Redox Reactions

[JamieLeaf]

Hey Guys,
For redox reactions, will they tell you if a redox reaction is occurring under basic or acidic solution or do you need to determine this by yourself and if so how do you do this? Thanks!!

[Srd2000]

Hey hey, you'll either be told that it's acidic or alkaline (basic), or you have to look at the half-equations present.

Have a look at the 2017 VCAA Chem Exam on question 6 of the extended response. The important information we're given to determine if it is acidic or alkaline is the diagram of the PEM (proton exchange membrane) and chemicals involved. Knowing them and using the electrochemical series we'll get the relevant half-equations. If the hydrogen equation has H⁺, it's acidic. If the hydrogen equation has OH^-, it's basic. Doing that for this question we have H₂ --> 2H⁺ + 4e^- and O₂ + 4H⁺ + 4e^- --> 2H₂O. Obviously we have H⁺, meaning we have an acidic environment. Yippie!

Take a look at the 2018 VCAA Chem Exam on question 8 of the extended response again. This time we're told it is alkaline (basic), so that's easy.
But if it didn't and instead had some species like Ni(OH)₂ or Al(OH)₃ for example we could determine that it is basic by the presence of the OH^- groups. Does this make sense?

Long story short, you should be able to figure out if it acidic or basic pretty easily once you know. Let me know if something doesn't make sense or anything. Good luck!