1. Notebook: raja
Created: 19-04-2018 12:27 PM Updated: 19-04-2018 01:37 PM
Author: laxmanss227@gmail.com
Tags: chemistry, electro chemistry
Q1) define ionization ?
Q1) define ionization ?
ans) Ionization (Ionisation), is the process by which an atom or a molecule acquires a negative or
positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical
changes
Q2) Define degree of ionization?prove that ionization increases when dilution increases
ans) the degree of ionisation or the degree of dissociation represented by α is the ratio of the number
of molecules dissociated to the number of molecules initially taken.
It is useful in determination of strength of acids or bases and determine the extent of reaction in
forward or reverse direction and many more uses.
Dissociation increases with dilution because each molecule requires certain amount of energy to break
bonds. Consider HCl, it needs a certain amount of energy to dissociate into H+ and Cl-. We dissolved a
certain amount of HCl in water, and HCl dissociates utilising the energy from water(water also
dissociates into H+ and OH-). After some time only limited amount of water molecules will remain
undissociated,and they will be unable to provide enough energy for dissociation. Once you add more
water there will be more supply of energy to carry out dissociation. Thus degree of dissociation
increases with dilution
Q3)explain PH value ?
ans) PH is a numeric scale used to specify the acidity or basicity of an aqueous solution. A measure of
acidity or alkalinity of water soluble substances (pH stands for 'potential of Hydrogen'). A pH value is a
number from 1 to 14, with 7 as the middle (neutral) point. Values below 7 indicate acidity which
increases as the number decreases, 1 being the most acidic
Q4) define ionization potential and factor affecting ionization potential?
ans)The amount of energy required to remove the most loosely bound electron, the valence electron, of
an isolated gaseous atom to form a cation.
Factors affecting Ionisation potential
(i) Atomic radius: The values of ionisation potential of an element decreases as its atomic radius
increases. ...
(ii) Effective nuclear charge: ...
(iii) Penetration effect of orbitals: ...
(iv) Shielding or screening effect: ...
(v) Stability of half−filled and fully-filled orbitals:
Q5)ionization potential of B is less than Be and ionization potential of O is less than N.Explain its reason.
ans) (1) The electrons in the 2s orbital are already paired and hence it is quite a stable configuration for
the beryllium atom. ... Beryllium has a higher Ionisation energy than boron because of increased
2. stability due to half filled and fully filled orbitals
(2) Oxygen has low ionisation energy (than that of nitrogen). It is due to an electron being added to an
already half full orbital in oxygen, which results in electron electron repulsion, which will lower the
ionisation energy. ... And we know half filled orbitals are more stable due to more exchange energy
Q6)explain the buffer action of acidic buffer solution.
ans)Let us consider the buffer action of acidic buffer containing CH3COOH and CH3COONa. Acetic acid
dissociates to a small extent whereas sodium acetate is almost completely dissociated in aqueous
solution as:
CH3COOH + H2O CH3COO‾ + H3O+ —————-1
CH3COONa ———-> CH3COO‾ + Na+
By common ion effect, the ionization of CH3COOH is further suppressed. Thus in the solution, there are
excess of acetate ions and a small amount of H3O+ ions.
When a few drops of an acid are added to the above mixture solution ,the H3O+ ions given by the acid
combine with CH3COO‾ ions to form weakly ionized molecules of CH3COOH.
CH3COO‾ + H3O+ ———–> CH3COOH + H2O
The H3O+ ion concentration and hence the pH of the solution remains almost constant.
When a few drops of a base are added, the OH‾ ions given by the base combine with the H3O+ ions
already present to form weakly ionized molecules of H2O.
H3O+ + OH‾ ———–>2H2O
As H3O+ ions are consumed ,the equilibrium 1 shifts towards right. Thus more of CH3COOH dissociates
to make up the loss of H3O+ ion. Hence the H3O+ ion concentration or pH of the solution does not
change.
