To a 250.0 mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M...

To a 250.0 mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M AgNO3, 0.150M NaBr, and 0.100 M NaCN. The mixture is diluted with deionized water to the mark and shaken vigorously. The Ksp of AgBr is 5.40×10–13 and the Kf of Ag(CN)2– is 1.00×1021. What mass of AgBr would precipitate from this mixture? Do not simply write "0" as some precipitate will form.

Solutions

Expert Solution

Since the complex ion has such a large Kf value (10^21), we assume that essentially all of the Ag+ from AgNO3 is complexed as Ag(CN)2-.

initial mmoles Ag+ (from AgNO3) = M Ag+ x mL Ag+ = (0.0100)(1.00) = 0.0100 mmoles Ag+
initial [Ag+] = 0.0100 mmoles Ag+ / 250 mL = 4.00 x 10^-5 M Ag+

initial mmoles CN- (from AgCN) = M CN- x mL CN- = (0.100)(1.00) = 0.100 mmoles CN-
initial [CN-] = 0.100 mmoles CN- / 250 mL = 4.00 x 10^-4 M CN-

initial mmoles Br- (from NaBr) = M Br- x mL Br- = (0.150)(1.00) = 0.150 mmoles Br-
initial [Br-] = 0.150 mmoles Br- / 250 mL = 6.00 x 10^-4 M Br-

Again, we assume that essentially all of the Ag+ is in the form Ag(CN)2-.

Molarity . . . . .Ag+ . . .+ . . .CN- . . .==> . . .Ag(CN)2-
Initial . . . . . .4 x 10^-5 . . . 4 x 10^-4 . . . . . . . . .0
Change . . . .-4 x 10^-5 . . -4 x 10^-5 . . . . . . .4 x 10^-5
Final . . . . . . . .ca. 0 . . . .3.6 x 10^-4 . . . . . .4 x 10^-5

After the above reaction, how much free Ag+ is in solution to precipitate with Br-? Reverse the Kf reaction to calculate [Ag+].

Kr = 1/Kf = 1 / (1.0 x 10^21) = 1.0 x 10^-21

Molarity . . . .Ag(CN)2- . . .==> . . .Ag+ . . .+ . . .2CN-
Initial . . . . .4 x 10^-5 . . . . . . . . . . .x . . . . . . .3.6 x 10^-4
Change . . . . . .-x . . . . . . . . . . . . . x . . . . . . . . .2x
Equilibrium .4 x 10^-5 - x . . . . . . . . x . . . . . .3.6 x 10^-4 + 2x

Kr = [Ag+][CN-]^2 / [Ag(CN)2-] = ((x)(3.6 x 10^-4 + 2x)^2) / (4 x 10^-5 - x) = 1.0 x 10^-21

Because Kr is so small, the +2x and -x terms above can be neglected, simplifying the expression to

((x)(3.6 x 10^-4)^2) / (4 x 10^-5) = 1.0 x 10^-21
(1.3 x 10^-7 x) / (4 x 10^-5) = 1.0 x 10^-21
1.3 x 10^-7 x = 4 x 10^-26
x = 3.1 x 10^-19 M = [Ag+]

AgBr will precipitate only if Qsp > Ksp.

Qsp = [Ag+][Br-] = (3.1 x 10^-19)(6.0 x 10^-4 M) = 1.86 x 10^-22 which is NOT greater than Ksp (5.4 x 10^-13).

queen_honey_blossom answered 1 year ago

Next > < Previous

Related Solutions

To a 150.0mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M AgNO3,...

To a 150.0mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M AgNO3, 0.225 M NaBr, and 0.100 M NaCN. The mixture is diluted with deionized water to the mark and shaken vigorously. What mass of AgBr would precipitate from this mixture? (Hint: The Ksp of AgBr is 5.4x10-13 and the Kf of Ag(CN)2- is 1.0x1021)

To a 100.0mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M AgNO3,...

