IB SL Chemistry Unit 9 | Kentucky State University

University:
Kentucky State University
Course:
CHE 101 | General Chemistry I
Academic year:

2023
Views:

308

Pages:

4
Author:

Payton Perry

UNIT NINE ● Redox Reactions ○ Oxidation can be defined as the loss of hydrogen or gain of oxygen. ○ Reduction is gain of hydrogen or loss of oxygen. ○ The oxidising agent becomes reduced, while the reducing agent becomes Oxidized. ● Oxidation Reactions can be split into two half reactions. ○ One species is oxidized ○ One is reduced ○ In this case, our two half reactions would be ○ Zn→Zn2+ and Cu2+→Cu ● Balancing Redox reactions ○ First write out two half reactions ○ Then balance for molecules on each side ○ Then balance for oxygens first by adding water molecules ○ Balance for hydrogen atoms by adding hydrogen ions ○ Balance each oxidation and reduction by adding electrons ○ Make both reactions have same amount of electrons on same side then cancel the electrons out ● Winkler Method - Must know ○ Solves for Biological Oxygen Demand (BOD) ○ BOD is amount of oxygen needed to decompose organic matter in an ecosystem ○ Steps ■ Step one ● Saturate the water with oxygen ■ Step 2 ● Let it sit over a few days for bacteria to oxidise the organic material in there ■ Step 3 ● Fix the sample by adding ManganeseSulfate ● Manganese sulfate should be oxidized into manganese oxide ■ Step 4 ● Acidify the solution then add excess iodide to the solution. ■ Step 5. ● Titrate the iodide solution with sodium thiosulfate ○ To find BOD ■ Take the final concentration of oxygen, subtract the initial. ● Galvanic Cells, also known as voltaic cells ● Contents ○ Contains a salt bridge for ions to flow ○ A cathode with a copper rod that is reduced, and an anode with an oxidized species of zinc. Ions flow from anode to cathode. ● Cell Diagram Convention ○ Quick way to represent galvanic cell ● Electrolytic Cells ○ Breakdown of compound into its constituent elements ○ Oxidation happens at positive anode ○ Reduction at negative cathode ○ Uses a molten liquid in place of a salt bridge ○ endothermic reaction that’s non-spontaneous ○ Converts electrical energy into cell energy.