Week 2/Th: Lecture Unit 4 Symbols

Transcription

1 Week 2/Th: Lecture Unit 4 Symbols 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 08:00AM

2 Issues, Textbook Error Lower case English m stands for milli and 10 3 Lower case Greek µ stands for micro and 10 6 Gasoline in Windsor, Canada is selling for CA$ / L, what is this in US$ / Gal? Facts: 1 Gal = L, 1 US$ = CA$ = CA$/L * 1 US$/ CA$ * L/Gal = US$ / Gal = US$ / Gal (proper sigfig)

3 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 g before and only g after popping. 1) What percentage of its mass was lost during popping? = [mass lost / total mass ] *100 = [ ( ) g / g ] *100 = [0.019/0.125]*100 = 15 % (proper sigfig) 1) How many kernels are in a 1.00 pound bag of popcorn? = 1.00 lb * g/lb *1 kernel/0.125 g = kernels = 3.63x10 3 kernels (proper sigfig)

4 Week 2/Th: Chemical Compounds 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

5 Week 2/Th: Compound Type & Nomenclature 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!

6 Week 2/Th: Systematic Names Molecular compounds list the elements present, start with most reactive metals, end with most reactive nonmetals. Use Greek prefixes for indicating the amount of each element Mono Neutral combinations of N with O Di N Tri 2 O Dinitrogen Monoxide NO Tetra NO Penta 2 N Hexa 2 O 4 Dinitrogen Tetroxide N 2 O 5 BCNOF NIST Chemistry webbook CCl 4 Carbon tetrachloride CO Carbon Monoxide CO 2 Carbon Dioxide

7 Week 2/Th: Ionic Cpd. Names 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 SnF 2 Tin difluoride Tin (II) fluoride Stannous fluoride SnF 4 Tin tetrafluoride Tin (IV) fluoride Stannic fluoride

8 Week 2/Th: Ionic Cpd. Names 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

9 Week 2/Th: Polyatomic Ion Names Polyatomic ions the dreaded list of historical names... Notice that most are anions and nearly all contain oxygen. Cations: H 3 O + hydronium NH 4 + ammonium Anions: NO 2 nitrite CO 2 3 carbonate NO 3 nitrate HCO 3 hydrogen carbonate or bicarbonate SO 2 3 sulfite HSO 3 hydrogen sulfite or bisulfite PO 3 4 phosphate HPO 2 4 hydrogen phosphate SO 2 4 sulfate H 2 PO 4 dihydrogen phosphate HSO 4 hydrogen sulfate or bisulfate PLUS ABOUT 14 MORE

10 Week 2/Th: Ionic Cpds. with Polyatomic Ions 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.) What is formula from name? Ammonium chloride NH 4 Cl Calcium hydroxide Ca(OH) 2 What is formula for cpd. containing? Na + and CO 3 2 (sodium carbonate) Na 2 CO 3 Al 3+ and SO 4 2 (aluminum sulfate) Al 2 (SO 4 ) 3 Mg 2+ and PO 4 3 (magnesium phosphate) Mg 3 (PO 4 ) 2

11 Week 2/Th: More Polyatomic Ions What is formula from name? Sodium acetate Na CH 3 CO 2 Monosodium glutamate?? (also known as MSG in foods) Na C 5 H 8 NO 4 What is formula for cpds. found in pool cleaners? Lithium hypochlorite Li(ClO) or LiClO Calcium hypochlorite Ca(ClO) 2 Copper (II) bromide CuBr 2 Sodium bisulphate Na (HSO 4 ) or NaHSO 4