You should never touch the subscripts, as that will change the composition. Hope I helped!
Answer:
Oxidation or Exothermic reaction
Explanation:
Oxidation means gain of oxygen.
Exothermic means loss of heat to combine 2 elements
A change will only occur one time in unidirectional.
Because
Cyclic : Cyclic compounds are chemical compounds having a basic non-linear structure. In other words, these are ring structures. One or more series of atoms in the compound is connected to form a ring structure.
Periodic : The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic number.
Unidirectional : compound is operating or moving in one direction only and it does not move in other direction.
Bidirectional : Capable of reacting or functioning in two, usually opposite, directions.
Thus, A change will only occur one time in unidirectional.
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