Lectures 13

1
Lectures 1-3

• Introduction - Review of Key General Chemistry
  Concepts

2
Naming Chemical Compounds

• ammonium chloride
• ferrous sulfate
• mercurous chloride
• sodium bicarbonate
• ferric oxide
• hydrofluoric acid
• potassium permanganate

3
Grading Rubric

• O if compound correctly named
• C if correct cation symbol
• IC if incorrect cation symbol
• A if correct anion symbol
• IA if incorrect anion symbol
• S if incorrect stoichiometry of cations and
  anions represented

• High IC and/or IA implies need to learn element
  symbols
• High C and A indicates good handle on element
  symbols
• High S implies need to learn
• Cation/anion charges
• How to name compounds
• High O keep up the good work!

4
Naming Chemical Compounds

• ammonium chloride NH4Cl
• ferrous sulfate FeSO4
• mercurous chloride Hg2Cl2
• sodium bicarbonate NaHCO3
• ferric oxide Fe2O3
• hydrofluoric acid HF
• potassium permanganate KMnO4

5
Being Able to Name Compounds is Very Important

• PLEASE!!! Learn to do this now
• Study!
• Active practice
• Build up
• Cations/Anions
• Naming Compounds

6
First Step

• Learn the symbols and charges for the common
  inorganic elements
• The charge on some metals can be discerned by
  their group name
• All elements in Group 1A have a 1
  chargeexamplesLi, Na, K
• All elements in Group 2A have a 2
  chargeexamplesMg2, Ca2, Ba2

7
Some Metals Have Several Common Oxidation States

• Ironferrous, Fe2ferric, Fe3
• Coppercuprous, Cucupric, Cu2

• Mercurymercurous, Hg22mercuric, Hg2

8
Naming Cations - Endings

• -ous lower oxidation state
• -ic higher oxidation state
• NB -ous, -ic do NOT signal a specific numerical
  value of a cations charge

9
Some Metals Have Several Common Oxidation States

• Ironferrous, Fe2ferric, Fe3
• Coppercuprous, Cucupric, Cu2

• Mercurymercurous, Hg22mercuric, Hg2

10
Ammonia vs. Ammonium

• Ammonia, NH3, is a compoundCompounds are neutral
• Ammonium, NH4, is a cation

11
Anions - Require Some Effort to Learn

• Sulfate, SO42-
• Sulfite, SO32-
• Nitrate, NO3-
• Nitrite, NO2-
• Phosphate, PO43-

• Acetate, C2H3O2-
• Oxalate, C2O42-
• Chromate, CrO42-
• Dichromate, Cr2O72-
• Carbonate, CO32-
• Bicarbonate, HCO3-

12
More Anions

• Iodate, IO3-
• Permanganate, MnO4-
• Thiocyanate, SCN-
• Hydroxide, OH-

13
Naming Complex Anions

• Nitrite, NO2-
• Nitrate, NO3-

14
Naming Common Anions

• Sulfide, S2-
• Sulfite, SO32-
• Sulfate, SO42-

15
Naming Common Anions

• Chloride, Cl-
• Chlorate, ClO3-
• Perchlorate, ClO4-

16
Naming Common Anions

• Chromate, CrO42-
• Dichromate, Cr2O72-

17
Naming Common Anions

• Iodide, I-
• Iodate, IO3-

18
Naming Common Anions

• Bicarbonate, HCO3-
• Acetate, C2H3O2- (CH3CO2-)
• Oxalate, C2O42-

19
Naming Chemical Compounds

• Cation usually goes first Cationa Anionbexcept
  when this ordering implies incorrect bonding
  arrangement (e.g., organic compounds)
• Compound must be neutral (have no net charge)
• So, sum of cation and anion charges zero

20
Doe-See-Doe Rule

• Cationb Aniona- gt Compound
• (CationaAnionb)
• Why? (ab)-(ba) 0
• Note when a and b are gt1, use lowest common
  denominator

21
Example

• Ferric oxide
• Step 1 Identify cation and charge
• Fe3
• Step 2 Identify anion and charge
• O2-
• Step 3 Determine stoichiometryFe2O3

22
Naming Acids

• Definition proton donor (Bronsted-Lowry)
• HA H A-
• Hydrochloric acid HCl
• Perchloric acid HClO4
• Nitric acid HNO3
• Sulfuric acid H2SO4

23
Organic Acids

• RCOOH RCOO- H
• Carboxylic acids
• Formic acid HCOOH
• Acetic acid HC2H3O2 (H3CCOOH)
• Oxalic acid H2C2O4 (HOOCCOOH)

24
Bottom Line Naming Compounds

• Takes effort!
• There are no short cuts - bite the bullet and
  memorize common anions and cations and practice,
  practice, practice
• Make flash cards and quiz yourself
• Complete Assignment 0 in Problem Solver
• Use Webquizzer

25
Systeme Internationale (SI)

• Fundamental measurements based on
• length meter, m
• mass gram, g
• volume liter, L

26
Common Prefixes for Units

• kilo- k 103
• centi- c10-2
• milli- m10-3
• micro- ?10-6
• nano- n10-9
• pico- p10-12

