can any one explain for me henderson-hasselblach equation?

Question

i cant under stand how its work
and what mean by the week acid is strong base then we add the strong base?
thanks for help in any way

Answer 1

The Henderson Hasselbalch equation is a mathematical rearrangement of the Ka expression

Ka = [H3O][A-]/[HA]

If you essentially take the -log of everything then you get the pKa, the pH and the log of the base (A-) over the parent acid (HA) in the equation.

The equation is used to determine the pH or the needed concentrations of the parent acid or conjugate base in order to create a buffer solution. The weak acid is the HA component in the equation. The "strong" base may be the conjugate base of the weak acid.

For example, if you are looking at H3PO4 as the parent acid, H2PO4-1 is the "strong" conjugate base.

Although sometimes you can do a final adjustment of pH using a strong acid (HCl) or strong base (NaOH) to get the final buffer solution correct.

If you are creating a buffer solution in lab. You would take a certain amount of the acid and mix it with a certain amount of the salt of a conjugate base in a solvent (typically water).

Answer 2

This equation is used to find pH for buffering solutions. Usually these buffereing solutions are comprised of a weak acid and a weak base. SInce weak acids and weak bases do not dissociate completely, the have a pKa value which is given. This is shown as the first expression in the H-H equation. In the second part, concentration of conjugate base over concentration of acid is taken into account. Log is taken to make in the form of whole big numbers. hope this helps!

Answer 3

It relates pH values to concs.