Oxidation-Reduction Reactions - Chemistry Post-lab Discussion PDF

PRAYER BEFORE CLASS Holy Spirit, Divine Creator, true source of light and fountain of wisdom! Pour forth your brilliance upon my dense intellect, dissipate the darkness which covers me, that of sin and of ignorance. Grant me a penetrating mind to understand, a retentive memory, method and ease of le...

PRAYER BEFORE CLASS Holy Spirit, Divine Creator, true source of light and fountain of wisdom! Pour forth your brilliance upon my dense intellect, dissipate the darkness which covers me, that of sin and of ignorance. Grant me a penetrating mind to understand, a retentive memory, method and ease of learning, the lucidity to comprehend, and abundant grace in expressing myself. Guide the beginning of my work, direct its progress and bring it to successful completion. This I ask through Jesus Christ, true God, and true man, living and reigning with You and the Father, forever and ever. Amen.  UST General Santos Post-laboratory Discussion: Reduction-Oxidation Reactions Chemistry for Engineers Laboratory LEARNING OBJECTIVES at the end of the experiment, students are expected to: ❖ Define and differentiate between oxidation and reduction reactions. OUTLINE Reduction-Oxidation Reactions Electrochemistry ○ Galvanic Cell ○ Electrolytic Cell  UST General Santos I.Reduction- Oxidation Reaction WHAT IS REDOX REACTION? - are chemical reactions involving oxidation and reduction occurring simultaneously Redox reactions cover a wide range of reactions and they can be explained in terms of: loss or gain of oxygen loss of gain of hydrogen transfer of electrons changes in oxidation number the word “redox” come from reduction and oxidation REDOX REACTION - ELECTRONS - An increase in the oxidation number means loss of electrons and oxidation has occurred - a decrease in the oxidation number means electrons have been gained and reduction has occurred OXIDATION - first used to describe reactions in which oxygen combined with an element or compound to form another substance - a substance is oxidised if it gains oxygen, loses hydrogen, loses electrons, and increases its oxidation state after a reaction REDUCTION - in the beginning, referred as the removal of oxygen from an oxygen-containing compound - substance loses oxygen, gains hydrogen, gains electrons or decreases its oxidation state after a reaction DIFFERENCE BETWEEN OXIDATION AND REDUCTION REDOX REACTION - The substance in the reaction that gives up electrons is referred as reducing agent - The substance in the reaction that takes up electrons is called oxidizing agent  UST General Santos II. Electrochemistry: Fruit Battery and Electroplating ELECTROCHEMISTRY - field of chemistry involving the study of transformation of chemical energy to electrical energy and vice versa - reactions that occur are redox reactions - occur through the use of an electrochemical cell ELECTROCHEMICAL CELL - a device used to convert the chemical energy produced in a redox reaction into electrical energy and vice versa - two types: - galvanic cell - electrolytic cell ELECTROCHEMICAL CELL all electrochemical cells have several common features - have two electrodes (anode and cathode) - electrodes are dipped into an electrolyte (solution that contains a mixture of ions and will conduct electricity) - in redox reactions, electrons are transferred from the oxidized substance to the reduced substance ELECTROCHEMICAL CELL ELECTROCHEMICAL CELL: Galvanic Cell device in which electrons from reaction transfer through an external path or circuit - uses a spontaneous redox reaction to generate electrical energy cathode (+): electrode where reduction occurs anode (-): electrode where oxidation occurs RED CAT: REDuction at the CAThode GALVANIC CELL circuit between half-cells is connected by a salt bridge (contains an electrolyte solution) flow of electrons is from the anode to cathode through a connecting wire driving force of the flow of electrons is in the form potential difference (electrode potential, E) RED CAT: REDuction at the CAThode ELECTROLYTIC CELL electrical energy is used to force a nonspontaneous chemical reaction to occur commonly used to electroplate metals, recharge batteries and split compounds into useful gases electrolytic cell is hooked up to a battery or power supply so the flow of electrons is pushed by an outside force cathode of the electrolytic cell is connected to the anode of the battery and therefore is negative anode of the electrolytic cell is connected to the cathode of the battery and therefore is positive GALVANIC VS ELECTROLYTIC CELL ELECTROPLATING - coating the metal of one electrode with the metal of the other - uses a form of electrolysis in which electrodes play a bigger role than just conducting - process of placing one metal over another RUST AND CORROSION - corrosion is a galvanic process by which metals deteriorate through oxidation - corrosion can be viewed as the process of returning metals to their natural state (ore) - metal is oxidized causing the loss of structural RUST AND CORROSION  HOW TO PREVENT CORROSION? BARRIER COATING easiest and cheapest way uses barrier coatings such as paint or plastic paints act as coating to protect the metal surface from the electrochemical charge that comes from corrosive compound - paint layers: primer coat (inhibitor), intermediate coat (adds to thickness, finish coat (resistance to HOW TO PREVENT CORROSION? ELECTROPLATING - most popular - electrodeposition of a metal onto the surface of a steel or iron product - common: zinc HOW TO PREVENT CORROSION? CATHODIC PROTECTION use of a more easily oxidized metal to protect iron for corrosion active sites on the metal surface are converted to passive site more reactive metal becomes the anode and iron becomes the cathode - metals used for anodes include aluminum, magnesium or zinc OXIDATION REACTIONS ADVANCED OXIDATION PROCESS - wastewater treatment processes at near ambient temperature and pressure that produce a very active radicals for degradation of pollutants - active radicals: hydroxyl radical, superoxide radical anions, sulfate radicals - oxidation process breaks down complex molecules into simpler, less harmful substances  UST General Santos Post-laboratory Discussion: Oxidation-Reduction Reactions Chemistry for Engineers Laboratory PRAYER AFTER CLASS Grant me, O Lord my God, a mind to know you, a heart to seek you, wisdom to find you, conduct pleasing to you, faithful perseverance in waiting for you, and a hope of finally embracing you, Amen.