Question

# 23. What is the pH of an aqueous solution made by combining 38.64 mL of a...

23. What is the pH of an aqueous solution made by combining 38.64 mL of a 0.4904 M ammonium chloride with 39.77 mL of a 0.3735 M solution of ammonia to which 4.670 mL of a 0.0772 M solution of HCl was added?

41. In a titration of 40.09 mL of 0.3795 M ammonia with 0.3795 M aqueous nitric acid, what is the pH of the solution when 40.09 mL of the acid have been added?

71. what is the molar solubility of barium fluoride?

23) pH of basic buffer =14 - (pkb+log(NH4Cl+HCl/NH3-HCl))

pkb of NH3 = 4.75

no of mol of NH4Cl ADDED = 38.64*0.4904 = 18.95 mmol

no of mol of NH3 added = 39.77*0.3735 = 14.85 mmol

no of mol of Hcl added = 4.67*0.0772 = 0.36 mmol

pH = 14-(4.75+log((18.95+0.36)/(14.85-0.36))

= 9.12

41)     pkb of NH3 = 4.75

no of mol of NH3 added = 40.09*0.3795 = 15.21 mmol

no of mol of HNO3 added = 40.09*0.3795 = 15.21 mmol

so that , now the system is at equivalence point.

concentration of salt = 15.21/(40.09+40.09)

pH = 7-1/2(pkb+logC)

= 7-1/2(4.75+log0.19)

= 4.98

71) Ksp of BAf2 = S*(2S)^2

Ksp    = 4S^3

(1.84*10^-7) = 4s^3

s = solubility of BaF2 = 3.58*10^-3 M

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