Question

What are simple and complex reactions?

Answer 1

Hint: A chemical reaction occurs when a chemical or chemicals convert into another substance. And Complex reaction mechanisms can consist of a number of electron transfer steps, with some chemical steps preceding or succeeding the electron transfer steps or taking place in between them.

Complete answer:
Simple reactions-
A chemical reaction occurs when a chemical or chemicals (the reactants) convert into another substance (the product). These reactions happen during cooking, cleaning, driving, and processes occurring inside your body, among others. There are four main types of chemical reactions: synthesis, decomposition, single replacement, and double displacement.
Complex reactions-
The term complex reaction simply refers to a reaction whose mechanism comprises more than one elementary step. Such an experimentally determined rate law may be compared with the predicted rate law for a given mechanism in order to determine whether the proposed mechanism is indeed the correct one.
The chemical kinetics is classified into three types, mathematical, detailed, and applied kinetics, while their elementary reactions are described as unimolecular, bimolecular, and termolecular reactions.

Note:
In addition to the four main types of simple chemical reactions, there are other important categories of reactions and other ways to classify reactions. Here are some more kinds of reactions-
acid-base reaction: $HA + BOH \to {H_2}O + BA$
neutralization reaction: acid $ + $ base $ \to $ salt $ + $ water
oxidation-reduction or redox reaction: one atom gains an electron while another atom loses an electron.
isomerization: structural arrangement of a molecule changes, although its formula remains the same hydrolysis: $AB + {H_2}O \to AH + BOH$