CHM 101 1st EditionLecture 4 Last Lecture Overview- Molecular and Ionic compounds- Naming Compounds- Stoichiometry Lecture 4 OverviewI. Stoichiometry continued II. Balancing EquationsIII. Chemical ReactionsIV. Formula WeightContinuation of the last lecture- Chemical equations must be balanced so they obey the Law of Conservation of Mattero Matter is not created or destroyedo Atoms are not created or destroyed in chemical reactions- Coefficients give the ratio of substances in chemical reactionso Applied to the whole formula- Subscripts- number of individual atomsN2+ 3H2 2NH3 2 N atoms 2 N atoms6 H atoms 6 H atoms- Equations are balanced when the total number of each type of atom is the same on both sides- Often the states of reactants and products in chemical reactions are indicated o (g) gaso (l) liquido (s) solido (aq) aqueous solution 2Na (s) + 2H2O (l) 2NaOH (aq) +H2 (g)- Always remember to make sure the equation is balanced!3 simple Types of Chemical ReactionsI. Combination Reactions – 2 or more reactants combine to form a single producta. A + B ABII. Decomposition Reactions – single reactant breaks down to form two or more products a. AB A + BIII. Combustion Reactions – an organic compound is burned ( C, H, and sometimes O) in O to produce CO2 and H2Oa. CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (g)i. It’s easier to balance the O atoms last Formula Weight – sum of the atomic weights that make up a formula unit of an ionic compoundExample: MgCl21 Mg = 1 x 24.31 amu = 24.31 amu2 Cl = 2 x 35.45 amu = 70.90 amu 95.21 amuMolecular weight – sum of the atomic weights of all atoms that make up a molecule in a molecular compound (same as formula
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