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Chapter #7 Chemical Formulas and Chemical Compounds NearingZero.net. Section 1 Chemical Names and Formulas. Chemical Formulas C 6 H 12 O 6 Al 2 (SO 4 ) 3. Subscript indicates that there are 6 carbon atoms. Positive Ions Write the name of the element Write the word ion
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Chapter #7 Chemical Formulas and Chemical Compounds NearingZero.net
Section 1Chemical Names and Formulas • Chemical Formulas • C6H12O6 Al2(SO4)3 Subscript indicates that there are 6 carbon atoms
Positive Ions Write the name of the element Write the word ion Na+ = Sodiumion Transition elements use Roman Numerals Fe +2 = Iron(II)ion Negative Ions Write the name of the element Change the ending to –ide Write the word ion Cl- = Chlorideion Monatomic Ions
Binary Ionic Compounds • 2 elements= Binary • Metal + nonmetal = ionic • Write the name of the 1st element • Write the name of the 2nd element • Change the ending to –ide • NaCl =Sodium Chloride • MgCl2 =MagnesiumChloride
Stock System • Uses roman numerals • Write the name of the 1st element • Write the oxidation number of the 1st element • Write the name of the 2nd element • Change the ending to –ide • CrF3 =Chromium(III)Flouride • NiF
Binary Molecular Compounds • Molecular= covalent PG 212 Prefixes • Write the name of the 1st element • Write the name of the 2nd element • Change the ending to –ide • Put in prefixes • Only use prefixes on the 1stelement if it is more than 1 NO2= Nitrogen Dioxide N2O3
Binary Acids • Acids always begin with H • Acids that consist of 2 elements • Write hydro • Write the 2nd element • Change the ending to –ic • Write the word ACID • HF= Hydrofluoric Acid • HBr
Oxyacids • Are acids that contain hydrogen, oxygen, and a third element. • Never use Hydro • Write the name of the polyatomic(pg 210) • Change the ending to –ic or –ous (ate -ic & ite –ous) • Write the word ACID • H2SO4 = sulfuric acid • H3PO4
Polyatomic Compounds • Write the name of the 1st element • Write the name of the polyatomic (pg 210) • NaNO3 = SodiumNitrate • AgNO2
Section 2 Oxidation Numbers • Oxidation numbers- are assigned to the atoms in molecules, including molecular ions, to show the general distributions of electrons among the bonded atoms. +1 +/- 4 +2 +3 -3 -2 -1
Oxidation numbers • Rules pg 216 • UF6 • UF6 criss cross the numbers up • Check the 2nd element using the periodic table • U= +6 F= -1 • Polyatomic compounds do a math line +3-8 =0 H= +1 P= 5 O=-2 +1-2 H3PO4 • If there is an ION (charge) do a math line
Practice oxidation numbers • GeCl2 • CS2 • ClO3- • H2SO4 • PCl3 • HNO3 • GeO • SO4-2 • NO2-
Section 3 Using Chemical Formulas • Formula mass (molar mass or weight) of any compound or polyatomic ion is the sum of the average atomic masses of all the atoms represented in the formula. • H20 H x 2= 2.014g O x 1 = 15.999g 18.013 g of H2O
Old stuff • Mole to grams • Grams to moles • Moles to particles • Particles to moles • Grams to particles • Particles to grams
Percent Composition % comp= Mass of element in the sample mass of sample (formula mass) Calculate the % comp of H2O X 100
Section 4 Determining Chemical Formulas • Empirical Formula- (simplest formula) consists of the symbols for the elements combined in a compound, with subscripts showing the smallest whole-number mole ratio of the different atoms in the compound. • C2H6 simplest formula would be CH3
Empirical Formulas • Drop the % signs and add grams • Covert to moles of each element • Take the smallest number of moles and divide it into all the other values • Write the formula Determine the empirical formula for a sample that contains 78.1% B & 21.9% H
Molecular Formulas • Do the same 4 steps for determining empirical formulas • Add up the formula mass of the empirical formula • Use the molecular formula mass in the question • Use the formula X= Molecular formula mass empirical formula mass • Use the x and multiply your empirical formula using it
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