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jessica.so
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Q1: Why are titrations using permanganate performed in acid solution?
Q2: A bottle containing a standard solution of potassium permanganateis found to have brown stains on the inside. Why will this potassium permanganate be of no further use for quantitative experiments?
KNOWN:
Potassium Permanganate = KMnO4
It is known that potassium permanganate is a common lab oxidizing agent [it reduces]. It naturally has an intense purple color but when potassium permanganate is reduced all the way to Mn2+, it becomes colourless. A solution is titrated when a faint purple colour remains.
1/2 Reactions:
The reduction of permanganate:
In acid: MnO4- + 8H+ + 5e- ==> Mn2+ + 4H2O
In neutral solution: MnO4- + 4H+ + 3e- ==> Mn2+ + 2H2O
In base: MnO4- + e- ==> MnO42+
Q2: A bottle containing a standard solution of potassium permanganateis found to have brown stains on the inside. Why will this potassium permanganate be of no further use for quantitative experiments?
KNOWN:
Potassium Permanganate = KMnO4
It is known that potassium permanganate is a common lab oxidizing agent [it reduces]. It naturally has an intense purple color but when potassium permanganate is reduced all the way to Mn2+, it becomes colourless. A solution is titrated when a faint purple colour remains.
1/2 Reactions:
The reduction of permanganate:
In acid: MnO4- + 8H+ + 5e- ==> Mn2+ + 4H2O
In neutral solution: MnO4- + 4H+ + 3e- ==> Mn2+ + 2H2O
In base: MnO4- + e- ==> MnO42+