Pka Calculator

The pKa Calculator computes the pKa value, acid dissociation constant (Ka), percent dissociation, and buffer capacity of a solution based on the inputted pH, acid concentration, and conjugate base concentration.

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How to Use the pKa Calculator

Step 1: Input the pH Value

pH of Solution: Start by entering the pH value of your solution in the field labeled “pH of Solution”. This value should fall within the range of -2 to 16 and should be input as a number. Ensure that this field is filled because it is required, and note that you can enter decimal values with a step of 0.1.

Step 2: Input the Acid Concentration

Acid Concentration [HA] (M): In the field labeled “Acid Concentration [HA] (M)”, enter the concentration of the acidic component in your buffer solution. This value is required and should range between 0 and 100 M. The input can be as precise as 0.00001 M.

Step 3: Input the Conjugate Base Concentration

Conjugate Base Concentration [A-] (M): Next, input the concentration of the conjugate base in the “Conjugate Base Concentration [A-] (M)” field. This is also a required field, with acceptable values ranging from 0 to 100 M. Precision can similarly be to 0.00001 M.

Step 4: Review the Calculated Results

Once you have entered all the required inputs, the calculator will compute several important properties related to the buffer solution.

  • pKa Value: This is determined using the formula: pH + log10(acidConcentration / conjugateBaseConcentration). The result will be displayed as a number with three decimal places.
  • Ka (Acid Dissociation Constant): Calculated as 10 raised to the power of negative pKa. This value will be shown to six decimal places with the unit ‘M’ as a suffix.
  • Percent Dissociation: The percent dissociation is calculated using the formula: (conjugateBaseConcentration / (conjugateBaseConcentration + acidConcentration)) * 100. The percentage will be presented with two decimal places.
  • Buffer Capacity: This value is calculated as: 2.303 * (acidConcentration * conjugateBaseConcentration) / (acidConcentration + conjugateBaseConcentration). It is displayed with four decimal places and ‘M/pH’ as the suffix.

By following these steps, you can effectively use the pKa Calculator to determine crucial parameters of a buffer solution, enhancing your understanding and management of chemical systems.