For the oxidation-reduction reaction equation given here,
2Li+Se -> Li2Se
Indicate how many electrons are transferred in the formation of one formula unit of product?
Concepts and reason
In a balanced oxidation-reduction reaction, the number of electrons lost by reductant is equal to the number of electrons gained by the oxidant.
Fundamentals
The reduction is the process in which a species gains electrons and increase in negative charge and the oxidation is the process in which the species loses electrons and increases the positive charge.
The species which undergoes reduction is called as oxidant and the species which undergoes oxidation is called as reductant.
Answer:
The given reaction is as follows:
The oxidation half-reaction is as follows:
The reduction half-reaction is as follows:
Explanation:
In this reaction, Li undergoes oxidation by losing one electron and Se undergoes reduction by gaining 2 electrons.
Balance the electrons in the two half-reactions and add as follows:
Therefore, the number of electrons transferred in the formation one formula unit of product 
is 2.
Explanation:
The electrons in the two half-reactions are balanced by the multiplying the oxidation half-reaction with 2. Hence, 2 electrons are transferred in the formation of one formula unit of product.