buffers

buffer solution

a system that minimises the pH changes when a small volume of an acid or a base is added

What is a buffer solution made up of

made up of a weak acid and its conjugate base

ways to form a buffer solution

reacting a weak acid with its salt or by partially neutralising a weak acid

how to form a buffer from a weak acid and its salt

Add the weak acid into solution and it partially dissacociates leaving some weak acid and if you also add its salt the salt dissolves to form its conjugate base

forming a buffer via partial neutralisation of a weak acid

Add an excess of the weak acid to an aqoeuse solution of an alkali so the weak acis is partially neutralised forming its conjugate base and some weak acid is also left behind

how does a conjugate base remove acid

If an acid is added the concentration of H+ ions increases and the H+ ions react with the conjugate base (A-) causing the equilbrium to shift to the left removing the H+ ions

how does a weak acid remove an alkali

When an alakli is added the concentration of OH- increases and the small concnetration of H+ ions react with the OH- forming water so the weak acid dissacociates shifting the equilibrium to the right restroing H+ concentration

calculating the pH of a buffer if HA is in excess

calculate the moles of HA left and the moles of A- formed. Then calculate [HA] and [A-]. You can then calculate [H+] using the equation [H+]= (Ka x [HA])/[A-]

calculating the pH of a buffer if the OH is in excess

first calculate [OH-] using the number of moles left and then use kw to find [H+] with the equation [H+]= (1×10^-14)/[OH-]

calculating the pH of a buffer if [HA]=[OH]

pH = pKa value of the weak acid

How does volume affect the pH of buffer solutions

The pH is constant as the ratio of [HA]/[A-] is the same

how to calculate the pH of a buffer with the amount of salt and acid and Ka value

calculate the moles of the acid and salt. Then the [H+]= Ka x n(acid)/n(salt). Then ph=-log([H+])