Post by: WhoTookMyUsername on August 22, 2011, 07:37:25 pm
How can i tell what state compounds are naturally found in?
Are there any rules to help?
My teacher said all acids are (aq) but acetic acid etc. isn't?
thanks (yes i am noob at chem, been focusing on the bio :D)
Post by: Tashi on August 22, 2011, 08:12:54 pm
Post by: REBORN on August 22, 2011, 09:33:00 pm
Post by: pi on August 22, 2011, 09:41:36 pm
Pretty sure acetate acid is aq
It's acetic acid. :P
And in fact you are both correct, and incorrect. It can be either a liquid (normally called glacial acetic acid, i think) or diluted as an aqueous solution :)
Post by: WhoTookMyUsername on August 30, 2011, 08:07:47 pm
How can you determine the extent to which an acid / base dissociates in water? ( strength of acid ) without specific figures ( e.g. When it says, list following according to electrical conductivity)?
2) why is nano3 neutral when na3po4 is not?
I know na 3 po4 dissociates, then po4 accepts hydrogen atoms like bases do, but why is it not the same with nano3?
3) in the acid base reacitn between ammonia and hydrogen chloride, do you leave ammonium and chloride ions separate or do they become ammonium choride and why?
Tanks
Post by: Mao on August 30, 2011, 09:44:31 pm
Strong acids = complete dissociation = HCl, H2SO4, HNO3
Moderately strong polyprotic acid = H3PO4
Weak acids = CH3COOH, almost everything else
2) The conjugate of NO3- is HNO3, a strong acid. When a strong acid reacts, it is because it is extremely favourable for it to dissociate, like going downhill with a sharp slope. For it to go backwards, you need to go against the original reaction (i.e. going uphills with a sharp slope), which is very hard. Therefore it doesn't happen (or only does so at a negligible rate). This is why NaNO3 is neutral.
3) In solution, they are dissolved ions, and thus are separated from each other. Though for simplicity, you could write
Post by: WhoTookMyUsername on August 31, 2011, 01:12:40 pm
just as an extension on question (2)
is another way of looking at it to say Nitrate (compounds of) is highly soluble but phosphate not?
So HNO3 would dissociate removing its 'basic' effect, whereas H3PO4 would not?
Does this apply for all the ions in the solubility chart
?
Thanks
Post by: Mao on September 01, 2011, 01:27:48 am
just as an extension on question (2)
is another way of looking at it to say Nitrate (compounds of) is highly soluble but phosphate not?
(this response is mostly speculations, and most of it will be above the VCE level, but here it is anyways)
I don't think acidity can be solely explained with solubility. I am not sure what the relative solubilities of HNO3 and NO3- are, and so I cannot make a good judgement of if solubility play a role in deprotonation (acid donating a proton). I do know that this process can be highly exothermic, and the chemical energy released far outweighs any free energy change from dissolution, so it is unlikely solubility plays an important role. This does not mean it can be completely neglected though, it is plausible that for some molecules this contribution is relatively important. Another point to consider is that water has a harder time dissolving ions with higher charge density, so a multiply-charged ion such as the phosphate ion would have a strong ionizing effect on neighbouring water molecules, essentially ripping H+ from nearby waters due to its large negative charge.
The science of dissolution is not well understood yet. For now, probably best to treat ionization of acids/bases and dissolution separately. Maybe one day a theory will be developed to relate solubility with other phenomena in water chemistry.
Post by: WhoTookMyUsername on September 01, 2011, 07:06:33 am
yeah in this case compounds of No3 are highly soluble, whereas compounds of Phosphate are not (excluding a few, but INcluding H3PO4)
Post by: Mao on September 01, 2011, 12:36:09 pm
okay thanks mao -
yeah in this case compounds of No3 are highly soluble, whereas compounds of Phosphate are not (excluding a few, but INcluding H3PO4)
In my opinion, solubility is not a good way to look at relative basicity.