CHANGE IN pH OF AN ACIDIC AND BASIC BUFFER

CALCULATION OF PH OF ACIDIC AND BASIC BUFFER SOLUTION (HENDERSON-HASSELBALCH EQUATION)

Higher the amount of acid or base used to product a deinite change of pH in a buffer solution, higher will be its buffe capacity. Buffer capcity of solution is maximum under the following conditions [Salt] = [Acid](in acid buffer) [Salt] = [Base] (in base capacity] pH of buffer solution lies inthe range given below pH = pH_(a) +-1 In other words,any buffer solution can be used as buffer up to two pH units only, depending upon the value of pK_(a) or pK_(b) . A buffer is said to be efficient when pH = pK_(a) or pOH = pK_(b) Acifity of BF_(3) can be explained on the basis of which of the following concepts

The pH of basic buffer mixtures is given by : pH=pK_(a)+log((["Base"])/(["Salt"])) , whereas pH of acidic buffer mixtures is given by: pH= pK_(a)+log((["Salt"])/(["Acid"])) . Addition of little acid or base although shows no appreciable change for all practical purpose, but since the ratio (["Base"])/(["Salt"]) or (["Salt"])/(["Acid"]) change, a slight decrease or increase in pH results in. A weak acid HA after treatment with 12 mL of 0.1M strong base BOH has a pH=5 . At end point, the volume of same base required is 26.6mL K_(a) of acid is:

The Ph of basic buffer mixtures is given by : Ph=Pk_(a)+ log (["Base"])/(["Salt"]) whereas Ph of acidic buffer mixtures is given by : Ph = pK_(a)+"log"(["Salt"])/(["Acid"]) . Addition of little acid or base although shows no appreciable change in Ph for all practical purposes, but sicne the ratio (["Base"])/(["Salt"]) or (["Salt"])/(["Acid"]) changes, a slight decrease or increase in pH results. The ratio of pH of solution (I) containing 1 mole to pH of solution (II) containing 1 mole of CH_(3)COONa and 1 mole of acetic in one litre is :

A solution capable of maintaining its pH relatively constatn, when either excess acid or excess base is added, is said to be buffered While it is not usually considered a buffered solution, a concentrated solution (10^(-2) M and higher) of a strong acid or stong base is buffered against large changes in pH when acids or bases are added. Buffered solutions are usually those containing a wealk acid and a salt of that weak acid or a weak base and the salt of that weak base. For example a solution containing HAc and NaAC resists large change in pH when acid or alkali is added. For a buffer solution Buiffer capacity is defined as the number of moles of a strong acid or a strong base that causes 1 of the buffer to undergo a 1 unit change in pH. Buffer capacity is maximum when the molar ratio of the two components is unity and the buffer solution is considerred good. The least change in pH on adding 0.01 mol of HCI to 1 litre of conc. HCI solutiions will be in case of:

Buffer Action Of Acidic And Basic Buffer

Basic Buffer || pH Determination Formula || Buffer Action OF Acidic Buffer || Solved Numerical Class illustration and Buffer Capacity

The pH of basic buffer mixtures is given by : pH=pK_(a)+log((["Base"])/(["Salt"])) , whereas pH of acidic buffer mixtures is given by: pH= pK_(a)+log((["Salt"])/(["Acid"])) . Addition of little acid or base although shows no appreciable change for all practical purpose, but since the ratio (["Base"])/(["Salt"]) or (["Salt"])/(["Acid"]) change, a slight decrease or increase in pH results in. Mole of HCI required to prepare a buffer solution of pH=8.5 with 0.1 mole of NaCN in one litre solution is: (pK_(a) for CN^(-)=4.61)

The solution which consumes [H^(+)] or [OH^(-)] or both simultaneously from externally added base in order to give negligible change in pH , is known as buffer solution. In general, the solution resists the change in pH. Buffer solution does not mean that there does not occur a pH change in pH. Buffer solution des not mean that there does not occur a pH change at all. It implies the pH change occurs but in neglibible amount. There are two types of buffer (i) Acidic buffer: it is a mixture of weak acid and its salt acid strong base. (ii) Basic buffer : It is a mixture of weak base and its salt with strong acid. pH of 0.01 M (NH_(4))_(2)SO_(4) and 0.02 M NH_(4)OH buffer ( pK_(a) of NH_(4^(+)) = 9.26) is