Use the information given below to answer questions 8 10. Ag (aq) NH3(aq) Ag(NH3

Question

Use the information given below to answer questions 8 10. Ag (aq) NH3(aq) Ag(NH3) (aq) K 2.1 x 103 Ag(NH3)+ (aq) NH3(aq) Ag(NH3)2 (aq) K- 8.2 x 103 8. What is the equilibrium constant for the reaction: Ag (aq) NH3(aq) Ag(NH3)2 (aq) e. 6.7 x 107 1.7 x 107 b. 1.0 x 104 C. 4.4 x 106 a. 8.2 x 103 9. Which substance is behaving as a Lewis base? e. None of these. b. Ag (NH3) NH3 a. Ag c. Ag(NH3)2+ 10. A saturated solution of silver chloride is in equilibrium with excess solid silver chloride. Which of the following statements correctly describes what will happen when excess ammonia is added to this mixture? a. Additional silver chloride precipitates. b. Ammonium chloride precipitates. c. The silver chloride equilibrium is unaffected by the addition of ammonia. d. The solid silver chloride dissolves. e. The pH of the solution decreases. 11. What is the concentration of silver ion in a saturated solution of AgCl? Aa a. 5.4 x 10-4 M b. 1.3 x 10-5 M c, 1.6 x 10-10 M d. 8.0 x 10-11 M e. None of these 12. A 0.20-mol sample of NaF is added to 1.00 L of 0.35 M Ca(NO302. Which of the following statements is correct? CaF2 precipitates until the solution is saturated. O b. NaNO3 precipitates until the solution is saturated c. The solution is unsaturated and no precipitate forms. d. The solubility of CaF2 is increased by the presence of additional fluoride ions. The presence of NaF raises the solubility of Ca(NO32 13. What is the molar solubility of Cu (OH)2 in a solution buffered at pH 8.50? a. 1.6 x 10-2 M b. 1.8 x 10-7 M c. 1.6 x 10-8 M d. 5.7 x 10-10 M e. None of these

Explanation / Answer

8 . The reaction given just addition of above given reaction so

When we add the reaction then their equilibrium constants are

Multiplied

k of reaction = 2.1 E 3 * 8.2 E 3 = 1.72 E7

So the option d is correct

9 )

We know Lewis base donate lone pair and N has

Lone pair in NH3 so NH3 is lewis base.

10 )
By addition of NH3 , Cl- is removed from the solid AgCl and so solid

AgCl dissolve in the solution.

The option d is correct.

11)

We use ksp value of AgCl

AgCl --- > Ag+ + Cl-

Ksp = [ Ag+ ] [Cl-]

1.6 E-10 = x2

x = [Ag+] = sqrt ( 1.6E-10 )

=1.26 E-5 M

= 1.3 E-5 M

So answer is b ) 1.3E-5 M

12) NaF is limiting reactant so CaF2 precipitate until the solution is saturated

13)

We set up ICE chart

We calculate OH- concentration by using pH

pOH = 14 – pH = 14 – 8.50 = 5.50

[OH-]= antilog ( -pOH )

= Antilog ( -5.50)

= 3.16 E-6 M

    Ca(OH)2   ---- > Ca2+ + 2 OH-

I                                   0              3.16 E-6

C    -x (molar sol.)    +x      +2x

E                                  x       (3.16 E-6 +2x)

Ksp = x ( 3.16E-6 +2x)2

1.6 E-19 = x ( 3.16E-6 +2x)2

Since value of ksp is very small so we neglect x in the denominator

1.6 E-19 = x ( 3.16E-6 )2

1.6 E-19 = x *             1.00E-11

x = 1.60 E-8

Answer : option C = 1.60 E-8 M

           

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