The document explains the principle of ionic strength, which quantifies the electrical intensity of ions in a solution using a specific formula involving molalities and valencies of the ions. It provides a calculation example for a solution containing NaCl and Ca(Cl)2 to illustrate how to determine ionic strength. The unit of ionic strength can be expressed in either molal or molar terms.

1. SUBMITTED BY
MAYUR HARSUKHBHAI MARVANIYA
MSc CHEMISTRY(SEM-2)
IONIC STRENGTH PRINCIPLE

2. PRINCIPLE
• The ionic strength I of a solution is a measure of the electrical
intensity due to the presence of ions in the solution.
• It is given by half of the sum of all the terms obtained by
multiplying the molality of each ion by the square of its
valency. we have
I=1/2(m1z1
2+m2z2
2+m3z3
2+……)
• Where m1,m2,m3….are molalities and z1,z2,z3…..are the
valencies of the various ions present in the solution.

3. PRINCIPLE
• The ionic strength I of a solution is a measure of the electrical
intensity due to the presence of ions in the solution.
• It is given by half of the sum of all the terms obtained by
multiplying the molality of each ion by the square of its
valency. we have
I=1/2(m1z1
2+m2z2
2+m3z3
2+……)
• Where m1,m2,m3….are molalities and z1,z2,z3…..are the
valencies of the various ions present in the solution.

4. • For a single electrolyte as for example potassium chloride or
zinc sulphate contains only two terms one for the cation and
other for the anion. Hence,
I=1/2(m+z+
2+m-z-
2)
• Where m+ and m- are the molalities and z+ and z- are the
valencies of the cation and the anion, respectively.
• The unit of Ionic strength is either Molal or Molar.

5. EXAMPLE
• The ionic strength of a solution which is 0.1 molal in NaCl and
0.01 molal in Ca(Cl)2, assuming complete ionization, may be
calculated as under:
• Molality of Na+ ion  m1=0.1 ;
• Molality of Ca2+ ion m2=0.01
Total molality of Cl- ion m3=0.1+0.2=0.12
accordingly,
I=1/2(m1z1
2+m2z2
2+m3z3
2)
=1/2(0.1x12+0.01x22+0.12x12)
I=0.13

6. refernce
• https://en.wikipedia.org/wiki/Ionic_strength#:~:te
xt=The%20ionic%20strength%20of%20a,the%20so
lubility%20of%20different%20salts
• https://chem.libretexts.org/Bookshelves/Analytical
_Chemistry/Supplemental_Modules_(Analytical_C
hemistry)/Analytical_Sciences_Digital_Library/Act
ive_Learning/Shorter_Activities/Ionic_Strength_a
nd_Activity
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