week of february 28 - chem
week of february 28 - chem Chemistry 1030
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This 7 page Class Notes was uploaded by Emma Shoupe on Thursday March 3, 2016. The Class Notes belongs to Chemistry 1030 at Auburn University taught by Dr. Livia Streit in Spring 2016. Since its upload, it has received 30 views. For similar materials see General Chemistry 1 in Chemistry at Auburn University.
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Date Created: 03/03/16
GENERAL CHEMISTRY I –DR. LIVIA STREIT Week of February 28, 2016 March 1, 2016 Hydrates A compound that has a specific number of water molecules within its solid structure o Example copper(II) sulfate has 5 water molecules copper(II) sulfate pentahydrate CuSo4⋅5H 2 when water is driven off by heat, copper(II) sulfate becomes an anhydrous copper(II) sulfate with water = blue without water = white Molecular Mass the mass in atomic mass units of an individual molecule o multiply atomic mass for each element in the molecule by the number of atoms of that element then total masses average molecular weight = average amu on periodic table for ions o use empirical formula to find formula mass (formula weight) o same process as molecule Percent Composition a list of the percent by mass of each element in a compound empirical formula o mass in amu of one empirical formula Molar Mass mass in grams of 1 mole of substance o numerically equal to its atomic mass (element) compound- sum of molar masses of elements it contains 5.15 example in book Empirical Formula Percent Composition Step 1:Assume100gsothat %turns intograms Step 2:Convert tograms usingmolar mass todeter minethemoleratio Step 3:Divideeach molevalueby thesmallest valuetoget awhole number ratio *if thereis nowholenumber, multiply by thecommon fraction toget a wholenumber Togofrom an empirical formula toamolecular formula, themolecular weight has tobegiven. March 3, 2016 Chemical Bonding 6.1 Octet Rule atoms will lose, gain, or share electrons in order to achieve a noble gas electron configuration only 2 valence electrons contribute to bonding pairs of valence electrons not involved in bonding are lone pairs Lewis structure o Representation of covalent bonding o can be expressed with 2 dots or with a dash ( - ) Single bond o Sharing 1 pair of electrons between 2 atoms Double bond o Sharing 2 pairs of electrons between 2 atoms Triple bond o Sharing 3 pairs of electrons between 2 atoms Bond length o Distance between nuclei of 2 covalently bonded atoms o The stronger the bond, the shorter the bond o Triple bond is always shorter than double bonds o Double bond is always shorter than single bonds We quantify bond strength by measuring the quantity of energy required to break it 6.2 Electronegativity Covalent bonds occur between atoms that share electrons Ionic bonds occur between metal and nonmetal with ions Polar covalent bonds o Electrons shared but not shared equally Electrons “hang out” around the more electronegative element o A polar bond: Must have at least 1 polar bond (F, O, N, Cl) or… Must be asymmetrically shaped a lone pair on the central atom or… all bonding atoms are not the same Electronegativity o Ability of an atom in a compound to draw electrons to itself Varies with atomic numbers Nonpolar o Electronegativity differs by less than 0.5 Polar o Electronegativity differs by 0.5 – 2.0 Ionic o Electronegativity differs by 2.0 or more Dipole moment o Direction of electrons shift o Quantitative measure of polarity
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