CHEM 210 1st Edition Lecture 16Outline of Last Lecture I. PrecipitatesII. Soluble Ionic CompoundsIII. Insoluble Ionic CompoundsIV. Strong/Weak Acids and BasesOutline of Current Lecture V. Oxidation and ReductionCurrent LectureOxidation occurs when the oxidation number of a reactant is increased in the product. Reduction however, is the opposite and occurs when the oxidation number is less in the productthan in the reactant. There are a set of rules used to find oxidation numbers in compounds.- When an atom is in its elemental form, the oxidation number is always 0.- Oxidation numbers of monoatomic numbers are the charges of the ion.Ex. Al3+ = +3- Oxidation numbers of group 1A elements from the periodic table are always +1, unless they are elemental.- Oxidation numbers in group 2A are always +2, unless they are elemental.- Hydrogen and Oxygen have two oxidation numbers.Hydrogen = -1 when bonded to a metal and +1 when bonded to a nonmetalOxygen = -2 in all compounds but -1 if it is a peroxide.- The oxidation number of Fluorine is always -1The net charge, or the sum of all the oxidation numbers in a neutral compound is 0.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.The sum of all oxidation numbers of all atoms in a polyatomic = the charge of the ion.Examples:1. Find the oxidation numbers of zinc and chlorine in zinc chloride (ZnCl2)We first look to see that chlorine has an oxidation number of -1. There are two of them, which gives it an overall number of -2. To balance out the -2, zinc must have am oxidation number of +2. 2. Find the oxidation number of chromium in (Na2CrO4)We first look at our rules and see that sodium (Na) has an oxidation number of +2. We also know that oxygen has an oxidation number of -2, but since there are 4, we multiply to get -8. (-2 x 4). Now we set that equal to 0 which is the net charge of the neutral compound and solve for chromium. (+2)+(?)+ (-8) = +6 Losing electrons results in oxidation, while gaining electrons results in reduction. When electrons are lost, the oxidation number goes up, whereas when electrons are gained, the oxidation number goes down. One which oxidizes itself is the reducing agent, while one which reduces itself is the oxidizing agent. They are
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