Question

What is the difference between hydrolysis and hydration?

Answer 1

Hint : Both the terms relate to action of water molecules. One adds water to a molecule while another cuts a molecule using water.

Complete step by step solution :
Let’s start with hydration. The addition of water molecules to another molecule is termed as hydration. It has many uses in organic chemistry such as the synthesis of alcohol and also in inorganic chemistry such as production of metallic hydroxides and many more.
We first take a look at organic chemistry. The synthesis of alcohol from alkyl halides is the most common process. The reaction is as follows:

$RX+{{H}_{2}}O\to ROH+HCl$
Where $X=Cl\ And Br$(halogens)

This is a bimolecular nucleophilic substitution reaction or${{S}_{N}}2$, meaning there are two reacting molecules in the rate determining step.
You must have seen some compounds like$CuS{{O}_{4}}.5{{H}_{2}}O$. These are called hydrated double salts. They retain water molecules in their crystal lattice but are not bonded with them covalently or electrovalent. Hydration on copper sulphate solid crystals converts them into this form. The water molecules escape when the double salt is dissolved in water.
We now move on to hydrolysis. Breaking down this word we get “hydro” meaning water and “lysis” meaning breaking. In other words it simply means to break or cut molecules with the help of water. The most common example is the hydrolysis of esters. The esters have a general formula of $RCOOR'$. Both the “R” groups can be similar or different. Upon hydrolysis, esters separate into their constituent alcohols and carboxylic acids. The reaction is as follows:

$RCOOR'\xrightarrow[{{H}^{+}}]{H2O}RCOOH+R'OH$

This reaction is either carried out in basic or acidic medium which act as catalysts. The mechanism is similar in both the cases where ${{H}_{2}}O$breaks $RCO-OR'$bond and then converts them into acid and alcohol.
Hydrolysis reactions are also the ones which break the bonds between complex sugar moieties converting them into smaller units.
Both hydration and hydrolysis are important reactions inside living organisms.

Note : The addition of water molecules at a molecular scale to any compound is said to be hydration. Adding water in any other way where the ${{H}_{2}}O$ molecule is not integrated inside a molecule is not referred to as the same. And this applies for hydrolysis too.