14.8 redox titrations Flashcards
1
Q
what is the colour change using maganate ions?
A
colourless -> pink/purple
2
Q
which acid is needed to acidify MnO4-? why?
A
H2SO4; supply 8H+
3
Q
why can’t conc. HCl be used instead in reducing MnO4-?
A
Cl- is oxidised to Cl2
- greater volume of MnO4- used
- poisonous Cl2 gas produced
4
Q
why can’t HNO3 be used in reducing MnO4-?
A
it is a oxidising agent; Ecell of NO3- to HNO2 is larger than Fe3+ to Fe2+
-> smaller volume of manganate used
5
Q
how does weak acids / insufficient amount of acids affect the accuracy of manganate redox?
A
insufficient acid / weak acid produces MnO2 instead (brown)
-> masks colour change leads to greater volume used
