Answer:
oxidation reaction.
Explanation:
Every reduction reaction must be accompanied by an oxidation reaction.
Oxidation leads electrons loss whereas reduction implies gain of electrons. So missing electrons should always be the equivalent of obtained electrons. Without something acquiring electrons there can't be any loss. Electrons can't simply disappear!
It implies, but, that oxidation and reduction must occur simultaneously at different locations and the electrons can commute across cables or in a liquid medium by ions.
To find out if a dye is a mixture or not, you can make use of the chromatography method of separation.
If the dye is a mixture, the different elements inside the mixture will be separated out during chromatography and they will form different bands on the cinematographic paper but if the dye is composed of only one element, only one band will be formed on the cinematographic paper.
I think the answer is reversible. Reversible reaction is a kind of reaction which can react in both direction at the same time. And when the both side reactions get the same speed, the reaction is at a equilibrium state.
I believe, that options 2. as well as 5. are the correct responses.
