Demo of the Week: Balancing Redox Reactions

Added: 2026-05-05

[00:00:00]Hi scientists. I'm Chikodi and I'm Andrew and  welcome back to another demo of the week.

[00:00:05][Demo of the Week: Balancing Redox Reaction Redox Reactions] Today we'll be talking about balancing redox reactions. But Chi, what is a redox reaction?

[00:00:11]Great question, Andrew. A redox reaction is a  type of chemical reaction categorized by the transfer of electrons. The compound that loses an  electron is called oxidized, and the compound that gains the electron is reduced. In today's demo,  we're going to be mixing potassium permaganate, which is purple, with sodium nitrite. We  expect the purple permaganate to disappear, turning into colorless manganese ions,  while the nitrite becomes nitrate.

[00:00:37][solid potassium permanganate is dissolved in water in left flask and solid sodium nitrite is dissolved in water in right flask] [the solutions are mixed together, generating a pink solution] But Andrew, our solution is still pink.  The solution is still currently pink because our reaction is incomplete.  Solution will stay pink instead of turning clear because our reaction is  right now unbalanced.

[00:01:05][MnO4- + NO2- --> Mn2+ + NO3-] Oh, I get it. Balancing a redox reaction  means that both mass and charge need to be balanced. Right now, our reaction here is  neither mass or charge balanced. But Andrew, why is being balanced on both sides of  the equation important? Great question, Chi. Being balanced on each side is  important because it shows us that nothing is created or destroyed in the reaction.  So, balancing makes sure that the electrons lost in oxidation are exactly equal to the  electrons gained in reduction. Oh, okay. So, it seems like for this equation, we need to  add additional protons to the solution to drive the reaction towards both being mass and charge  balanced. We'll do this by adding sulfuric acid.

[00:01:45][sulfuric acid is added to pink solution, generating a colorless solution] [5 NO3- + 2 MnO4- + 6H+ --> 2 Mn2+ + 5 NO3- + 3 H2O] This is our new solution as indicated  by our equation. We balanced this redox reaction by adding sulfuric acid,  adding some protons to the solution, and balancing the equation. All right, scientists, that's all we have for you today. We'll see you  next week for another demo of the week. Bye.