Chemistry 4A Supplemental Problems Solubility and Complex Ions 1. Which insolubl

Question

Chemistry 4A Supplemental Problems Solubility and Complex Ions 1. Which insoluble compound of each pair should be more soluble in nitric acid than in pure water? a) PbCl2 or PbS b) Ag COs or Agl c)A(OH)s or AgCl 2. Which of the following barium salts should dissolve in a strong acid such as HC? Ba(OH2 BaSO4 BaCOs 3. A solution is prepared initially containing 0.050 M Po(NOsh and 0.20 M NaF. What will be the concentration of all ions after precipitation of PbF2 occurs? 4. A solution is made which is initially 0.10 M in Cd.2 and 1.0 M in NHs. This causes the [Cd(NHs)J 2 complex ion to form, as shown in the equation below. Determine the concentration of free Cd+2 ion in this solution. 5. Compare the solubility of AgBr in water with its solubility in 0.50 M NHs solution. 6. A0.010 M solution of AgNOs is made 0.50 M in NHs, thus forming the [Ag(NHshl complex ion. Will AgCl precipitate if enough NaCl is added to make the solution 0.010 Mina? N-01 x 0 _ [z.qd] A 0ro = [-d] N oro-I-ON] N oro [.EN] (E

Explanation / Answer

1. solubility of salts in HNO3

a. PbS forms H2S from soluble S^2- ions in solution in HNO3 which is a weak acid and dissociates only to a small extent, thereby increasing solubility of PbS.

PbCl2 forms HCl a strong acid which dissociates completely into ions and hence no change in solubility.

b. Again H2CO3 formed in Ag2CO3 is a weak acid, and thus Ag2CO3 solubility increases in HNO3

HI is a strong acid (formed from AgI).

c. Al(OH)3 solubility increases in HNO3 as it forms Al(OH)4- soluble species

2. Barium salts dissolves in HCl,

BaCO3 : as it forms H2CO3 a weak acid

BaCO3(s) <==> Ba2+(aq) + CO3^2-(aq)

reduces CO3^2- on right hand side and thus more BaCO3 dissolves to maintain this CO3^2- concentration in solution at equilibrium.

3. 0.05 M Pb2+ with 0.20 M F-

PbF2 = 0.05 M

concentration of [Pb2+] = 0 M ; [NO3-] = 0.10 M ; [F-] = 0.10 M ; [Na+] = 0.20 M after precipitation of PbF2

4,5,6 - Formation constant needed

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