CHEM 120: Introduction to Inorganic Chemistry

1
CHEM 120 Introduction to Inorganic Chemistry

• Instructor Upali Siriwardane (Ph.D., Ohio State
  University)
• CTH 311, Tele 257-4941, e-mail
  upali_at_chem.latech.edu
• Office hours 1000 to 1200 Tu Th 800-900
  and 1100-1200 M,W, F

2
Chapters Covered and Test dates

• Tests will be given in regular class periods 
  from  930-1045 a.m. on the following days
• September 22,     2004 (Test 1) Chapters 1 2
• October 8,         2004(Test 2)  Chapters  3,
  4
• October 20,         2004 (Test 3) Chapter  5 6
  
• November 3,        2004 (Test 4) Chapter  7 8
• November 15,      2004 (Test 5) Chapter  9 10
• November 17,      2004 MAKE-UP Comprehensive
  test (Covers all chapters
• Grading
• ( Test 1 Test 2 Test3 Test4 Test5)
  x.70 Homework quiz average x 0.30 Final
  Average
•                               5

3
Chapter 7 Reactions and Solutions

• 1. Types of chemical reactions combination,
  decomposition, or replacement.
• 2. Classes of chemical reactions precipitation,
  reactions with oxygen, acidbase, and
  oxidationreduction.
• 3. Solution terms solution, solute, and solvent.
  
• 4. Kinds of solutions gas/liquid, liquid/
  liquid, solid/liquid
• 5. Solubility and equilibrium.
• 6. Solution concentration weight/volume percent
  and weight/weight percent.
• 7. Solution concentration molarity.
• 8. Dilution Preparing solutions.
• 9. Interconvert molar concentration of ions and
  illiequivalents/liter.
• 10. Concentration-dependent solution properties
  Collegative properties.
• 11. Unique chemical and physical properties of
  water.
• 12. Role of electrolytes in blood and their
  relationship to the process of dialysis.

4
Writing chemical reactions

• We can classify some chemical reactions according
  to certain patterns that are observed. This helps
  us to predict the products of reactions.

5
Combination reactions

• Combination Reaction

6
Decomposition reactions
7
Replacement reactions single replacement
8
Replacement reactions double replacement

9
Classify as to type of reaction

• 2Al(OH)3(s) g Al2O3(s) 3H2O(g)
• Fe2S3(s) g 2Fe(s) 3S(s)
• Na2CO3(aq) BaCl2(aq) g BaCO3(s) NaCl(aq)
• C(s) O2(g) g CO2(g)

10
Types of chemical reactions

• Precipitation reactions mix reactants together
  and get an insoluble precipitate (not soluble in
  water).
• How do you know what cmpds are insoluble?
• Learn table 7.1

11

• 1A salts, NO3-s, acetates (CH3COO-), NH4s are
  very soluble.
• Cl-s, Br-s and I-s are soluble except when
  combined with Ag, Pb2, Hg22.
• CO32-s, PO43-s, S 2-s generally insoluble
  (except for 1As and NH4)
• OH-s Ba2, 1As are soluble others generally
  insoluble
• The SO42-s of Ba2, Ag, Ca2, Sr2, Pb2are
  insoluble. Others are soluble.

12
Are these soluble?

• Ag2SO4
• Li2S
• Pb(NO3)2
• AgCl
• BaSO4
• (NH4)2SO4

13
Predict whether get precipitation when mix

• Zinc sulfate and barium chloride
• Sodium sulfate and potassium chloride)
• Ammonium carbonate and calcium chloride
• Strontium nitrate and potassium phosphate

14
Reactions with oxygen

• Combustion Reactions When compounds containing C
  and H react with O2 (burning or combustion) get
  CO2 and H2O. (Greenhouse effect)
• Corrosion 4Fe(s) 3O2(g) g 2Fe2O3(s)
  rust

15
Acid-base reactions

• Acid-base reactions involve transfer of a H from
  the acid (starts with H) to the base (hydroxide)
  to form a salt and water
• Oxidation-reduction will be covered in Chapter 9

16
Properties of solutions

• A solution is a homogeneous mixture of two or
  more substances and is made up of a solvent and
  one or more solutes.
• The solutes are the species that are being
  dissolved in the solvent. The solvent is usually
  present in the greater amt.
• An aqueous solution has ________ as the the
  solvent.

