Chemistry Unit 3
UNIT 5 – ELECTROCHEMISTRY
Chapter 9 – Electric Cells
9.1 – Oxidation and Reduction * The term reduction came to be associated with producing metals from their compounds.
* Ex. Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2
* Another substance, called a reducing agent causes or promotes the reduction of a metal compound to an elemental metal. In this example, it is CO.
* Corrosion, including the rusting of metals, is now understood to be similar to combustion.
* Reactions of substances with oxygen, whether they are combustion, burning, or corrosion, came to be called oxidation.
* Oxidation is a process in which metals are converted to compounds by most non-metals.
* This does not always occur with oxygen, as other gases such as Cl or Br are also used. * Ex. 2Mg(s) + O2(g) 2MgO(s) OR Cu(s) + Br2(g) CuBr2(s)
* A substance that causes the oxidation of metals to produce a metal compound is called an oxidizing agent. In this example, it is O2 and Br2.
Electron Transfer Theory * A redox reaction is a combination of 2 parts, each called a half-reaction.
* In Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)
* In the above reaction, the Zn(s) are converted to zinc ions in solution, Zn2+(aq).
* Therefore: Zn(s) Zn2+(aq) + 2e-
* Hydrogen ions in the solutions gain electrons and are converted to H2 gas. Thus becoming: 2H+(aq) + 2e- H2(g)
* According to modern theory, the gain of electrons is called reduction.
* According to modern theory, the loss of electrons is called oxidation.
* The total number of electrons gained in a reaction must equal the total # of electrons lost.
Oxidation States * Metals and monatomic anions tend to lose electrons (become oxidized), whereas non-metals and monatomic cations tend to gain electrons (become
Chapter 9 – Electric Cells
9.1 – Oxidation and Reduction * The term reduction came to be associated with producing metals from their compounds.
* Ex. Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2
* Another substance, called a reducing agent causes or promotes the reduction of a metal compound to an elemental metal. In this example, it is CO.
* Corrosion, including the rusting of metals, is now understood to be similar to combustion.
* Reactions of substances with oxygen, whether they are combustion, burning, or corrosion, came to be called oxidation.
* Oxidation is a process in which metals are converted to compounds by most non-metals.
* This does not always occur with oxygen, as other gases such as Cl or Br are also used. * Ex. 2Mg(s) + O2(g) 2MgO(s) OR Cu(s) + Br2(g) CuBr2(s)
* A substance that causes the oxidation of metals to produce a metal compound is called an oxidizing agent. In this example, it is O2 and Br2.
Electron Transfer Theory * A redox reaction is a combination of 2 parts, each called a half-reaction.
* In Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)
* In the above reaction, the Zn(s) are converted to zinc ions in solution, Zn2+(aq).
* Therefore: Zn(s) Zn2+(aq) + 2e-
* Hydrogen ions in the solutions gain electrons and are converted to H2 gas. Thus becoming: 2H+(aq) + 2e- H2(g)
* According to modern theory, the gain of electrons is called reduction.
* According to modern theory, the loss of electrons is called oxidation.
* The total number of electrons gained in a reaction must equal the total # of electrons lost.
Oxidation States * Metals and monatomic anions tend to lose electrons (become oxidized), whereas non-metals and monatomic cations tend to gain electrons (become