Chemistry Question

Post by **KingManULTRA** » Mon Apr 03, 2006 11:25 pm

Why is magnesium hydroxide, with formula Mg(OH)2, not known as magnesium dihydroxide?

Post by **tnf** » Mon Apr 03, 2006 11:33 pm

because when naming binary ionic compounds you don't use prefixes.

prefixes generally are found on covalent compounds.

i.e. carbon dioxide (covalent bonds)
vs calcium oxide (ionic bond)

Post by **tnf** » Mon Apr 03, 2006 11:34 pm

Which reminds me - I got selected to teach AP Chemistry next year. yay (this will eliminate the 2 freshman classes I was teaching).

Post by **KingManULTRA** » Mon Apr 03, 2006 11:34 pm

Okay...it still seems like it would work though. I guess it's just a Chemistry law.

Post by **Wizard .3** » Mon Apr 03, 2006 11:37 pm

dont't question the universe.

Post by **tnf** » Mon Apr 03, 2006 11:37 pm

It's not about working. Its because you don't need the prefixes because knowing the charges of the ions lets you know what the subscripts in the formula woudl be anyhow.

In covalent compounds, you need the prefixes though because there aren't fixed 'charges' you are dealing with.

Post by **menkent** » Mon Apr 03, 2006 11:38 pm

yea, if you know the charges of the ions it's already evident that there will be two hydroxide ions. Mg is +2, so it will always hook up with two OH-.
so, to answer your question: redundancy avoidance.

Post by **tnf** » Mon Apr 03, 2006 11:39 pm

menkent wrote:yea, if you know the charges of the ions it's already evident that there will be two hydroxide ions. Mg is +2, so it will always hook up with two OH-.
so, to answer your question: redundancy avoidance.

Yes, redundancy is probably the best way to put it.

Post by **menkent** » Tue Apr 04, 2006 2:06 am

somewhat like me posting an already-posted answer to his question

Post by **Chupacabra** » Tue Apr 04, 2006 2:38 am

KingManULTRA wrote:Why is magnesium hydroxide, with formula Mg(OH)2, not known as magnesium dihydroxide?

its because its already implied in the name

Post by **l0g1c** » Tue Apr 04, 2006 2:47 am

Chupacabra wrote:
KingManULTRA wrote:Why is magnesium hydroxide, with formula Mg(OH)2, not known as magnesium dihydroxide?
its because its already implied in the name

and being as such, would be redundant :icon11: :icon10:

Post by **Chupacabra** » Wed Apr 05, 2006 5:14 am

l0g1c wrote:
Chupacabra wrote:
KingManULTRA wrote:Why is magnesium hydroxide, with formula Mg(OH)2, not known as magnesium dihydroxide?
its because its already implied in the name
and being as such, would be redundant :icon11: :icon10:

yeah, i know