CHAPTER 5 Review General, Organic, & Biological Chemistry Janice Gorzynski Smith
Concepts to Know 2 Smith. General Organic & Biolocial Chemistry 2nd Ed. Define a chemical reaction Correctly write a chemical reaction Balance reactions by inspection Calculate molecular mass for any compound or molecule Apply mole ratios within molecules and between molecules. Solve stoichiometry problems Convert between mass and moles Convert between % composition and mass Identify limiting reagent Calculate percent yield Identify reduction and oxidation equations and pick out the compound being reduced or oxidized
Need to Memorize 3 Smith. General Organic & Biolocial Chemistry 2nd Ed x is Avogadro’s number. Oxidation is the loss of electrons from an atom. Reducing agents are reduced Reduction is the gain of electrons by an atom. Oxidizing agents are reduced.
4 Smith. General Organic & Biolocial Chemistry 2nd Ed. aA ( physical state ) + bB ( state ) cC ( state ) + dD ( state ) Writing and Balancing Equations HOW TO Balance a Chemical Equation Step [1] Write the equation with the correct formulas. The subscripts in a formula can never be changed to balance an equation, because changing a subscript changes the identity of a compound. Step [2] Balance the equation with coefficients one element at a time. Step [3] Check to make sure that the smallest set of whole numbers is used.
5 aA + bB cC + dD mass Amass Bmass Cmass D moles Amoles Bmoles Cmoles D a:b b:c c:d a:c a:d x ÷ MM Solve Stoichiometry Problems Limiting Reactant: Compare moles A & moles B after applying mole ratio. The reactant with the least number of moles AFTER mole ratio considered is the limiting reactant. Use limiting reactant # moles to determine moles of products that form
6 Smith. General Organic & Biolocial Chemistry 2nd Ed. Zn + Cu 2+ Zn 2+ + Cu Zn loses 2 e – Cu 2+ gains 2 e − 6 Oxidation half reaction:ZnZn e − Each of these processes can be written as an individual half reaction: loss of e − Reduction half reaction:Cu e − Cu gain of e − Redox Half Reactions