27
Moles The Fundamental Unit of Currency in
Chemistry

• Only moles can be used to relate quantities of
  different chemicals
• Mole Avogadros of molecules g /
  Formula Weight
• Moles Euro

28
Example

• An American travels to the Netherlands and then
  to the UK
• Dollars ? Euros ? Pounds
• Chloride compound reacted with AgNO3 and
  converted to AgCl
• g Cl- ? moles Cl- ?moles AgCl ?g AgCl

29
Formula Weight

• FW weight in g of Avogadros of molecules of
  any element or compound
• For element, FW atomic weight
• For compound AbCd FW b(atomic weight of A)
  d(atomic weight of C)

30
Example of Calculation of FW

• What is the FW of barium hydroxide?
• AnsBa(OH)2137.2 (216) 21.008) 171.2
  g/mole

31
Commonly Used Units of Concn

• Molarity, M - university
• Normality, N - real world

32
CHM 1221 Introduction (contd)

• Moles
• Formula Weight (FW)
• Molarity
• Normality

33
Molarity

• Fundamental unit of concentration
• units M/L
• Definition moles solute / liters solutionM
  moles/volume (g/FW)/volume

34
Problem

• How many grams of ferrous ammonium sulfate
  hexahydrate (FW 392.14) are required to prepare 2
  L of an 0.45 M solution?
• ANS 352.9 g

35
Normality

• Units equiv/L
• Definition N M nor N/n Mwhere n
  moles e-s or Hs

36
Example

• What is the normality of a 2 M solution of
  sulfuric acid?
• H2SO4 produces 2 moles Hs /mole H2SO4 so n 2
• Therefore, N M n 2 M 2 4 N
• NB N gt M

37
Reading Reactions - Rules

• Read left to right
• A B CA and B react to form C, i.e.,A
  and B are reactantsC is a productReactants
  Products

38
Chemical Reactions - 2 Types

• Reactions that go to completionA B ? C
• Equilibria reactionsA B C

39
Coefficients Tell Stoichiometry

• A B 2Csays1 mole of A and 1 mole
  of B react to produce 2 moles of C
• NB1 always moles (think Euro)
• NB2 if no number, 1 is understood

40
Predicting Reactions

• Acid-BaseAcid Base Salt water
• Break up reactants into cations and anions and
  switch partnersHCl NaOH -gt ???

41
Limiting Reagent

• Reactant present insmallest amount which limits
  the extent of a chemical reaction
• 1 cat head 1 cat body 1 catso the body is
  the limiting reagent

42
Example

• 50 mL of 0.1 M NaOH are combined with 10 mL of
  0.2 M HCl. How many moles of NaCl are produced?
• ANS 2 mmoles NaCl

43
Example - contd

• First write the balanced reactionNaOH HCl
  NaCl H2OThis tells us 1 mole of NaOH reacts
  with 1 mole HCl
• We have 5 mmoles NaOH 2 mmole HCl

44
Example - contd

• Since only 2 mmole of HCl can react with 2 mmole
  NaOH so NaOH is the limiting reagent
• Since 1 mole NaCl produced per mole HCl consumed,
  2 mmole NaCl produced

45
In Dilute Aqueous Solution

• ppm (part-per-million) 1 mg/ L
• ppb (part-per-billion) 1 ?g/L
• Note both assume density of water

46
Problem

• a) Calculate the molarity of a 2 ppb solution of
  sodium chloride (FW 58.5). b) Express the
  concentration in nM.
• ANS a) 3.42 x 10-8 M b) 34.2 nM

47
Problem

• 2 ppb 2 ?g/L NaCl2 x 10-6 g NaCl / L mole/
  58.5 g 3.42 x 10-8 M
• since nmole 10-9 mole,
• 3.42 x 10-8 mole/L nmole/10-9 mole 34.2 nM

48
Dilution

• Often practically easier to prepare a stock
  solution and use this to make a less concentrated
  solution

Final solution
Original solution
49
Dilution
Moles taken
Moles final
2
1

• key relationship M1V1 M2V2where M1 is
  initial molarity, V1 is volume transferred, M2 is
  final molarity, and V2 is final volume
• note moles removed from stock solution (M1V1)
  must equal moles in final solution (M2V2)

50
Example

• 10 mL of a 5 mM solution of ferrous nitrate are
  transferred to a 250 mL volumetric flask. What
  is the concentration of ferrous nitrate in the
  diluted solution?
• ANS 2 x 10-4 M

51
Example

• moles taken M1 V1 0.01 L 0.005 moles/L 5
  x 10-5 moles M2 V2 M2 0.25 L
• so, M2 5 x 10-5 moles / 0.25 L 2 x 10-4 M

52
Classification Scheme for Analytical Methods

• Amount of analyte
• Size of Sample

53
Classification by Amount of Analyte

• Major - analyte represents gt 1 of sample
• Minor - analyte represents 0.1 - 1 sample
• Trace - analyte represents lt 0.1 sample

54
Classification by Size of Sample