@Secret I would guess the answer is no; say one molecule of the compound has X molecules of water of crystallization; then, the extra volume due to those X H2O is = X * (18/NA) cm^3 which is extremely insignificant unless X is at least of the order 10^15, which rarely happens anyway
Raoult’s Law become a special case of Henry’s Law when K=P⁰ , but where do these laws differ from each other?
There’s a statement in my text book which I’m having trouble understanding.
The statement:
As a real solution approaches the limit of infinite dilution its components behave more id...
Regarding the first molecule: I understand that the simplistic Fishcher projection - with all its bond depicted by solid lines - can be very confusing at first glance in determining optical activity. You may believe it to be optically inactive, hoping for a center of symmetry to exist, but it is ...
mind having a look at why my wedge bonds are not smooth?
first time user here I wonder if you've seen something similar before. thanks ^_^
@GaurangTandon [Re: Why does nitrogen have a maximum covalency of 4?] The general problem with covalency is, that there is no good and unambiguous, or even official definition of it. Some use the number of shared electron pairs, some use the number of covalently bound substituents (although how would you tell what is covalently bound?), and there are probably more uses out there.
Valency is not the same as covavalency, but it suffers from the same fuzzy definition problem...
The IUPAC defines it as the number of univalent atoms. That makes it a fixed number: Nitrogen 3, carbon 4, halogens 7, Xe 8, He 0, etc... Greenwood waters the definition down to binary hydride or twice the number of oxygen atoms in its oxide(s). This means it can have more than one value. Which one do you take? Which one is correct? It depends.
More rigorous is coordination number. It is something you can actually count, and it only depends on the compound you are looking at. Therefore hypercoordinate compounds have a cn higher than usually expected. Besides that valency and related concepts are not useful, they actually don't tell you anything. Maybe they may help you classify what is "normal" or "boring", but when it comes to actual chemistry, it doesn't tell you anything.
I understand that for some fundamental, basic beginners course, these simple concepts can be helpful at getting a grip. However, it really is necessary to teach from the beginning, that there are limitations to this point of view, and maybe hint at the deeper going stuff. It really is hard to fight these common misconceptions, because some teachers don't know better, and some students only trust what their teacher says.
The d-orbital contribution and octet-expansion are such problems, and I am not yet prepared to give up the fight.
@Martin-マーチン I agree with that. I myself searched for the definition of covalency before posting the answer, but I couldn't find anything conclusive
@Martin-マーチン "when it comes to actual chemistry, it doesn't tell you anything." Yes, I agree with that also. I myself am more used to the oxidation state (is it more/less useful than coordination number?), that's the first thing I commented on the question of the OP as well, but later figured out he was asking for the covalency instead
@Martin-マーチン come to my region high schools once, you'll be amazed at the quality of the high school chemistry textbooks (spoiler: they're terrible :P). I myself am grateful to the quality answers out on Chem.SE otherwise I would have never learnt any chemistry at all
the fact is that the OP asked a simple question, and I followed up with a simple answer, which I knew from high school (and truth be told I wasn't prepared for the sudden avalanche of upvotes :P)
so, what do you think I should do? edit the answer to include all the details you mentioned?
oxidation state is quite well defined, but there are also a few problems. usually it is safe to use. Know what you're doing and everything will be swell. For example, you need to know the structure (and coordination number) to assign oxidation numbers in N2O5... Problematic are cases like Fe3O4... and fractional on in general ;)
@GaurangTandon Well I found that initial one quite compelling, that's when I edited it and voted on it chemistry.stackexchange.com/revisions/90576/3 Maybe add that you define covalency as number of shared electron pairs to make that point clearer, but nothing more was asked and the hypercoordination stuff will probably just confuse op
@GaurangTandon It certainly is better, but has phosphorous really covalency 5 in PCl5? There are only 8 shared electrons. The bonds itself have high ionic character (at least more than in PCl3), so is it really correct assigning a covalency in this case? In the first case -- using covalency = no of shared electron pairs -- the covalency would still be 4.
And i would say that the coordination number is an older concept than valency/covalency
@Martin-マーチン "There are only 8 shared electrons" whoa, then how come there are five sigma bonds with chlorine? is that because of this 4c-3e thingy? chemistry.stackexchange.com/a/18544/5026
@GaurangTandon yes and no. What ron presented there is an approximation, too, but it will help you understand why there are only 4 ep shared, the non-bonding orbitals don't contribute to that.
in a MO set-up you'd get the same conclusions from symmetry adapted ligand orbitals.
basically you have one totally bonding orbital s of P with ligand lone pairs, two degenerate orbitals using the equatorial ligands, and one orbital using the axial ligands; and of course the anti-bonding combinations
@GaurangTandon They aren't bad . That's just something everybody going to coaching centres keeps on repeating . I don't know why, Nearly all the jee toppers say that NCERT is a must.
@AvatarShiny I personally dislike NCERT; though it's preface mentions the top professors wrote it, I still find it lacking minute details that are useful for JEE, and the presentation of the content is bleak
@Loong welcome :) i wonder quite a lot of users refer to the NCERT here
Oh, and while we're at it, do note that there's a difference between NCERT and NCERT Exemplar books.
I used this non-official source for NCERT exemplar tiwariacademy.com
tl;dr: NCERT = main syllabus book prescribed for all students; has theory+review exercises; NCERT exemplar = supplementary book containing slightly tougher problems, no theory
@AvatarShiny well yeah I knew biology had alot of mistakes and I really hate that even NCERT says that glass flows..but is there anything else gravely wrong?
@Martin-マーチン Although NCERT has many mistakes, most of the examinations in India are based on it. So, students have no choice but to learn and 'memorize' NCERT. And most of the students have no interest in obtaining correct information but only score high.
A question for inorganic/metallurgy experts: Why don't people use systematic nomenclature as used in organic chemistry for names of ores? My book has names of more than 40 names and I'm expected to learn them. Why not use IUPAC nomenclature so that one does not need to memorize every name but just a handful of rules?
@ApoorvPotnis so you're saying why experts in a field don't use a convention experts in another field use? Well, I'm afraid the answer would be they just don't.