Question

2. What is the pH of a buffer containing 0.050 M NH3 and 0.050 M NHACI? 3. What is meant by buffer capacity? 4. Sketch a pH titration curve for the addition of 0.10 M HCl to 25.0 mL of a 0.10 M NH3 solution and indicate the "buffer zone".

Answer 1

(2) Hasselbalch we can equation use Henderson for a base as pot = pk + log [BH] -- [B] Here k is dissociation constant of basean FB++ ] is the concentration of conjugate acid of base B. [B ] is the concentration of Base. Now, Nth is a base whose conjugate acid is Ntyt ion. Se Henderson - Hasselbalch equation for Nts/Whice buffer system becomes : pot = pk + log Entut k for with = 1.8x10-5 So pk = - log K = - log (1.8 x 105) 3-4-4:745) = 4:745

Given concentration of the is EN]= _0.050M Also concentration of what ions is same as that of Nhace as Nrice - Nhut ce So, concentration of what is Entout] = o.osom Substituting all values in ① we get - POHz 4.745 + log (2:050) (o.oso) = 4.745 + logo = 4.745 to (Because log 1=0) poti24.745 Now we can calculate pt from pot using the relation PHLE poh14 - This pt = 14-pot pt = 14 - 4.745 pH = 9.255 - ~ 9.2 This pH of buffer containing o.osom Nth and o.oso M Nice is 9.2.