AHH! chemistry questions...about GROUP I CATIONS ANALYSIS...precipitate and more..?

Question

please answer the questions you can answer...the most number and correct answer gets 10 points as a reward ^_^

1.) How do you precipitate group I cation such as Pb+2, Ag+1, and Hg+1

2.) What positive application for the presence of silver, mercury and lead?

3.) What is the purpose of centrifuge?

4.) What is the purpose of acidify?

5.)When do you know if your solution is acidic

5.) How do you test for complete precipitation??

Thnx in advance ^_~

Answer 1

1) these ions form insoluble chlorides under acidic conditions. These cations comprise Group 1 are separated from general salt solution by precipitation of their chlorides at pH about zero.
2) Following separation of the chloride precipitate the solide is treated with hot water to dissolve any PbCl2 that is present. The hot solution is mixed with a solution of K2CrO4 : if lead is present a yellow precipitate of PbCrO4 will be produced.
The remaining chloride precipitate is treated with 6M NH3.
If Hg (I) is present a black precipitate containing Hg(s) will form. Any AgCl will dissolve as Ag(NH3)2+.
After separation from the solid the solution is acidified and white AgCl if present will reprecipitates.
3) To 3 mL of your sample in a test tube add 0.5 mL 6M HCl.
Stir well and centriguge.
Decant the liquid and save it for furher analysis
4) In the precipitation as chloride pH must be about zero
5)/6) to make sure that pH is right add 1 drop of 6M HCl to the liquid , Wash the precipitate with 2 mL water and 3 drops of 6M HCl.Stir well. Centrifuge and discard the wash liquid

Answer 2

1) Use H2S

2) +ve application ? You mean use ?

3) To separate materials of different densities.

4) To increase H+ concentration.

5) pH < 7 at 25 deg C

6) Spectroscopically.

Answer 3

ok is placed under Na in the comparable team, That team loses elecrons easily becomeing cations. So ok could be ok+ whilst PO4 could have a detrimental cost. only like that, locate components in the comparable team all of them behave the comparable way.