Equilibrium 4 Flashcards
what are electrolytes? non electrolytes
A substance that dissociates into ions is called electrolytes. Electrolytes can conduct electricity in aqeous solution
A substance that does not dissociate into ions. Its aqueous solution / molten state do not conduct electricity
types of electrolytes
(i) Strong electrolytes
- undergoes fast and complete dissociation into ions
NaCl, H2SO4
(ii) Weak electrolytes
- undergo slow and partial dissociation into ions
Carbonic acid, acetic acid, ammonium hydroxide
what is degree of dissociaion
alpha= total no of moles dissociated ions total no of moles taken
for strong electrolyte, alpha=1
for weak it is less than 1
The extent to which
ionization occurs depends upon the strength
of the bond and the extent of solvation of ions
produced.
what is the difference between the two trms dissociation and ionization
Dissociation refers to the process of
separation of ions in water already existing as
such in the solid state of the solute, as in
sodium chloride. On the other hand, ionization
corresponds to a process in which a neutral
molecule splits into charged ions in the
solution
what is arrhenius concept of acids and bases
acids are substances which have ionisable h+ and can dissociate to give h+ ion in solution. There are strong acids(ex) and weak acids( ex)
HX (aq) → H+(aq) + X–(aq)
or
HX(aq) + H2O(l) → H3O+(aq) + X –(aq)
Base is a substance that has OH- hydroxyl grp and can dissociate in aqueous solution to give oh- ions. there are strong and weak acids.
MOH(aq) → M+(aq) + OH–(aq)
how does H+ exist in solution
A bare proton, H+
is very reactive and
cannot exist freely in aqueous solutions. Thus,
it bonds to the oxygen atom of a solvent water
molecule to give trigonal pyramidal
hydronium ion, H3O+{[H (H2O)]+} (see box).
In this chapter we shall use H+
(aq) and H3O+(aq)
interchangeably to mean the same i.e., a
hydrated proton.
In aqueous
solution the hydronium ion is further
hydrated to give species like H5O2+, H7O3+,H9O4+
. Similarly the hydroxyl ion is hydrated
to give several ionic species like H3O2-, H5O3- etc
limitation of arrhenius concept
Arrhenius
concept of acid and base, however, suffers
from the limitation of being applicable only to
aqueous solutions and also, does not account
for the basicity of substances like, ammonia
which do not possess a hydroxyl group.
it does not account for acidict or basicity of substances like alcl3, bcl3 and nh3, ph3
what is bronsted-lowry concept
acid is
a substance that is capable of donating a
hydrogen ion H+
and bases are substances
capable of accepting a hydrogen ion, H+
. In
short, acids are proton donors and bases are
proton acceptors.
what is conjugate acid base pair
The acid-base pair that
differs only by one proton is called a conjugate
acid-base pair.
If
Brönsted acid is a strong acid then its
conjugate base is a weak base and viceversa. It may be noted that conjugate acid has
one extra proton and each conjugate base has
one less proton.
what are amphoteric or amphiprotic susbstances
some substances are amphoteric in nature, that is they have a tendency to act like proton donors and proton acceptor. these are called amphoteric substances or amphiprotic substances
eg: water
limitation of bronsted lowry concept
it couldnt explain the acid- base reactions which did inot involve proton transfer( ie do not take place in solution)
CaO+ SO3—> CaSO4
-substaces that do not have H+ b/c of which they cannot give a p+ but still are acids
why is NaOH not a base acc to bronsted lowry concept
It cannot accept protons but it is arrhenisus base because it can donate oh- grp
what is lewis concept of acids and bases
an acid as a
species which accepts electron pair and base
which donates an electron pair. Electron deficient species like AlCl3
, Co 3+
,
Mg2+ , etc. can act as Lewis acids while species
like H2O, NH3
, OH–
etc. which can donate a pair
of electrons, can act as Lewis bases.
Al bronsted lowry bases acts as lewis bases because they have lone pair but all bronsted-lowry acids do not act as lewis acids because they dont have proton.
Limitations of lewis concept
does not explain the behaviour of acids of protonic acids like HCl, HNO3, H2SO4 etc
- all acid base reactions do not involve coordinate bond formation
what are strong acids and strong bases acc to arrhenius concept
Strong acids like perchloric acid (HClO4
),hydrochloric acid (HCl), hydrobromic acid
(HBr), hyrdoiodic acid (HI), nitric acid (HNO3
)
and sulphuric acid (H2
SO4
) are termed strong
because they are almost completely
dissociated into their constituent ions in an
aqueous medium, thereby acting as proton
(H+
) donors. Similarly, strong bases like
lithium hydroxide (LiOH), sodium hydroxide
(NaOH), potassium hydroxide (KOH), caesium
hydroxide (CsOH) and barium hydroxide
Ba(OH)2
are almost completely dissociated into
ions in an aqueous medium giving hydroxyl
ions, OH
