions are homogeneous mixtures of two or more
  substances
• Homogeneous thoroughly mixed, even composition
  throughout
• Solute substance being dissolved
• Solvent substance doing the dissolving

6
Intermolecular Interaction and Solutions

• The same types of intermolecular interactions in
  solids and liquids occur in solutions

7
Intermolecular Interactions
8
Forces in Solution

• Like dissolves like
• Nonpolar compounds dissolve best in nonpolar
  solvents
• Oil and gasoline mix
• Polar compounds dissolve best in polar solvents
• Water and HCl mix

9
Solutions can be Liquids

• Salt water is a solution
• of sodium chloride
• dissolved in water
• Tap water is a solution of many trace minerals
  and dissolved gases in water

10
Solutions can be Gases

• Air is a solution of
• Oxygen
• Argon
• Water Vapor
• other trace gases
• Dissolved in nitrogen

11
Solutions can be solids
12
Solutes in solution

• A solid can be dissolved into a liquid
• Example NaCl (table salt) in water
• A liquid can be dissolved into another liquid
• Example Ethanol can be dissolved in water
• A gas can be dissolved into a liquid
• Example Carbon Dioxide (CO2) dissolved in water
  in carbonated beverages

13
Solutions can have multiple components

• Soft drinks are a solution
• Solutes
• Carbon Dioxide
• high fructose corn syrup (a solution of glucose
  and fructose)
• caramel color
• phosphoric acid
• caffeine
• citric acid
• natural flavors
• Solvent - Water

14
Solubility of Ionic Compounds

• Cations
• Positively charged ions
• Example Na
• Anions
• Negatively Charged ions
• Example Cl-

15
Dissolution of NaCl in water

• Movie Clip

16
Ionic Compounds in Solution

• Ions dissolve in water
• Charges on ions are attracted to partial charges
  on water

17
Ionic compounds in solution
18
Dynamic Equilibria

• Limit to how much solute can be dissolved
• Equilibrium between dissolving and precipitating

At equilibrium the solution is saturated
19
Aqueous Solution

• An aqueous solution has water as the solvent
• Most biologically relevant solutions are aqueous

20
Water Solubilities of Common Ionic Compounds

• Compounds that are soluble 
• Nitrates
• Acetates.
• Alkali metal (Group 1A) salts
• Ammonium salts.
• Compounds that are mostly soluble 
• Chlorides, bromides, and iodides
• except for those of Pb2, Ag, and Hg22.
• Sulfates,
• except for those of Sr2, Ba2, Pb2, and Hg22.
  
• Compounds that are mostly insoluble 
• Carbonates, hydroxides, phosphates, and sulfides,
  except for ammonium compounds and those of the
  Group 1A metals.

21
Solubility of Covalent Compounds

• Solubility dependent on intermolecular
  interactions
• Nonpolar compounds
• Dispersion forces
• Polar compounds
• Dipole-Dipole interactions
• Hydrogen bonding

22
Solubility of Covalent Compounds

• Like Dissolves like
• Nonpolar compounds dissolve nonpolar compounds
• Polar compounds dissolve polar compounds

23
Mixtures of liquids

• Miscible substances can be mixed in all
  proportions
• Immiscible substance do not mix

24
Quantities of Solutes in Solution

• A dilute solution is one that contains relatively
  little solute in a large quantity of solvent.
• A concentrated solution contains a relatively
  large amount of solute in a given quantity of
  solvent
• A saturated solution contains the maximum amount
  of solute that can be dissolved in a particular
  quantity of solvent at equilibrium at a given
  temperature.

25
Saturation Solubilities

• Curve gives maximum amount of solute dissolved at
  given temperature
• Most solubilities of ionic solids increase with
  Temperature

26
Supersaturated solutions

• A supersaturated solution contains more solute
  than is present in a saturated solution, with the
  excess solute remaining in solution
• The excess solute will precipitate out easily

27
Effect of Temperature on Gas Solubility

• Bubbles in heated water before boiling are the
  dissolved gasses coming out of solution

28
Effect of Pressure on Gas Solubility

• Solubility of gas in a liquid increases with gas
  pressure

29
Solubility of gases with pressure

• Keeping the cap on your soda increases the
  solubility of CO2 and keeps more in solution

30
Recrystallization

• Manipulation of solubilities can be used to help
  purify substances