What is molecule? and what is the molecular formulae?

molecule is a group of atom .Molecular formula is the presentation of symbols of a molecules in  a systematic way.

Explanation:

For eg ; O is the 1 atom of oxygen and HCl is the molecules of hydrochroric acid.

     Examples of the molecular formula;

   hydrogen + chroride =hydrogenchroride

= 2H + 2Cl =2HCl

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

pv=nrt

explanation: