Chemistry (reaction)

a) The first one is acidic and the second one is alkaline (so simple-_-)

b) In can be made from MnO2 in industry.

2 MnO2 + 4 KOH + O2 → 2 K2MnO4 + 2 H2O
2 MnO42– + Cl2 → 2 MnO4– + 2 Cl–

or:

3 K2MnO4 + 2 CO2 → 2 KMnO4 + 2 K2CO3 + MnO2

(This is not required in HKDSE in all likelihood (90%)

c)In the reaction of alkene and alkaline potassium permanganate, "diol" will be
produced instead. Alkene gain both hydrogen and oxygen!!!

c+d) In theory, redox reaction refers to change in oxidation number instead.
The adding or removal of oxygen is only the BASIC definition introduced in the
beginning of redox reaction. (You must clear your misconception!!!) If you explain
redox reaction in terms of gain or loss of oxygen instead of change in oxidation
number, you will receive NO marks in your exam!!

e) Alkene will reacts with KMnO4 to form "diol, which then converted into
carboxylic acids directly without converting into aldehydes first. Therefore NO
carbonyl compounds will be formed since it is strong oxidizing agent. If KMnO4
used is too strong, side products may form.

2013-07-26 09:59:12 補充：
3) It is because MnO4- is reduced to form Mn2+ while alkene gains oxygen to form diol.

5) When it involves in change in oxygen, it is redox reaction. BUT when it does not involve
in change in oxygen, we will look at the change in oxidation number to determine whether
it is redox reaction or not.

2013-07-26 10:15:47 補充：
The reaction that involves change in oxygen must also involve
in change in oxidation number. So that's why we use oxidation number as an explanation
instead of gain or loss in oxygen.

For 3) I must correct my mistake that MnO4- is reduced to MnO2 since it is alkaline
KMnO4