Unit 3: Atomic Theory & Masses - Michigan State University€¦ · Unit 3: Atomic Theory & Masses … -- nuclei, isotopes, nuclear mass -- elemental masses Unit 4: Molecules and Compounds
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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
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
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?
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 --
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!
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
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:
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:
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