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How to Calculate Buffer Preparation

Calculating buffer preparation requires a solid grasp of chemistry fundamentals, including titration to a desired pH and balancing equations. Students who have not completed a first-year chemistry course should not attempt to calculate buffer preparation, and preparation needs to be completed in a laboratory with adequate supplies for weighing chemicals and measuring pH levels. Buffer preparation calculations are attainable for acid-base pairs in monoprotic systems with minimal effort.

Things You'll Need

Paper
Pencil
Calculator
Ring stand with clamp
Erlennmeyer flask
Beaker
Pipet

Instructions

Acid-Base Pair Buffers
- 1
  Determine the principal components of the buffer system and identify the cojugate acid-base pair.
- 2
  Write out the equilibrium to reflect the desired pH using the Henderson-Hasselbalch equation pH=pK + log ([A-]/[HA]) where HA is the acid that will donate the the proton to the base, A- is the conjugate base that results after the acid donates its proton and pK is the remainder of the desired pH less the log of A-/HA.
- 3
  Solve the equation and test your calculations by converting your equation to a proportional ratio of 1 mole of the conjugate base and conduct a lab test using the scaled-down equation.
- 4
  Prepare 1 mole of the base in an Erlennmeyer flask. Titrate the solution to the desired pH by adding the requisite amount of the conjugate acid to the flask using a pipet. Measure the pH periodically and adjust original calculations if necessary.

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