The electrolysis of water

We'll go step by step through how to balance an oxidation reduction (redox) reaction in acidic solution. Most importantly, both charges and atoms must balance. Here are the steps: first, calculate oxidations numbers for all the elements in the equation. Next, figure out what is being oxidized and what is being reduced. Then, write half reactions for the oxidation and reduction. After that, balance each half reaction: first, for the atoms other than O and H, then for O and H, and finally for charge by adding electrons. After being balanced, the oxidation and reduction half reactions are ready to be added back to together. Make sure that the number of electrons is the same in the oxidation and reduction half reactions. If they are not, multiply one or both of the half reactions to make the number of electrons the same. Then, combine the oxidation and reduction half reaction, canceling out stuff that appears on both sides of the equation. Lastly, do a final check to make sure that everything balances: both atoms and charge.

In this video I look at the use of the two main reducing agents employed in organic chemistry. These are lithium aluminium hydride (lithal) and sodium borohydride. I outline the mechanism (nucleophilic addition) in which hydride ions react with C=O groups to form alcohols via alkoxide intermediates. I compare the reactivities of the two reducing agents and discuss the explosive risks associated with using lithium aluminium hydride with protic solvents such as water or methanol. A practical setup, that could be used to reduce aldehydes and ketone with lithal, is presented at the end. It is one in a series of short videos looking at the main organic practical techniques: heat & distill; reflux distillation; washing and drying in solvent extraction; recrystallisation and melting point determination; and others

Don't make the most common mistake in Oxidation Reduction! This question confuses so many students. Watch this video to learn how to do this right. In chemistry, reduction is the gain of electrons, and oxidation is the loss. Oxidation reduction reactions are often called redox reactions for short.

We'll learn how to determine the oxidation numbers or oxidation states for a the elements in a chemical compound. The oxidation numbers tell us how electrons are divided up or shared between atoms in a chemical compound. The oxidation numbers also tell us how electrons move in an oxidation reduction (redox) reaction. There are a set a rules that we use to determine oxidation number. Group 1A elements (alkalai metals) always have an oxidation of +1. Group 2A elements (alkaline earth metals) always have an oxidation number of +2. Elements on their own have an oxidation number of 0, and monatomic ions have an oxidation number that is equal to the ionic charge.

Electrolysis of copper sulfate and its use to refine blister copper by electrolytic refining.