HELP!!! Qualatative Chemistry

[UNLTuba]

Hopefully there are a few people who have taken chemistry cruising these forums -

I'm working on a qualitative chemistry (seperation of cations) lab. I have a few complex ions that I need to neutralize before I can do confirmatory tests on them in their normal (non-complex ion) states. For example, I have [Zn(OH)4]2- in solution after adding an excess ammount of NaOH to a Zn2+ solution. I want to confirm the presence of zinc by using K4Fe(CN)6, but I first need to neutralize that complex ion I listed above. Do I simply just add an acid (HNO3 for example) to neutralize the basic ion, or is it more complicated than that?

I also have a solution of [Cu(NH3)4]2+ after adding NH3 to solid Cr(OH)3. I need to confirm the presence of chromium again by adding K4Fe(CN)6, but only after I neutralize the basic complex ion solution. Do I do the same thing again and simply add an acid to neutralize it before I confirm it?

Thanks for your help in advance...

 

[LoqT]

I think I had that lab laying around here somewhere.... its been so long since I've done qualitative.... We're finishing up our nucleur chemistry and electrochemistry right now... I hate chemistry.... I HATE IT. I hope organic isn't this crappy.

 

[rgwalt]

Originally posted by: LoqT
I think I had that lab laying around here somewhere.... its been so long since I've done qualitative.... We're finishing up our nucleur chemistry and electrochemistry right now... I hate chemistry.... I HATE IT. I hope organic isn't this crappy.

Dude, you'll either like organic or hate it. Me... I hated it. I loathed that class. It sucked.

As far as the original post goes... I can't be certain, but my inclination would be to add the acid. The H+ (or H3O+) has much more of an affinity for the OH- than the Zn+2 does, so I think the acid would pull those out of the complex and leave you with a solution of Zn(NO3)2. Do you have a lab set you can try this out on before testing your unknown?

Ryan

 

[UNLTuba]

Originally posted by: rgwaltDude, you'll either like organic or hate it. Me... I hated it. I loathed that class. It sucked.

As far as the original post goes... I can't be certain, but my inclination would be to add the acid. The H+ (or H3O+) has much more of an affinity for the OH- than the Zn+2 does, so I think the acid would pull those out of the complex and leave you with a solution of Zn(NO3)2. Do you have a lab set you can try this out on before testing your unknown?

Ryan

I do have a lab where I can test this. However, my group is a little pressed for time as tomorrow is the only day that we have access to the unknown solution. Hopefully I can do some side testing on the specific complex ions that I mentioned while the rest of my group is carrying on the rest of the lab. Thanks for your help! If anyone else has any insight to this, it'd be much appreciated...

 

[NewSc2]

oh god, i'm a chem major and i'm already lost reading your posts. I guess i have to start studying again 🙁

PS - what year are you guys in...

 

[rgwalt]

Originally posted by: NewSc2
oh god, i'm a chem major and i'm already lost reading your posts. I guess i have to start studying again 🙁

PS - what year are you guys in...

I'm a second year grad student in chemical engineering, so it has been over five years since I broke down the basic anion-cation stuff in gen chem. I had to do some qualitative analysis in high school though.

Ryan