Enter the desired pH, total buffer volume (L), and total buffer concentration (M) into the calculator to determine the required moles of monobasic and dibasic phosphate.
Related Calculators
- Buffer Capacity Calculator + Formula
- Ph To Oh- Calculator
- pH ↔️ pOH Calculator
- Moles To Ml Calculator
- All Chemistry Calculators
Phosphate Buffer Formula
The Henderson-Hasselbalch equation is used to calculate the ratio of dibasic to monobasic phosphate.
pH = pKa + log\left(\frac{[Dibasic]}{[Monobasic]}\right)- Where pH is the desired pH level of the buffer solution
- pKa is the acid dissociation constant (approx. 7.20 for phosphate buffer)
- [Dibasic] represents the moles of dibasic phosphate
- [Monobasic] represents the moles of monobasic phosphate
To prepare the buffer, use the Henderson-Hasselbalch equation to determine the ratio of the two phosphate forms and calculate the required moles of each.
What is a Phosphate Buffer?
Definition:
A phosphate buffer is a solution designed to resist changes in pH, commonly used in biochemical and laboratory applications. It is prepared by mixing monobasic and dibasic phosphate salts.
How to Prepare a Phosphate Buffer?
Example Problem:
The following example outlines the steps and information needed to prepare a phosphate buffer solution.
First, determine the desired pH of the buffer. For instance, if you aim for a pH of 7.40, enter this value into the calculator.
Next, specify the total buffer volume and the total buffer concentration. In this example, consider preparing 1 L of buffer at a concentration of 0.1 M.
Finally, calculate the required moles of monobasic and dibasic phosphate using the equation above:
pH = pKa + log([Dibasic] / [Monobasic])
The calculated values will indicate the precise amounts of each phosphate form needed to achieve the desired pH.
FAQ
What factors can affect the pH of a phosphate buffer?
The pH of a phosphate buffer can be influenced by temperature, ionic strength, and the purity of the phosphate salts used.
Can this calculator be used for buffers with different pKa values?
This calculator is designed for phosphate buffers with a pKa of 7.20; adjustments are needed when working with other buffering systems.
How do I modify the buffer preparation for different volumes or concentrations?
Simply enter the desired total buffer volume and concentration into the calculator to recalculate the required moles of each phosphate component.