Question

1) will silver iodide precipitate from a solution that is 0.0045 M AgNO3 0.15 M NaI, and 0.20 M KCN?

2) Describe how to check a solution for completeness of precipitation

3) A solid is known to be either BaCO3 or CaCO3.It is dissolved in 6 M acetic acid. A pale yellow precipitate forms and k2CrO4 solution is added. the subsequent flame test with that precippitate shows an orange -red color. which cation is present? Briefly explain.

4) what is the electron configuration of Hg+ ion? why does it actually exist as Hg2^2+ ion rather than as Hg+ ion?

Answer 1

2) Suck off a few mls of the clear liquid with a pipette and add to a test tube. Now add a few drops of the precipitating reagent and observe if any cloudiness develops or ptte forms.

1)AgI(s) <=> Ag+ + I-

Keq = [Ag+][I-] = 0.0045*0.15 = 6.75*10^(-4)

Ag(CN) <=> Ag+ + CN-

Keq = [Ag+][CN-] = 0.0045*0.2 = 9*10^(-4)

Keq for AgCN precipitation is much higher than AgI's

Hence, silver iodide doesn't precipitate

3)The color of chemicals is a physical property of chemicals that in most cases comes from the excitation of electrons due to an absorption of energy performed by the chemical. The study of chemical structure by means of energy absorption and release is generally referred to as spectroscopy. All atoms and molecules are capable of absorbing and releasing energy in the form of photons, accompanied by a change of quantum state. The amount of energy absorbed or released is the difference between the energies of the two quantum states. It has all to do with the valence electrons and nothing to do with the other chemicals from the precipitate.

Name Formula Color
Potassium K Lilac/Purple
Sodium Na Yellow
Lithium Li Red
Caesium Cs Blue
Calcium Ca Red/Orange
Strontium Sr Red
Barium Ba Green/Yellow

4)(a) Hg+ electronic configuration:

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s1

(b) In the Hg22+ ion, the two 6s electrons are paired up, resulting in a more stable electronic configuration than a lone Hg+ ion with an unpaired 6s electron.