If I have 1.00 mM NaCl and 4.32 mM NaCl, how do I calculate the ionic strengths of each? Thanks
In a 1:1 salt such as NaCl the ionic strength is the same as the molarity.
http://en.wikipedia.org/wiki/Ionic_strength
To calculate the ionic strength of a solution, you need to know the concentration of each ion in the solution and their respective charges. In this case, we are dealing with the sodium chloride (NaCl) solution.
The ionic strength is a measure of the total concentration of ions in the solution and is calculated using the formula:
Ionic Strength (I) = 1/2 ∑(ci * zi^2)
Where:
- I is the ionic strength
- ∑ represents the sum of
- ci is the concentration of each ion in the solution
- zi is the charge of each ion
In the case of NaCl, we have only one ion, Na+ (sodium cation), and Cl- (chloride anion), each with their own concentration.
For the 1.00 mM NaCl solution:
- ci = 1.00 mM (concentration of NaCl)
- zi = 1 (charge of Na+ and Cl-)
Plugging these values into the formula:
I1 = 1/2 * [(1.00 mM * 1^2) + (1.00 mM * (-1)^2)]
I1 = 1/2 * [1.00 mM + 1.00 mM]
I1 = 1/2 * 2.00 mM
I1 = 1.00 mM
For the 4.32 mM NaCl solution:
- ci = 4.32 mM (concentration of NaCl)
- zi = 1 (charge of Na+ and Cl-)
Plugging these values into the formula:
I2 = 1/2 * [(4.32 mM * 1^2) + (4.32 mM * (-1)^2)]
I2 = 1/2 * [4.32 mM + 4.32 mM]
I2 = 1/2 * 8.64 mM
I2 = 4.32 mM
So, the ionic strength of the 1.00 mM NaCl solution is 1.00 mM and the ionic strength of the 4.32 mM NaCl solution is 4.32 mM.