Week 2/Th: Lecture Unit ‘4’ Symbols

© DJMorrissey, 2o12

Unit 3: Atomic Theory & Masses … -- nuclei, isotopes, nuclear mass -- elemental masses Unit 4: Molecules and Compounds -- nomenclature -- compounds and formulas -- polyatomic ions -- compound masses Unit 5: The Mole -- definition for counting, molar mass -- stoichiometry, balancing reactions Issues: (1) µ (Greek mu) for “ micro x10-6 ” (2) goof on blackboard Homework Set 1 closes on Saturday @ 08:00AM

Issues, Textbook Error

© DJMorrissey, 2o12

Gasoline in Windsor, Canada is selling for 1.259 CA$ / L, what is this in US$ / Gal? Facts: 1 Gal = 3.785 L , 1 US$ = 0.9885 CA$ = 1.259 CA$/L * 1 US$/0.9885 CA$ * 3.785 L/Gal = 4.8208 US$ / Gal

= 4.821 US$ / Gal (proper sig-fig)

Lower case English m stands for milli and 10-3

Lower case Greek µ stands for micro and 10-6

© DJMorrissey, 2o12

Week 2/Th: More Dimensional Analysis When you heat popcorn, it pops because water inside the kernel boils and then is released explosively when the shell can no longer sustain the internal pressure. Given that one kernel has a mass of 0.125 g before and only 0.106 g after popping. 1)  What percentage of its mass was lost during popping? = [mass lost / total mass ] *100 = [ (0.125-0.106) g / 0.125 g ] *100 = [0.019/0.125]*100 = 15 % (proper sig-fig) 1)  How many kernels are in a 1.00 pound bag of popcorn?

= 1.00 lb * 453.5924 g/lb *1 kernel/0.125 g = 3628.7392 kernels = 3.63x103 kernels (proper sig-fig)

Week 2/Th: Chemical Compounds

© DJMorrissey, 2o12

A compound comes from the combination of two or more elements in a fixed integer ratio. A compound can be obtained in a pure state and will have unique properties (melting pt., boiling pt., density, etc.) The “formula” is the ratio of atoms in the compound. The formula could use the smallest integers – called the empirical formula – or the ratio of integers in a single, whole molecule – called the molecular formula. These two formulas are the same in many simple molecules. The structural formula shows the bonding in a molecule. We can use the elemental masses given in the Periodic Table in chemical calculations of the formula mass or the molecular mass. -- more on this next week --

Week 2/Th: Compound Type & Nomenclature

© DJMorrissey, 2o12

We need a naming scheme for chemical compounds, but recall that there are two classes of compounds: Molecular compounds – the atoms are bonded together into a single independent unit (a molecule). Molecules are electrically neutral. The systematic name describes the atoms present. Exceptions are historical names and carbon compounds. Ionic compounds – a material that has two or more subunits that each carry an electrical charge, that can be separated or exchanged. The systematic name describes the subunits present. Memorization of subunits needed here – sorry!

Week 2/Th: Systematic Names

© DJMorrissey, 2o12

Molecular compounds – list the elements present, start with most reactive metals, end with most reactive non-metals. Use Greek prefixes for indicating the amount of each element Mono- Di- Tri- Tetra- Penta- Hexa-

CCl4 Carbon tetrachloride CO Carbon Monoxide CO2 Carbon Dioxide

Neutral combinations of N with O N2O Dinitrogen Monoxide NO NO2 N2O4 Dinitrogen Tetroxide N2O5

NIST Chemistry web-book

BCNOF

Week 2/Th: Ionic Cpd. Names

© DJMorrissey, 2o12

Ionic compounds – list the subunits present, start with positive ions (cations), end with negative ions (anions). The metals tend to be cations and there are relatively few elemental anions. Let’s try the same pattern:

FrF Francium Fluoride SnF2 Tin difluoride

Tin (II) fluoride Stannous fluoride

SnF4 Tin tetrafluoride Tin (IV) fluoride

Stannic fluoride

Week 2/Th: Ionic Cpd. Names

© DJMorrissey, 2o12

Ionic compounds – list the subunits present, start with positive ions (cations), end with negative ions (anions). The metals tend to be cations and there are relatively few elemental anions. Let’s try the same pattern:

FrF Francium Fluoride SnF2 Tin difluoride

Tin (II) fluoride Stannous fluoride

SnF4 Tin tetrafluoride Tin (IV) fluoride

Stannic fluoride

Week 2/Th: Polyatomic Ion Names

© DJMorrissey, 2o12

Cations: H3O+ hydronium NH4+ ammonium

Anions: NO2

- nitrite CO32- carbonate

NO3- nitrate HCO3

- hydrogen carbonate or bicarbonate SO3

2- sulfite HSO3

- hydrogen sulfite PO43- phosphate

or bisulfite HPO42- hydrogen phosphate

SO42- sulfate H2PO4

- dihydrogen phosphate HSO4

- hydrogen sulfate or bisulfate PLUS ABOUT 14 MORE

Polyatomic ions – the dreaded list of historical names ... Notice that most are anions and nearly all contain oxygen.

Week 2/Th: Ionic Cpds. with Polyatomic Ions

© DJMorrissey, 2o12

What is formula from name? Ammonium chloride NH4Cl Calcium hydroxide Ca(OH)2 What is formula for cpd. containing? Na+ and CO3

2- (sodium carbonate) Na2CO3 Al3+ and SO4

2- (aluminum sulfate) Al2(SO4)3 Mg2+ and PO4

3- (magnesium phosphate) Mg3(PO4)2

Ionic compounds – list the subunits present, start with positive ions, end with negative ions – must balance charge to make neutral compound

– generally do not use prefixes (mono-, di-, etc.)

Week 2/Th: More Polyatomic Ions

© DJMorrissey, 2o12

What is formula from name? Sodium acetate Na CH3CO2 Monosodium glutamate ?? (also known as MSG in foods) Na C5H8NO4 What is formula for cpds. found in pool cleaners? Lithium hypochlorite Li(ClO) or LiClO Calcium hypochlorite Ca(ClO)2 Copper (II) bromide CuBr2 Sodium bisulphate Na (HSO4) or NaHSO4