Homework # 4 Key ; Due 9/17/01

Homework # 5 Key ; due 9/24/01

Chapter 8.

68.  I-

I- 

I-  has only lone pairs – Lewis Base

b. H2O always Lewis base

c. CN- has lone pairs – Lewis Base

72. Oxide donor is the base.

b. CaO is an oxide donor – base

SiO2 accepts oxide in step 1 and 2. It is acid so other is base.

CaO still oxide donor; Ca2SiO4 must be acid

Chapter 9

4. MgSO4 MW = 120.3 g 1/120.3= 8.31 x 10-3 moles

1.898 –1.0 = 0.898 g H2O = 0.0499 moles H2O

1.150 –1.0 = 0.150 g H2O = 8.33 x 10-3 moles

8.31 x 10-3/8.33 x10-3 = 1 water

0.0499/8.31 x 10-3 = 6.00 = 6 water

6. 255 AgNO3 255/169.9 = 1.50 mol 1.50 mol/100g H2O = 15.0 mol/1 kg H2O

This is the solubility at 30oC.

12. Ag2SO4(s)+ H2O 2 Ag+(aq) + SO42-(aq)

Ksp = [Ag+]2[SO42-]

Cu(OH)2(s) Cu2+(aq) + 2 OH-(aq)

Ksp = [Cu2+][ OH-]2

Br2(l) Br2(aq)

Ksp = [Br2]

CaF2(s) Ca2+(aq) + 2 F-(aq)

Ksp = [Ca2+][ F-]2

16. Ksp = 1.1 x 10-10 for BaSO4

Ksp = [Ba2+][SO42-]

x2 = 1.1 x10-10 ; x = 1.0 x 10-5

22. .00896 g Pb(IO3)2 ; .00896/557 = 1.61 x 10-5 Moles/0.4 L = 4.02 x10-5 M soln

x = [Pb2+] = 4.02 x 10-5 ; 2x = IO3- = 8.04 x 10-5

Ksp = (4.02 x 10-5)(8.04 x 10-5)2 = 2.6 x 10-13

26. 0.09 g PbI2 = 0.09 g/461 g = 1.95 x 10-4 mol/1 L = 1.95 x 10-4 M

Q = (1.95 x 10-4)(3.90 x 10-4)2 = 2.97 x 10-11 < Ksp no ppt.

30. 140 mL 0.001 M = 1.4 x 10-4 moles Sr2+/ 1L = 1.4 x 10-4 M soln Sr2+

0.005 M Na2CrO4 x 0.86 L = 4.3 x 10-3 moles CrO42-/1L = 4.3 x 10-3 M CrO42-

Q = [Sr2+][CrO42-] = (1.4 x 10-4) (4.3 x 10-3) = 6.0 x 10-7 < 3.6 x 10-5 ; no ppt.