Corrosion and Redox Reactions Quiz

Prayer Before Class

• Holy Spirit, the true source of wisdom and light, dispel darkness and ignorance.
• Grant a penetrating mind, a strong memory, and ease in learning.
• Guide the work, direct progress, and bring it to success.
• Ask through Jesus Christ, true God and man, for blessings, and His continued reign.
• Pray for God's grace and strength.

Post-Laboratory Discussion: Reduction-Oxidation Reactions

• This discussion is about Reduction-Oxidation Reactions in Chemistry for Engineers Laboratory at UST General Santos.

Learning Objectives

• Define and differentiate between oxidation and reduction reactions.

Outline

• Reduction-Oxidation Reactions
  • Electrochemistry
    • Galvanic Cell
    • Electrolytic Cell

Reduction-Oxidation Reaction

• A broad range of reactions involving simultaneous oxidation and reduction.

What is Redox Reaction?

• Chemical reactions involving simultaneous oxidation and reduction.
• Explained in terms of:
  • Loss or gain of oxygen
  • Loss or gain of hydrogen
  • Transfer of electrons
  • Changes in oxidation number

Redox Reaction - Electrons

• Increase in oxidation number = loss of electrons, oxidation has occurred.
• Decrease in oxidation number = gain of electrons, reduction has occurred.

Oxidation

• Originally described as combining oxygen with an element to form a new substance.
• A substance is oxidized if it gains oxygen, loses hydrogen, loses electrons, and increases its oxidation state after a reaction.

Reduction

• Initially described as removing oxygen from an oxygen-containing compound.
• A substance loses oxygen, gains hydrogen, gains electrons, and decreases its oxidation state after a reaction.

Difference Between Oxidation and Reduction

• Oxidation: gain of oxygen, loss of hydrogen, loss of electrons, increase in oxidation number.
• Reduction: loss of oxygen, gain of hydrogen, gain of electrons, decrease in oxidation number.

Redox Reaction

• Reducing agent: gives up electrons.
• Oxidizing agent: takes up electrons.
• Example: Zn + S → ZnS (Zn is the reducing agent, S is the oxidizing agent.)

Electrochemistry: Fruit Battery and Electroplating

• Study of transformations between chemical and electrical energy.
• Redox reactions occur through electrochemical cells.

Electrochemistry

• Field of chemistry involving studying the transformation of chemical energy to electrical energy.
• Reactions occurring are redox reactions.
• Occur through the use of electrochemical cells.

Electrochemical Cell

• Device for converting chemical energy in redox reactions into electrical energy and vice versa.
• Two types:
  • Galvanic cell
  • Electrolytic cell

Electrochemical Cell (continued)

• All electrochemical cells share common features:
  • Two electrodes (anode and cathode)
  • Electrodes submerged in an electrolyte (conductive solution)
  • Electron transfer between oxidized and reduced substances.

Electrochemical Cell (continued)

• Cathode: positive terminal, reduction takes place, electrons move into the cathode.
• Anode: negative terminal, oxidation takes place, electrons move out of the anode.

Electrochemical Cell: Galvanic Cell

• Devices transferring electrons from reaction transfer through an external circuit.
• Uses a spontaneous redox reaction to generate electrical energy.
• Cathode (+): where reduction occurs.
• Anode (-): where oxidation occurs.

Galvanic Cell

• Circuit between half-cells connected by a salt bridge.
• Electrons flow from anode to cathode through a connecting wire.
• Driving force of electron flow = electrode potential (E).

Electrolytic Cell

• Using electrical energy to force a nonspontaneous chemical reaction to occur.
• Hooked up to a battery or power supply.
• Cathode is (-) and connected to the anode of the battery.
• Anode is (+) and connected to the cathode of the battery.

Galvanic vs. Electrolytic Cell

• Galvanic: spontaneous redox reactions generates electricity.
• Electrolytic: non-spontaneous reactions use electricity

Electroplating

• Coating one electrode with another metal.
• Electrolysis where electrodes play a major role in placing one metal over another.

Rust and Corrosion

• Galvanic process where metals deteriorate due to oxidation.
• Corrosion is the process of returning metal to its natural ore state.
• Metal oxidized, losing structural integrity.

Rust and Corrosion (continued)

• Iron hydroxide forms & is quickly oxidized.
• Cathode action reduces oxygen and forms hydroxide ions.
• Anode action causes pitting of the iron.

How to Prevent Corrosion

• Barrier Coating: uses coatings like paint or plastics to prevent electrochemical charge.
• Electroplating: electrodeposition of a metal on a steel or iron surface (zinc is common)
• Cathodic protection: use of a more reactive metal than iron to protect it from oxidation.

Oxidation Reactions

• Advanced oxidation processes (AOPs) involve wastewater treatment to produce active radicals that degrade pollutants.
• AOPs break down complex pollutants into simpler, less harmful substances.

Prayer After Class

• Grant a mind to know God, a heart to seek wisdom, and a conduct pleasing to God.
• Express faithful perseverance in waiting for and finally embracing God.

Test your knowledge on the roles of barrier coatings, cathodic protection, and redox reactions in preventing corrosion and chemical changes. This quiz covers essential concepts regarding oxidation, reduction, and the materials used in these processes. Perfect for students studying chemistry or environmental science.