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Buffer solutions are aqueous solutions of a weak acid with its conjugate base, or a weak base with its conjugate acid.
Buffer solutions are incredibly useful as they have the ability to maintain a stable pH balance and resist change, even when a strong base or acid is introduced. pH is a measure of hydrogen (H+) ions in a solution.
About Buffer Solutions
Buffer solutions are also known as pH buffers or hydrogen ion buffers because they effectively ‘rebuff’ any changes to the pH level when a strong acid or base is added. Buffer solutions keep the pH at an almost constant level because they contain an equilibrium between the acid (HA) and its conjugate base (A-), or between the base and its conjugate acid.
Buffers solutions can be divided into two types – acidic and alkaline.
- An acidic buffer solution has a pH less than 7 and is typically made from a weak acid and one of its salts.
- An alkaline buffer solution has a pH greater than 7 and is made from a weak base and one of its salts.
This doesn’t mean that buffer solutions have a neutral pH, just that they have a balanced pH. They maintain this balance and prevent external influences from changing the pH and potentially harming whatever it is the buffer solution is being used for.
How Do Buffer Solutions Work?
A buffer solution is produced by combining a weak acid with its conjugate base, or a weak base with its conjugate acid. What are conjugates? Over to Wikipedia…
“A conjugate acid is a chemical compound formed by the reception of a proton by a base—in other words, it’s a base with a hydrogen ion added to it. A conjugate base is what remains after an acid has provided a proton during a chemical reaction.”
It’s the conjugates that make buffer solutions particularly effective as they create the pH balance that is so difficult for even strong acids and bases to break down.
In any solution, the addition of an acid increases the concentration of hydrogen (H+) ions, while the addition of a base increases the concentration of hydroxide (OH-) ions. The pH is the ratio between these two types of ion. A buffer solution added to the mixture absorbs either extra H+ or OH- ions, maintaining the pH balance.
Buffer solutions do have thresholds. If enough strong acid or base is added to the solution, the pH will ultimately change. This is known as the buffer capacity.
Uses of Buffer Solutions
Many chemical reactions need a constant pH to work properly, so buffer solutions have many uses. Industrially, buffer solutions are used in:
- Fermentation
- Dyeing fabrics
- Chemical analysis
- Household products such as washing up liquids
- Personal hygiene products such as soap
- Calibrating equipment
Buffer Solutions in Nature
Buffer solutions also occur naturally. Perhaps the most important example of this is in our own bodies, where our blood has a normal pH of 7.35. It needs to be maintained at this level in order for our bodies to function properly, so our blood contains a ‘buffer’.
