Originally posted by Kahynickel:
NaCl dissolves in water without any chemical reaction
(hydration), while SiCl4 is hydrolysed by water. Can we say that
ethanol which soluble in water undergoes hydration?? I think that
hydration is the dissolution of ions in water without chemical
reaction. ethanol has no ions i aqueous solution so ethanol in
water in neither hydration nor hydrolysis.
Mostly Covalent molecules are said to be hydrolysed and those
having ionic plus some covalent character such as MgCl2 up to
Awaiting for ur thoughts.
Hydrolysis refers to chemical reaction with water (in which either the water molecule or the other reactant, or both, is 'lysed' or broken up), and a chemical reaction is defined as one in which a sigma bond (including dative bonds) is formed or broken.
Hydration is a subset of solvation (in which the solvent is water), and solvation refers to any physical (non-chemical) interaction between the solute and the solvent, eg. hydrogen bonding, ion - permanent dipole interactions, etc.
As such, ethanol (as a solute in the minority) may be considered to undergo hydration (with water as a solvent in the majority), rather than hydrolysis (as no sigma bonds are formed or broken), when ethanol accepts and donates hydrogen bonds from and to water. But if you prefer not to see or label it as hydration, it won't be an issue for A level purposes, as Cambridge won't specifically ask in this context.
1 related point to take note of : For the 2 equations that AlCl3
(s) dissolved in water participates in to generate an acidic solution as required by all A level syllabuses, the 1st equation where AlCl3
(s) dissolves in water to generate [Al(H2
(aq) and 3Cl-
(aq), while this may technically be considered hydrolysis (since Al3+
has sufficiently high cationic charge density to accept dative bonds from H2
O ligands, rather than simply ion - permanent dipole interactions), is more usually labeled as hydration, in order to avoid confusion with what occurs next, ie. the 2nd equation, which is even moreso characteristically a hydrolysis reaction (and hence correctly labeled as such),
O â‡Œ [Al(OH)(H2