O - Buffers Flashcards
What is a buffer?
A solution that resists changes in pH when small amounts of acid or base are added, or it’s diluted.
What are acidic buffers made from?
A weak acid and one of its salts.
What is the pH of acidic buffers?
Less than 7.
Why are buffer really handy in everyday life?
1) Shampoos contain a pH 5.5 buffer.
2) Blood needs to be kept at pH 7.4 and is buffered using carbonic acid.
3) Biological washing powders contain buffers.
4) Cells need a constant pH to allow the biochemical reactions to take place.
5) Buffers are used in food products to control the pH.
Why do shampoos contain buffers?
They contain a pH 5.5 buffer.
Soap gets your hair squeaky clean, but it’s usually very alkaline and alkalis tend to make hair look dull. So adding a slightly acidic buffer will keep your hair looking shiny.
Why does blood have/need a buffer?
Blood needs to be kept at pH 7.4 and is buffered using carbonic acid.
The levels of H2CO3 are controlled by respiration. By breathing out CO2 the level of H2CO3 is reduced as it moves this equilibrium to the right. The levels of HCO3^- are controlled by the kidneys with excess being excreted in the urine.
Why do biological washing powders contain buffers?
To keep the pH at the right level for enzymes to work.
Why do cells contain buffers?
They need a constant pH to allow the biochemical reactions to take place. The pH is controlled by a buffer based on the equilibrium between dihydrogen phosphate ions and hydrogen phosphate ions.
Why are buffers used in food products?
To control pH. Changes in pH can be caused by bacteria and fungi and cause food to deteriorate. A common buffer is made using sodium citrate, which sets up an equilibrium between citrate ions and citric acid. Phosphoric acid/phosphate ions and benzoic acid/benzoate ions are also used as buffers.
What do you need to know to be able to calculate the pH of a buffer solution?
The Ka of the weak acid and the concentrations of the weak acid and its salt.
