Redox Titrations

Question 1

What ions are used in a titration to determine Iron (2) ions

Answer 1

Manganate (7) ions- MnO4 2-
Titration of manganate + Iron

Question 2

What are the steps involved in titration of manganate + Iron

Answer 2

1- Iron solution acidified with sulphuric acid
2- KmnO4 (potassium manganate) added from burette
3- solution is colourless until end point = pink

Question 3

Why does the solution go colourless at the end point of the iron + manganate titration

Answer 3

Kmno4 goes colourless when reduced = colour change shows all reducing agent (Fe2+) ions have reacted

-potassium manganate is usually pink so when the solution goes pink it means there are no longer any more Fe2+ ions to react with/reduce them

Question 4

What ions are used to determine concentration of Iodine in titration

Answer 4

Thiosulfate ions
S2O3

Question 5

Give the steps involved in the titration of Iodine

Answer 5

First = Pottasium Iodide + oxidising agent = produce Iodine

1- Iodine solution out in flask
2- Thiosulfate ions added from burette
3- Solution brown = to pale yellow at end point
4- Starch indicator added
5- Blue to Colourless at end point = shows all iodine has turned to Iodide ions

Question 6

What is the use of the Iodine + Thiosulfate titration

Answer 6

Used to investigate the strength of the original oxidising agent used to produce Iodine

• the more powerful oxiding agent will produce more Iodine = more thiosulfate needed to fully reduce iodine back to iodide ions

Question 7

Why is sulfuric acid added in the titration between iron + manganate

Answer 7

Provides H+ ions for redox reaction
Helps prevent oxidation of Fe2+ to Fe3+ in aid before experiment

Question 8

Why can HCl not be used instead of sulphuric acid in iron + managanate titration

Answer 8

HCl reacts with / is oxidised by Manganate (7) MnO4- ions = forms chlorine gas