Question

1) Cyanide salts such as Sodium Cyanide (NaCN) are among the most rapidly acting of all known poisons and act by inhibiting respiration. a. Determine the pH of a solution of 0.054M Sodium Cyanide (NaCN) (assuming complete dissociation) and state whether sodium cyanide is an acidic basic or neutral salt (Ka HCN = 4.9x10-9) (6 marks)

Chemistry Class

Answer 1

N + H₂O I 0.054M c -a E 0.054-x HEN + OH- 0 0 +2 +x 2 x [HCN] [or [CN- 1x10-14 ka x Kb I KW. 4.9x109 x K6 = Kb = x 10-14 4.9 x10-9 = 2.04 xlo 2.04 x 10-6 = [HEN] [or] [N ] x² 0.054-X. 2.04 x 10-6 = x = 10.054 x2.04x100 [x < < 0.054] X = 3.32x 109M = [or] =[HCNJ POH -_-loglom) -log (3.32 x104) pOH = 3.48 PH = 14-POH 14-348 = 10-52 IPH = 10.52 Nach is Basic salt.