Question

Construct a rough plot of pH versus volume of added base for the titration of 50 mL of 0.060 M HCN with 0.075 M NaOH. K_a = 4.0*10^-10 for HCN

Figure 17.11.

(a) What is the pH before any NaOH is added?

(b) What volume of base, in milliliters, is required to reach the equivalence point?

(c) What is the pH at the equivalence point?

(d) What indicator would be most suitable to determine the endpoint?

bromcresol purple, bromocresol green, Alizarin yellow GG, or Bromthymol blue

Answer 1

some 0006M HEN Vs .0.075M NaOH. "Ka-4xlulo las Vian - O me HON (aq) = 0.06M H+ (aq) + Cão (aq), (ka).- 4 xlorlo, Ab to a Ab ta teq 10.06-al 10.06 a Сf]Сс) CHCN] чхо- lo Albrezimation ús valid as ka û very less xxx a 0:06 uxlolo u² = 0.24x1510 Havoizy x1017 CHO]= = 0.489 x 105m pH = -log (At] = -log(0.489 x103) = 5.31 (6) At equivalence point, se millies of Hena mollier of Noor 1 x Vanx (n-factor of = Macore x VNoon x n-factor of Nao4 HEN) MCN ^ "HCN No. of furnishable He ran al (So, n-factor of Hen is no. of furnishable of Con is 13 Son-factor of Nook al 50 x0.06x10.075 t Viceret yo me a unaon

lo pH at Equivalence Print, I HEN + oH - CN - Soxo.o6 90 tho, reg o Ka 481510 15114 248104 4ox 0.075 Neutralisatia мин I tebe ex - Карал, 4 см M (cenzungente Base of weak aid HEN) (Activity of bure liquid [EN] [H₂O) = 4X104 .. [ore ] [ren] in unity, -24 X 704 30 You? 1,0913 x 10-2M 02. - [50] poko-bay.com Dc - Coglo. One X153) = 3.04 1 pH > 14 - pola 14 -3 04 = 10.96) Equivalence read 10) so, Alizarin Yellow qq has Colour trausstion (1002 - 12. and the Yellow 49 has Colour trausation pH range (CTOR) [1002-12 and the equivalence pH ů 10,96 which pH. - lies in CTPR of Alizanın Yellow GG so it is a suita for this weak acid/ strung Bure Tustration, 1. Indleator

Rough Plot of weak acid (HCN) us strong Bate 1 Titration curre Nach 12f9 - - - (Equivalence 10.96 - = =- - Equivalence Porint p4 ) Colour I & Trausition ph range of Alizarin yellow aq. hice added at i Vnook equivalence parint Naon Home equivalence perint lies in CTRR of Alizarin Yellowęq. That's It is a suntable Indicator for this tetration.