17
Types of solutions

• gas in gas --air
• gas in liquid--soda
• gas in solid--gas on solid catalyst
• liquid in liquid
• liquid in solid--mercury amalgam
• solid in liquid
• solid in solid--14-karat gold

18

• Ionic compounds (electrolytes) dissociate into
  ions when dissolved in water. The solutions
  conduct electricity.
• Molecular compounds in general do not dissociate
  into ions in aqueous solution. The solutions do
  not conduct electricity and are
  ________________.

19
Properties of solutions

• 1. A solution is a ___________ mixture. Each
  species in the solution
• 2. retains its ________ identity.
• 3. __________composition
• 4.clear and transparent (but can have color)
• 5. remains uniform throughout for all time
• 6. can be separated into its components by
  ___________ means.

20

• Solute size is _________________.
• The solute cannot be separated from the solvent
  by paper filtration.

21
Colloids (colloidal suspension)

• Colloids have similar properties as solutions
  but the particle size is
• Colloids behave differently when exposed to
  light.
• ________ effect helps distinguish between
  solutions and colloids.
• Homogenized milk is a _____________.

22
Emulsions and Suspensions

• Emulsions, suspensions larger particle size than
  solutions. Solute separates on standing.
• Particle size is gt 200nm.
• Filterable.

23
Degree of solubility

• Can dissolve different amounts of solute in
  solvent.
• Maximum amount of solute that can be dissolved in
  a given amt of solvent at a given
  temp____________

24

• Say a solution is __________ if the maximum
  amount of solute is dissolved in a given solvent.
  
• Solid ?solution
• Dynamic equilibrium set up between dissolved and
  undissolved solute
• Maximum amout of solute that can be dissolved in
  a given amt of solvent at a given temp
  solubility

25

• If a solution has less than the max amt
  dissolved
• If a solution has more than the max amount
  dissolved ______________ unstable--excess
  solute will fall to bottom and form a
  precipitate.

26
Factors that affect solubility

• Like dissolves like--smaller difference in
  polarity between solute and solvent, more
  soluble.
• Polar solutes in polar solvents
• Non-polar solutes in non-polar solvents
• Ionic solids in polar solvents

27
Factors that affect solubility

• I. Temperature
• A. ionic compound in water
• B. Gas in water

28
Factors that affect solubility

• II. Pressure
• A. Pressure changes have little effect on the
  solubility of a solid or liquid in another
  liquid.

29
Pressure effects continued

• B. The solubility of a gas in a liquid

30

• Under 1 atm total pressure, the partial pressure
  of O2 is 159 mmHg and the solubility of O2 in
  blood is 44g/100mL.
• In Denver (mile high city) PO2 132mmHg and the
  solubility of O2 in the blood is 37g/100mL
• Mt Whitney (2.5miles high) PO2 98 mmHg and the
  solubility of O2 in the blood is 27g/100mL
• Mt Everest (5.8 miles) PO2 52 mmHg and the
  solubility of O2 in the blood is 14g/100mL

31
Problem

• The solubility of N2 in blood at 37oC and at a
  partial pressure of 0.80 atm is 5.6 x 10-4 mol/L.
• A deep sea diver breathes compressed air with the
  partial pressure of N2 equal to 4.0 atm. How much
  N2 is dissolved in the blood at this pressure?

32
Concentration of solutions

• Concentration gives us the amount of solute
  dissolved in a given amt of solvent or in a given
  amt of solution.
• There are different ways of expressing
  concentration.

33
Percent (W/V )

• Weight/volume percent
• weight/volume (W/V)
• (mass of solute in g? vol of soln in mL) x 100
• Note that the volume of a solution does not
  equal the volume of solute and solvent.

34
Percent (W/W)

• Weight/weight percent
• Weight/weight (W/W) (mass of solute
  ??mass of solution) x 100
• The mass of the solution

35
Problems

• Calc the composition of the soln in W/V 20.0g
  acetic acid in 2.50L sollution
• Calc the W/W of 31.0 g of KCl in 152 g of
  water.
• Calc the W/W of 50.0 g KCl in 5.00 x 102 mL
  solution (d 1.14g/mL)

36

• How many grams of solute are needed to prepare
• A. 2.50 x 102 g of 5.00 (W/W) NH4Cl
• B. 2.50 x 102 mL of 3.50 (W/V) Na2CO3
• Calc the amount of water that must be added to
  5.00 g of urea (NH2)2CO in the preparation of a
  16.2 W/W by mass solution.

