groundbreakers
10 facts on ...
BUFFERS
In this ongoing series we ’ ve covered acid , bases & salts ...
Let ’ s talk about buffers this time :
BUFFERS ARE MADE by combining a weak acid in solution with its conjugate ( weak ) base . by Philip McIntosh
THE TERM BUFFER is used in a lot of ways . In general usage , it suggests a cushion or barrier of some kind between two zones . Chemically , the meaning is analogous .
IN CHEMISTRY , a buffer is a solution that resists a change in pH . So , it sort of “ cushions ” a solution against large or rapid variations in acidity or basicity .
A WELL BUFFERED solution can take a reasonable addition of strong acid or base , and react in such a way as to take H + or OH- ions out of solution , thus keeping the acid-base balance relatively stable .
A GENERIC ACID , HA has a conjugate base of A- , where H is a proton to be released as H + ( that makes it an acid ) and A- is a counter ion ( which could be a lot of things ).
BUFFERS THEMSELVES can either be acidic ( pH < 7 ) or basic ( pH > 7 ).
IF A STRONG ACID is added to this solution , it will preferentially react with the free PO 4-3
( mostly from the Na 3PO 4 ) rather than water to make more of the weak acid H 3PO 4 instead of H 3O + so the pH doesn ’ t change much at all .
IF A STRONG BASE ( OH- ) is added to the solution , the weak acid ( H 3PO 4 ) will release one of it ’ s protons to combine with the OH- to create water ( H 2O ) and again the pH doesn ’ t change much at all .
AN EXAMPLE : Phosphoric acid ( H 3PO 4 ) is a weak acid where there are three possible H + ions to be released ( the H part ) and the PO 4-3 ( that ’ s the A- part ). If we combine it in solution with sodium phosphate ( Na 3PO 4 ) we provide some sodium ions and more of the phosphate PO 4-3 ( that ’ s the conjugate base ).
IN THE ABOVE example , only a little of the H 3PO 4 ionizes ( because it is a weak acid ) and much of the H 3PO 4 remains un-ionized in solution .
162 groundbreakers