Saturday, July 13, 2013

What is ionic strength of solutions and how is it calculated?

Ionic strength, μ, represents the total electrostatic forces contributed by ions in solution and can be calculated as shown in the following equation:

Where, Ci is the molar concentration of any ion in solution, and zi is its valence. Ionic strength is used to calculate activity and activity coefficient of ions and electrolytes in solution.

Example 1: Calculate ionic strength of a 0.02 M NaCl solution:

Answer:  μ = 0.5[(0.02 × 12 ) + (0.02 × 12 )] = 0.02 M

Example 2: Calculate ionic strength of a 0.02 M BaSO4 solution:

Answer:  μ = 0.5[(0.02 × 22 ) + (0.02 × 22 )] = 0.08 M

Example 3: Calculate ionic strength of a 0.02 M Na2SO4 solution:

 Answer:  μ = 0.5[(0.04 × 12 ) + (0.02 × 22 )] = 0.06 M

Example 4:  Calculate ionic strength of a solution containing 0.02 M NaCl and 0.02 M BaSO4:

Answer:  μ = 0.5[(0.02 × 12 ) + (0.02 × 12 ) + (0.02 × 22 ) + (0.02 × 22 )] = 0.10 M


 Note: only ionized species contribute to ionic strength in solution.

14 comments:

  1. Are you aware you have two question 2's?

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  2. i really thankful to you for these easy and appropriate examples for the related concept..

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  3. it is simple explanation, easy understand,.
    thanks

    ReplyDelete
  4. it is simple explanation, easy understand,.
    thanks

    ReplyDelete
  5. I really enjoyed your post.. Thnx for sharing.

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  6. You made it easy to understand with some good examples..thnx sir

    ReplyDelete
  7. ionic strength of 0.25 M CaCl2

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    Replies
    1. ionic strength=0.5[(0.25*2^2)+(0.5*1^2)]=0.75 M

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  8. how could i make a 10mM ionic strength cacl2 solution?

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    Replies
    1. 10mM=0.5[(x*2^2)+(2x*1^2)] solve for x then x=3.33mM. A 3.33 mM solution of CaCl2 has ionic strength of 10mM according to this calculation.

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  9. Calculate the ionic strength (M) of 50 ml of 0.75 % (w/v) NaCl solution?

    ReplyDelete

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