Standardising a KMnO4 Solution(Complete) Flashcards
What is different about KMnO4 when reading the meniscus?
You read from the top of the meniscus at eye level.
What is a standard solution?
One whose concentration is known accurately.
What is the standard solution used in standardising a KMnO4 solution?
Ammonium iron II sulphate solution.
What indicator is used in this titration and why?
Standardising a KMnO4 solution
No indicator.
KMnO4 acts as its own indicator.
When is the first lot of sulphuric acid added and why?
When making up the Ammonium iron II sulphate solution.
To prevent atmospheric oxygen from oxidising Fe2+ to Fe3+.
When is the second lot of sulphuric acid added and why?
It is put into the conical flask immediately before titration.
To ensure the reaction goes to completion- to ensure the complete reduction of MnO4- to Mn2+.
To prevent the formation of a brown precipitate of MnO2.
What happens if not enough H2SO4 is added?
A brown precipitate of MnO2 forms.
How is the end-point of the titration of standardising a KMnO4 solution determined?
When the solution becomes a permanent pink.
What is autocatalysis?
Where a product of a reaction, Mn2+ catalyses the reaction.
