Question

Be sure to answer all parts. Calculate the pH of 1.00 L of the buffer 0.94 M CHCOONa/0.92 M CH,COOH before and after the addition of the following species. (Assume there is no change in volume.) (a) pH of starting buffer: (b) pH after addition of 0.065 mol NaOH: (c) pH after further addition of 0.117 mol HCI: Prey 10 of 10

Answer 1

[Cho Na] = [sall] = [CH₂Coo] = 0.944 [Acid] - [eth e rot) = 0.92m Voluare of buffer - IL the buffer solution Contains 0.94 mol of the Coonat and 0.92 mel of Hero H. pka of the COOH = 4.7447 Apply Henderson hasselbalch equatich! We get- PH = pka + log (Sart] [Acid] a pH = pka + leglo. at L a d.ge a pH = (4.7447 4 0.00934) a. (pH = 4.754 PH of Stadting buffer = 4.754

If 0.065 mol NaOH is added then ados c + Cowbie g coil to form 0.065 mol the coona, CH₂COOH + NaOH = CH ₂ COONa+H2O So, no. of mol of CH₂ CH decreased by 0.065 mol and no. of mol of Cty Crona increased by 0.065 mol. No. of mol of CH ₂ COOH - (0.92 - 0.065) mol - 0.855 mol no. of mad of CH₂ Loona - (0.94 +0,065) ance - 1.005 mol volume of solution - 1L So [CH₂COOH = 0.855 (M) [CH₂ COONa] = 1.005 (M) PH = pka + leg (CH3COONa] Clz Col)

& PH = 4.7447 + lig (1005) 0.855 a, (pH = 4.814 0.117 molto Hee when added, then. I t combines with 0.117 mol of Hz Coo to form 0.117 mol CH₂ CroH. theos Nat & Hee - CH ₂ COOH + Nace. No. of mol of CH₂COOH = (8.92 +8.117) mol - 1.037 mol No. of mol of CH₂ Crona = (0.94_0.117) noe = 0, 823mol. Volume of solution - IL So [CH₂COOH) = 1.037 M. [esta crona] = 0.823 m The solution will be buffer solution,

PH - pka & dog [etlen) [the could de pH = 4.7 447 + log (0.823) L 1037) I, pH – 4. 6443 So, the after addition of pH of buffer 0.117 mal tee solution is 4.6443