Ammonium cyanide, NH^+CN^-, is a salt of both a weak acid (Ka= 5.6e-10) and weak

Question

Ammonium cyanide, NH^+CN^-, is a salt of both a weak acid (Ka= 5.6e-10) and weak base (Kb= 1.6e-5). What are the concentration of all species in solution and what is the pH of a 0.10 M aqueous solution? NH4^+CN^- ---> NH4^+ (aq) + CN^- (aq) . xt Due: Friday June 26h 4pm in My Office HEB2124 Ammonium cyanide, NH CN, is a salt of both a weak acid (Ks = 5.6-10-10) and weak base (K = 1.6. 10-5). What are the concentrations of all species in solution a a 0.10 M aqueous solution? b1.6.105). What are the nd what is the pH of NH4+CN. NH4"(aq) + CN (aq)

Explanation / Answer

pKa of weakacid = -log ka

                 = -log 5.6*10^-10 = 9.25

pKb of weakbase = -log kb = -log 1.6*10^-5

                = 5-log 1.6 = 4.796

pH = 7+1/2[pKa-pKb]

   = 7+1/2[9.25-4.796]

pH = 9.227

[H+] = 10^-pH = 10^-9.227 = 5.93*10^-10.

[OH-] = 10^-pOH = 10^- 4.773 = 1.6865*10^-5.

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