To a 100.0mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M AgNO3, 0.190 M NaBr, and 0.100 M NaCN. The mixture is diluted with deionized water to the mark and shaken vigorously. What mass of AgBr would precipitate from this mixture? (Hint: The Ksp of AgBr is 5.4x10-13 and the Kf of Ag(CN)2- is 1.0x1021)

to a 100.0 mL volumetric flask are added 1.00 mL volumes of three solutions: .0100 M...

to a 100.0 mL volumetric flask are added 1.00 mL volumes of three solutions: .0100 M AgNO3, .205 M NaBr, and .100 M NaCN. The mixture is diluted with deionized water to the mark and shaken vigerously. What mass of AgBr would precipitate from this mixture? Hint: The Ksp of AgBr is 5.4 x 10-13 and the Kf of Ag(CN)2- is 1.0 x 10^21

To a 100.0 mL volumetric flask were added 7.00 mL of 1.70 M of H3VO4, 1.401...

To a 100.0 mL volumetric flask were added 7.00 mL of 1.70 M of H3VO4, 1.401 g of NaH2VO4, and 15.00 mL of 1.5 M NaOH. The flask was filled to the calibration mark with water. What were the molar concentrations of H+, OH-, the two other relevant molecules and the pH of the solution? Is the resulting solution a buffer? Ka1 = 1.0 x 10-4, Ka2 = 2.8 x 10-9 and Ka3 = 5.0 x 10-15 for H3VO4.

You have available 1.00 L volumes of the three following solutions: 1.00 M HCl, 1.00 M...

You have available 1.00 L volumes of the three following solutions: 1.00 M HCl, 1.00 M NaOH and 1.00 M NaH2PO4. You wish to prepare 500.0 mL of a buffer solution that maintains a pH of 2.50. Indicate which two of these three solutions you would use to produce this buffer, and calculate the volume of each of these two solution you would need to mix to get the desired volume and pH value for the buffer.

11 mL of 0.0100 M HCl are added to 25.0 mL of a buffer solution that...

11 mL of 0.0100 M HCl are added to 25.0 mL of a buffer solution that is 0.010 M HC2H3O2 and 0.08 M C2H3O2-. What is the pH of the resulting solution?

When 10.0 mL of 1.00 M AgNO3 solution is added to 10.0 mL of 1.00 M...

When 10.0 mL of 1.00 M AgNO3 solution is added to 10.0 mL of 1.00 M NaCl solution at 25.0 ° C in a calorimeter, a white precipitate of AgCl forms and the temperature of the aqueous mixture increases to 32.6 ° C. Assuming that the specific heat of the aqueous mixture is 4.18 J/(g °C), the density of the mixture is 1.00 g/mL, and the calorimeter itself absorbs a negligible amount of heat, what is ΔH in kJ/mol AgCl...

these solutions (2-5) will each be in their own 50 mL volumetric flask. assigned pH for...

these solutions (2-5) will each be in their own 50 mL volumetric flask. assigned pH for buffer system: 4.75 acid/base pair to use: acetic acid and sodium acetate concentration of acetic acid amount of acid to add concentration of sodium acetate amount of base to add unit molarity g or mL (circle one) molarity g or mL (circle one) solution 2 0.05 0.5 solution 3 0.10 0.5 solution 4 0.50 0.05 solution 5 0.50 0.10 Sample calculation for acid (solution...

Ascorbic asic (0.0100 M) was added to 10.0 mL of 0.0200 M Fe3+ at pH =...

Ascorbic asic (0.0100 M) was added to 10.0 mL of 0.0200 M Fe3+ at pH = 0.30, and the potential was monitored with Pt and saturated Ag/AgCl electrodes. Dehydroascorbic acid + 2H+ + 2e- --> ascorbic acid + H2O (Eo = 0.390 V) Using Eo = 0.767 V for the Fe3+/Fe2+ couple, calculate the cell voltage when 5.0, 10.0, and 15.0 mL of ascorbic acid have been added. Correct answers are: 0.570 V, 0.307 V, and 0.184 V but not...

What mass of NH4Cl must be added to 250.0 mL of 0.200 M NH3 solution to...

What mass of NH4Cl must be added to 250.0 mL of 0.200 M NH3 solution to have a buffer solution at pH=8.90? Assume no volume change. A 15.0-mL sample of a H3PO4 solution is titrated with a 1.00 M NaOH solution. The neutralization reaction is complete when 33.6 mL of NaOH is added. What is the concentration of the H3PO4 solution (in M)?

Subjects