simple concept about the applications of conductance measurement

1. Presented by : Sara Anwar
Topic : “APPLICATION OF CONDUCTANCE
MEASUREMENT”

2. 1: Determination of degree of dissociation of weak electrolyte
2: Determination of ionization constant of acids
3: Determination of solubilty product (ksp ) of sparingly soluble salt
4: Calculation of ionic product of water
5: Conductometric titration

3. Determination of degree of dissociation:
• “Degree of dissociation is the fraction of the total number of molecules
dissociated into ions.”
Degree of dissociation (ᾳ) = No. of molecules dissociated into ions
Total no. of molecules present
• No. of molecules dissociated is directly proportional to
conductivity of the molecules.
• No. of molecules dissociated in to ions λm
c ( molar conductivity
at a particular concentration.)
• Total no. of molecules λm
∞(molar conductivity at infinite
concentration)
ᾳ(degree of dissociation) = λm
c / λm
∞
1:

4. 2:Determination of ionization constant of acids:
• The acid ionization constant, also called the 'acid dissociation
constant' or 'acidity constant,' is a measure of how much of the acid
is deprotonated (which is when it's unbound to a hydrogen),
compared to molecules still bound to a hydrogen.
• example :acetic acid
(left) (right)
CH3 COOH CH3 COO_ + H+
at time 0 C 0 0
t C-Cᾳ Cᾳ Cᾳ
[Cᾳ is dissociated part ]

5. According to the law of mass action :
“The rate of chemical reaction is directly
proportional to the product of active masses of
reactiong substances.”
Ka = Cᾳ Cᾳ
C(1-ᾳ)
Ka =CᾳCᾳ
C(1-ᾳ)
Ka =Cᾳ2
1-ᾳ [ᾳ is of
dissociation ]

6. 3)Determination of solubility product (ksp) of
sparingly soluble salt :
Solubility product:
• When a sparingly soluble salt is placed in water, a very small amount
of the salt dissolves in the water and a solution is formed. The
solubility product, Ksp, determines the equilibrium that exists
between the sparingly soluble salt and the ions that are dissolved in
water
Example :
AgCl (s) Ag+
(aq) + Cl-
(aq)

7. Ksp = [Ag+ ][Cl- ]
if the s is the solubilty of AgCl then :
[Ag+ ] =s & [Cl- ]=s
Ksp =(s) (s)
Ksp =s2

8. 4)Calculation of ionic product of water:
• Water has electrical conductivity, hence it must undergo dissociation .
Dissociation of pure water to a very little extent into H+ and OH – ions by
itself is called as self ionization of water .
• Water is very weak electrolyte . In water an equilibrium between ions an
unionized water molecules exists as :
H2O H+ + OH-
H+ + H2O H3O+
the net reaction is
H2O + H2O H3O+ +OH-

9. • Applying the law of mass action to above equilibirium , we have
kW =[H3O+][OH-]/ [H2O]2 (1)
Now water is very weak electrolyte . It dissociate in a very small
amount . Hence practically the concentration of unionized water is
almost the same as starting concentration .hence H2O =1=constant .
• similarly that H+
(aq) actually refers to a hydroxonium ion. Therefore the
1st equation becomes:
kW [constant]=[H+][OH-] (2)
KW =[H+ ][OH- ]
the relation is known as the ionic product of water

10. • When small amount of acid is added to water , the concentration of
[H+ ] increases and the concentration of [OH- ] decreases
• When small amount of alkali is added to water , [OH- ] ions
concentration becomes higher than that of [H+ ] ion concentration
• In neutral solution, [H+ ] and [OH- ] ion concentration are equal
• Thus the concept of ionic products of water helps us in classifying the
aqueous solution as an acid , base or neutral.

11. 5) CONDUCTOMETRIC TITRATION
• “The determination of end point of a titration by the means of
conductivity measurements are known as conductometric titration”
TYPES OF CONDUCTOMETRIC TITRATIONS
• acid-base titration
• Precipitation titration
• Replacement titration
• Redox ( oxidation-reduction) titration
• Complexometric titration

12. -
-
-
-
Burette (strong acid
e.g HCL)
Electrodes
Battery +
__
Beaker (strong
base e.g NAOH)
CONDUCTOMETER
Acid – base titration :
HCL
NAOHH2O+NACL

13. HCL
NAOH
1
2
3

14. FACTORS AFFECTING CONDUCTIVITY:
• Size of ions
• Temperature
• Charge of ions
• Numbers of ions

15. Principals:
• Conductometry is the ability to measure the ability of electrolyte
carry current .
• Conductrometry is depends on the ions present in the electrolyte .
• As the number of ions in the solution decreases the conductivity
decreases and vise versa .
• The point from which the conductance remains constant is
neutralization point which indicates the end point of reaction .

16. Advantages of the conduct metric titration :
• No need of indicator
• Colored or dilute solution can be used for titration .
• End point can be determined accurately.

17. THANK YOU