RogueRose
International Hazard
Posts: 1594
Registered: 16-6-2014
Member Is Offline
|
|
Question about cation's & anions role in compounds
I had public school chemistry which had abysmal labs (burning a peanut to see how many calories it releases was one of the most advanced labs in
standard 10th gr chem. All further chem knowledge of mine has come from my own curiosity - so please forgive me if some of my questions seem stupid
or obvious.
I'm trying to figure out how different compounds react with each other and whether they will react or exchange parts of the compound.
I have finally figured out how to determine MOLARITY (yes, it was "covered" in public school but not "TAUGHT") and can struggle through stoichiometry
calculations. What I don't understand is how and why some compounds more easily give up say their ammonium groups or sulfates or nitrates over other
compounds I'm thinking that has to do with cation's and anions? If it isn't, what does this have to do with and what are anions and cations?
[Edited on 6-2-2016 by RogueRose]
[Edited on 6-2-2016 by RogueRose]
|
|
|
j_sum1
Administrator
Posts: 6325
Registered: 4-10-2014
Location: At home
Member Is Offline
Mood: Most of the ducks are in a row
|
|
I am not really sure what your question is. I don't know what you mean by "giving up" ammonium groups or nitrates.
Here is a learning pathway:
Learn about ionic bonding, then ionic compounds and properties. After that learn about what happens when ionic compounds dissolve and then about
solubility: including solubility curves. After that learn about precipitation reactions (aka double displacement.)
At the end of all that you will have a pretty good idea on how to isolate ionic compounds. At that stage you will want to watch a few videos on
precipitation reactions, recrystallisation filtering and drying. Follow their example and you will be well on your way to making what you want in the
lab.
In short, find a good textbook (and there is a thread on textbooks for beginners around somewhere.) Read the appropriate sections and the answers to
your questions will pretty much fall out.
|
|
|
PHILOU Zrealone
International Hazard
Posts: 2893
Registered: 20-5-2002
Location: Brussel
Member Is Offline
Mood: Bis-diazo-dinitro-hydroquinonic
|
|
Quote: Originally posted by RogueRose  | I have finally figured out how to determine morality (yes, it was "covered" in public school but not "TAUGHT")
[Edited on 6-2-2016 by RogueRose] |
moLARity has nothing to do with moRALity...at least in the chemical sense  
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
|
|
|
RogueRose
International Hazard
Posts: 1594
Registered: 16-6-2014
Member Is Offline
|
|
Thanks for catching that! Damn auto correct. I had to add molarity to my dictionary so it had changed it to morality without me noticing.
As far as the cation and anion I'm trying to figure out how to determine if reactions work (which are stronger or weaker) by doing something like
mixing a nitrate with a chloride salt or hydroxide buy the compounds don't exchange the nitrate/salt because the cation or anion is too weak. I
apologize for the poor description/explanation and I can't think of an exact example. If you know what I am talking about, is this cation/anion
issues and if so what should I study to help learn this stuff. I guess as an example, I was watching a video on YT about someone making nitric acid
with what I think was calcium nitrate and sulfuric acid but they said adding HCl helped the reaction because of some cation/anion issue. as you can
see, I'm a little confused about this here.
|
|
|
PHILOU Zrealone
International Hazard
Posts: 2893
Registered: 20-5-2002
Location: Brussel
Member Is Offline
Mood: Bis-diazo-dinitro-hydroquinonic
|
|
The answer is multiple...and highly complex...
1°) Enthropy difference, Enthalpy difference and Gibbs free energy difference (all linked to temperature, concentration and pressure) all play on
favored side of reaction, speed of reaction and equilibrium/equilibrii.
2°) Tables of solubility...and solubility constants (Ks) (with help of concentrations and solubility equilibrium/ii) will define if a compound will
be dropped out of solution as a precipitate or not.
3°) Tables of complexations and compexation constants (Kc) (with help of concentration and complexation equilibrium/ii) will define if a compound
will be more prompt to complexate or to remain on its own.
4°) Acidity and basicity tables with help of Ka and Kb will help understand to what side an acido-basic reaction will go.
5°) Also related to equilibrium/ii modification...Lechatelier's principes.
6°) Oxydo-reduction potential tables will reveal if oxydo-reduction reaction may be involved.
Better read and learn (fully understand) chemistry basics before reinventing the Chemistry Wheel...
Trial and error experiments without taking in account the possible product outputs is quite risky...
In your example Ca(NO3)2 is highly soluble, but CaSO4 is less soluble and will precipitate as CaSO4.x H2O (gypsum) while releasing HNO3 (less acidic
and more volatile than H2SO4).
The addition of HCl will cause troubles (and I don't really see its benefit to the original reaction):
-by adding an extra less soluble salt CaCl2 (solubility intermerdiary between Ca(NO3)2 and CaSO4
-HCl is more acidic than HNO3 and than H2SO4 but also much more volatile; also in contact with HNO3 it is involved in an oxydoreduction that destroys
both HCl and HNO3 by forming Cl-N=O (gaseous nitrosyl chloride).
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
|
|
|
DraconicAcid
International Hazard
Posts: 4334
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
| Quote: Originally posted by RogueRose |
As far as the cation and anion I'm trying to figure out how to determine if reactions work (which are stronger or weaker) by doing something like
mixing a nitrate with a chloride salt or hydroxide buy the compounds don't exchange the nitrate/salt because the cation or anion is too weak.
|
Strength/weakness only matters when you are doing acid base chemistry. What you have been talking about seems to be precipitation reactions.
If an ionic compound dissolves in water, the ions really don't pay attention to each other. They're too busy playing with the water molecules. When
you mix solutions containing ionic compounds, if the ions can form an insoluble compound (or a complex ion), they will do so. Otherwise they ignore
each other.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
