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Department
Chemistry
Course
CHE 2A
Professor
A N D R E A S T O U P A D A K I S
Semester
Winter

Description
Study Guide Chem 2A Midterm 1 DISCLOSURE: I DO NOT OWN ANY OF THESE PICTURES NOR DO I TAKE CREDIT. C12 atom is 12 amu There is an infinite number of significant figures Cl35 (75.53mol) Cl37 (24.47mol) in 100 mol of chlorine there natural abundance NOT in 100 grams, atoms, molecules The carbon atomic mass shows us that: Stereochemical, structural, molecular, and empirical ALL can be used to obtain the % by mass composition of a chemical compound chemical species [16O=12O=13C=14C=17O]+2 Chemical species are atoms, molecules, molecular fragments, ions, etc., subjected to a chemical process or to a measurement. Nomenclature HF (hydrogen fluoride) CO (carbon monoxide) Why not carbon oxide? Because there are other molecular compounds of carbon and oxygen having atom ratio other than one C2H6O+ O2 > CO2+H2O Balance equation. 1C2H6O+ 2O2 > CO2+ 3H2O Formal Charge = #ve­ ­#e­ around element In the past you may have learnt that O is always ­2, however it is better to count each bond to an O as ­1 since there is a difference between C=O and C­O as seen by comparing the aldehyde and the alcohol in the diagram above. After all , the ­2 statement is wrong....e.g. in oxygen gas, O 2 the oxidation state is zero. If it is electronegative that it takes the electrons of the surrounding hydrogen. ex copper (II) sulfate pentahydrate = CuSO4­5H2O Calcium hydride = CaH2 Aluminum Oxide = Al2O3 Dinitrogen Monoxide = N2O B A(5)­­C D 5e(central atom) & 6 electrons how to find molecules? given variables .0050 grams of H2O want ozone (O3) molecules O3 molecules= .0050gH20 x 1mol/18.010gH2O 1mol O atoms/1 mol H2O x 1 mol O3/ 3 mol of O atoms x NA O3 molecules/ 1 mol O3 .0050x1x1x1xNA/ 18.016x1x3x1= 5.6X10E19 O3 molecules Molarity moles of solute/ Liters of solution how to find moles mass/ molar mass of solute compound (ex.H2O) Molecular compound has strong covalent bonds with a specific amount of atoms Ionic compounds are consisted of metals and nonmetals, and has formula units. ex. NaCl, Ca(OH)2 Covalent bonds happen between a nonmetal and a nonmetal. Metallic bonds occur between two metals. Oxidation number of C4H10O In elemental form (ex.Fe, S8), oxidation number is 0. Monatomic ions take their charge of monatomic ions. 1. The oxidation number for an atom in its elemental form is always zero. ○ A substance is elemental if both of the following are true: only one kind of atom is present ■ charge = 0 ○ Examples: ■ S 8 The oxidation number of S = 0 ■ Fe: The oxidation number of Fe = 0 2. The oxidation number of a monoatomic ion = charge of the monatomic ion. ○ Examples: ■ Oxidation number of S is -2. 3+ ■ Oxidation number of Al is +3. 3. The oxidation number of all Group 1A metals = +1 (unless elemental). 4. The oxidation number of all Group 2A metals = +2 (unless elemental). 5. Hydrogen (H) has two possible oxidation numbers: ○ +1 when bonded to a nonmetal ○ -1 when bonded to a metal 6. Oxygen (O) has two possilbe oxidation numbers: 2- ○ -1 in peroxides (2 )....pretty uncommon
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