problem 1: A sample of aqueous 0.1 M cobalt (II) nitrate was prepared.

a) What is the ligand in this system? What is the structure of the complex?
b) What is the hybridization of the cobalt ion?
c) How many bonding molecular orbital are occupied? How many are non-bonding? How many are anti-bonding?

problem 2: In the synthesis of hexaamminenickel(II) chloride, concentrated 15 M aqueous ammonia is added up to an aqueous solution of nickel(II) chloride. The sample is washed with small portions of ether and is stored in a closed vessel.

a) Compare the color of the aqueous solution before and after the addition of the ammonia.
b) Predict the number of unpaired electrons in the product.
c) How many bonding, non-bonding, and anti-bonding molecular orbital are occupied in the product?
d) Why is concentrated ammonia used instead of dilute ammonia? What would occur to a sample of the complex left in an open bottle?

problem 3: Anhydrous solid manganese (III) chloride is extremely dark violet while the solid tetrahydrate, MnCl₂•4H₂O, is light red.

a) Give a description for the striking changes that take place when the anhydrous salt is hydrated to form the tetrahydrate.
b) What changes will take place when the anhydrous salt is exposed to vapors of ammonia?

problem 4: A recent paper showed that liquid water is a mixture of high density and low density forms.

a) Propose a structural basis for the difference in density observed for the two forms.

b) Propose why the fraction of the low density form reduces as the temperature increases.

c) Oxygen-hydrogen stretching bands in the infrared spectrum at 3120 cm^-1 and 3540 cm^-1 were assigned to the two forms. Which band belongs to which form?