Solution:Concept- A chemical reaction is a process during which some chemical change is observed which may include the breaking of bonds, forming of new bonds, and generation of new compounds.
There are 5 types of chemical reactions-
● Combination/synthesis reactions
● Decomposition reactions
● Single-Replacement reactions
● Double displacement reactions
● Combustion reactions.
The reaction mentioned in the question: The reaction is reddish Mercuric oxide(II) solid decomposed upon heating into silver liquid mercury and colourless oxygen gas.
It is a chemical decomposition reaction as the mercuric oxide is broken down into mercury and oxygen.
Thus, is a Decomposition reaction.
Hence, the correct option is (2).