[mishfaksci]

Hi,
I'm new here.
I want a detailed cation analysis practical discussion. Please help me with this.
ABD

[Borek]

Google, read, and come back once you have detailed questions. Nobody is going to do the legwork for you.

Forum rules.

[mishfaksci]

Sorry. I didn't mean to sound lazy earlier.
Why is it preferred to use potassium dichromate than chromate to confirm there is no remaining lead ions?
For identifying lead or silver ions why is KI used, not KCl?
What is the chemical formula of the black residue that indicates the presence of Mercury? And how does it form?
I'd like to understand the above things, please.

[Arkcon]

Sorry. I didn't mean to sound lazy earlier.

That's OK, we don't like having to remid people about the forum rules, but we try to help as best we can.

Why is it preferred to use potassium dichromate than chromate to confirm there is no remaining lead ions?

I have no idea.  That sounds like random trivia, instead of a question that really speaks to this process -- identifying cations.  Looking at their two wikipedia entries, it seems like I'm right.  Both would make chromate anion in solution, lead forms an insoluble chromate, anything you can discover by reading these two pages:

https://en.wikipedia.org/wiki/Potassium_dichromate

https://en.wikipedia.org/wiki/Potassium_chromate

For identifying lead or silver ions why is KI used, not KCl?

What difference is there between the two anions? Something to do with lead or silver?  Something to do with other cations?

What is the chemical formula of the black residue that indicates the presence of Mercury? And how does it form?

What step of the process is that, and what are the reagents used?  And can you try to write a chemical reaction, using those reagents, to give products -- products whose properties match your observations?  That is the task set before you by this question.

I'd like to understand the above things, please.

And presumably, receive credit, for a job well done.  And be able to rely on your logical prowess to solve similar problems.  You've started with good questions, but the search for answers still requires more work on your part than just typing those questions here.

I find myself reminding people more and more -- no one does this in real life.  Anyone who wants to know lead, silver, mercury submits it for ICP-MS, and gets the answer to four decimal places.  The whole purpose to this exercise is to make a flowchart, and apply facts you can find, to determine the plan.  And maybe perform it in class.  But I could write a computer program, using the cations unobtanium, superdopium, and adamatium, with cryptovibraniuc acid, and doomium tetrachloride, come up with some random reactions, and say the sample jumped up and did a dance, and it would be essentially the same class.

[AWK]

In sudent qualitative chemical analysis we use nitrates salts of cations and potassium salts of anions. In discusion very often nitrates and potassium are omitted.

For identifying lead or silver ions why is KI used, not KCl?

.
May be used both. But the former has lower solubility product and is colored.

What is the chemical formula of the black residue that indicates the presence of Mercury? And how does it form?

What reagent did you use? What compound may be formed? What color it shows as precipitate in qualitative chemical analysis? Its toxic properties can be found in "Alice in Wonderland".