13 – Standardising a Sodium Thiosulfate Solution (LC 2027) (Leaving Cert Chemistry): Flashcards
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14 cards from this deck
Standardisation definition
Standardisation definition
Finding exact conc. by titrating vs known standard solution
Aim of standardisation
Aim of standardisation
Determine exact conc. via iodine-thiosulfate titration
Products of + reaction
Products of + reaction
, ,
+ products
+ products
+
Purpose of white tile
Purpose of white tile
Observe colour changes clearly
Why add to flask
Why add to flask
Make solution acidic for permanganate reaction
Why excess KI used
Why excess KI used
Ensure complete reduction of permanganate ions
Initial solution colour (before KI)
Initial solution colour (before KI)
Purple (from )
Colour after KI addition
Colour after KI addition
Reddish-brown (from formed)
When to add starch indicator
When to add starch indicator
When solution becomes pale yellow
Colour immediately after starch added
Colour immediately after starch added
Blue-black (starch-iodine complex)
End point colour in this titration
End point colour in this titration
Colourless (blue-black disappears completely)
Why add starch when pale yellow, not early
Why add starch when pale yellow, not early
Starch- complex more stable at low conc.
What end point indicates
What end point indicates
All iodine has reacted with thiosulfate