37
Molarity M

• Molarity (M) moles of solute ??vol of soln in L
• units of molarity mol of solute/L solution
• M moles solute(M )/V and moles M x V
• Molarity and W/V are temperature dependent.

38
Molarity problems

• Calc the molarity of 20.0g acetic acid in 2.50L
  solution.
• Calc the no of grams of solute needed to make
  2.50 x 102 mL of 0.200M KOH.
• Calc the volume, in ml, needed to provide 2.14g
  of NaCl from a 0.270M solution.

39
Dilution

• When a solution is diluted you add more solvent.
  The no. of moles of solute does not change.
  (moles M x V)
• So initial vol x molarity (mol/L) mol solute
  and final vol x new molarity same moles
  moli molf
• So MiVi MfVf

40
Dilution problems

• 50.0mL of a 0.250M sucrose soln was diluted to
  5.00 x 102 mL. What is the molar conc of the
  resulting solution?
• A 6.00 mL portion of an 8.00M stock solution is
  to be diluted to 0.400M. What will be the final
  volume after dilution?

41
Molality (m)

• molality (m) moles of solute/mass in kg of
  solvent
• A 2.5m (molal) NaCl solution has 2.5moles of NaCl
  dissolved in 1000g or 1kg of solvent
• Molality is temperature independent.

42
Concentration-dependent solution properties

• Colligative properties are properties

43

• So NaCl(aq) g Na (aq) Cl-(aq)
• K2SO4(aq) g 2K(aq) SO42-(aq)
• C12H22O11(aq) g C12H22O11(aq)

44

• We are going to examine the effect of adding a
  solute to a solvent on
• 1. vapor pressure
• 2. freezing point
• 3. boiling point
• 4. osmosis
• Remember that colligative properties depend only
  on the number of particles in solution and not on
  their identity.

45
Vapor pressure

• When a solute is added to a solvent the vapor
  pressure (equilibrium) of the solution is lower
  than that of the pure solvent. (explain)
• Raoult observed the relationship between the
  amount of the solvent and the vapor pressure of
  the solution

46
Effects on freezing and boiling points

• What effect does vp lowering have on the freezing
  pt and boiling pt of a solution?
• Since the vapor pressure of the solution is lower
  than the vapor pressure of the pure solvent,

47

• When a nonvolatile solute is added to a solvent
  the freezing point of the solution is lowered.
  (explain)

48
Math relationship for b.pt. elevation and f. pt
depression

• Dtf I mkf kf is the freezing pt constant
• i no of particles in solution per formula unit
• For molecular species i 1
• For NaCl i These i values
• For K2SO4 i assume 100
• For Al2(SO4)3 i ionization.
• For water kf 1.86oC/m

49

• Dtb imkb kb is the b. pt. constant m is
  the molality of the solution and i is the no. of
  particles in solution.
• For water kb 0.52oC/m

50

• What are the normal freezing and boiling pts of
• a. 58.5g NaCl in 100. g of water
• b. 60.0 of urea (NH2)2CO in 100. g of water.

51
Osmosis

• Certain materials allow passage of molecules of a
  certain size through but not bigger molecules.
  These are called __________________ membranes.
• When have pure solvent and a solution separated
  by a semipermeable membrane (or 2 solutions of
  different concentrations), nature wants the
  concentrations in the 2 sides to be the same.

52

• So the solvent moves from the less concentrated
  to the more concentrated side to try to make the
  concs of the 2 solns the same. Process is called
• Osmotic pressure (p) is the

53
lighter color is less concentrated solution
0.15M NaCl vs HOH p7.3 atm (HOH column 250 ft
high)
54

• p I MRT where M is the molarity of the soln R
  0.0821 L atm/Kmol and T is the temp in Kelvin
• Have to remember that osmosis is a colligative
  property and depends on the no of particles in
  solution and not their identity.

55
isotonic soln hypotonic soln
hypertonic soln
more dilute than more conc
than cell--hemolysis
cell--crenation
Same conc
56

• Blood 0.30M on particles
• 0.90 saline and 5.0 glucose are also 0.30 M
  --isotonic with blood (intracellular fluids)

57
Osmosis problems

• Calc the osmotic pressure of 0.50M NaCl and 0.50M
  sucrose. Assume a temp of 25oC.

58
Compare 0.50M NaCl and 0.50M Sucrose

• Which has higher m. pt?
• Which has higher b. pt?
• Which has higher vapor pressure?
• Each solution is separated from water by a
  semipermeable membrane. Which solution has the
  higher osmotic pressure?