Question

i need to know where to mark fhe equivalence point ans half equivalence point on my graph. i nedd to obtain the half equivalence point that will be my pKa value of the unknow acid.

PLEASE HELP

PH Vs Volume NaOH (mL) рн 0.00 5.00 20.00 25.00 10.00 15.00 Volume NaOH (mL)

Answer 1

. When and weak acid solution is titraated with Strong bave Naost, the remaining acid and the resulting Salt mixture behanes like a acidic baffero sffution, pH of this solution Cambe determined by Considering the attendansson's equation Of acidic buffer, pH e pka +log. Isallid [salti y Tacid - At half equivalence point ise, the amount of base (Narl) added is just half equivalent

of the acid present then the amount of salt foom is just equals to the amount of henreacted acid present in the solution. - [Salt] > Lacid] from equation , CPH pikatlog 7 It indicates at half equivalne point the pH value at this point is equals to the pka of the acid. PH me pas equivalencepoint 2 12.50ml Naast Valo 15 . Voleme Nash (mL) The equivalence point comresponds to the 12.50ml of Nant. Half equivalence point a 1250 x1 26.25mL Nast

Now, this 6:25mL of Nacht comesponds to the phralice in the yeaxis almost equal to 5.0. pka - (pH), 5.0 -*. pka valece of this acid - 5.0 .