The following are the
(not the only!) asked topics on the regent’s exam from the Oxidation-Reduction and Electrochemistry Unit. Calculate oxidation numbers of elements in compounds and free elements. Identify Redox reactions. Identify oxidation or reduction half-reactions (free elements and their monatomic ions.) Identify oxidizing agents and substances oxidized in a chemical reaction. Identify reducing agents and substances reduced in a chemical reaction. An “electrochemical cell” is defined as either voltaic or electrolytic. Label an electrochemical cell (usually connected by a salt bridge) and tell the direction of electron flow and ion flow. Also label the cathode and anode. Writing half reactions(limited to free elements and their monatomic ions). Activity series using Table J.
You should know these facts about the Redox and Electrochemistry Unit. Redox reactions are the result of oxidation and reduction Losing electrons is oxidation (LEO) Gaining electrons is reduction (GER) The atom that loses electrons is called the reducing agent since it causes the other atom to gain electron The atom that gains electrons is the oxidizing agent since it causes the other atom to lose electrons Oxidation numbers (charges) indicate the gain or loss of electrons Positive oxidation numbers mean electrons were lost Negative oxidation numbers mean electrons were gained. The number of electrons gained must be equal to the number lost. Half reactions show the changes between the atoms that are oxidized and reduced In a chemical cell the electrons flow from one metal to another. Table J Reduction occurs at the cathode (becomes more negative) RED-CAT Oxidation occurs at the anode (becomes more positive) AN-OX (the red-cat had an-ox) Electrolysis/electroplating occurs with the help of an outside energy source Reference Tables to know for this section: Table J: Activity Series **, Reference Tables, pages 11-12. Review pages 8:1, 9:14-9:19. Review Book: Chapter 9, Sections A & B. Text Book: Chapters 20 & 21. dstreib: Regents Analysis – Redox and Electrochemistry
dstreib: Regents Analysis – Redox and Electrochemistry