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AS Chemistry- helping each other out!

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Okay, my first geniune Chemistry question :teehee:

Question:

The oxygen atom in water has two lone pairs of electrons. Suggest why the ion H₄O²⁺ is not generally formed in acidic solutions that contain H⁺ ions.

Now, I understand that this is related to the effect of lone pairs of Oxygen and that two hydrogens in the ion form dative covalent bonds with the Oxygen and the other two hydrogen atoms in the ion form normal covalent bonds with Oxygen but I don't know to link that into the the question

Does it have anything related to the change of the shape of the ion and therefore the knock-on effect of becoming a non-polar molecule?

Can someone explain?

Thank you :colondollar:

(edited 9 years ago)

Reply 701

Dylann

Original post by zhang-liao

Okay, my first geniune Chemistry question :teehee:

Question:

Now, I understand that this is related to the effect of lone pairs of Oxygen and that two hydrogens in the ion form dative covalent bonds with the Oxygen and the other two hydrogen atoms in the ion form normal covalent bonds with Oxygen but I don't know to link that into the the question

Does it have anything related to the change of the shape of the ion and therefore the knock-on effect of becoming a non-polar molecule?

Can someone explain?

Thank you :colondollar:

Interesting question...probably because if there are H+ ions floating about they are likely to be attacked by water rather than by H3O+ ions. Also, H3O+ is a postive ion, and joining together two positive ions (h+ and h3o+) may cause some repulsion and thus be very unstable when actually formed (and thus split back into h3o+ and h+ ions)

Reply 702

Feraligatr

Original post by Dylann

Yeah but would there be any relation to intermolecular bonding though?

Quite a strange question to ask though :colondollar:

(edited 9 years ago)

Reply 703

louisaerin

Which is more stable cyclohexane or benzene?

Reply 704

Dylann

Original post by zhang-liao

Yeah but would there be any relation to intermolecular bonding though?

Quite a strange question to ask though :colondollar:

Well I would assume all the bonds in H4O2+ would be covalent, or at least dative covalent, and not to with intermolecular forces. But it's a good question and I'll ask a teacher or someone (you should do, and compare answers)

Original post by louisaerin

Which is more stable cyclohexane or benzene?

Benzene because the delocalised ring structure is very stable. You sure this is AS?

Reply 705

louisaerin

Original post by Dylann

Thank you I am doing AS chemistry and this question was on my assignment this week

Reply 706

hakunapinata

Original post by Gott

I'm doing OCR AS

How many assessed practicals have people done, I've done 1 qual 1 quant?

hey I've done one eval one quant

Reply 707

kira1

Original post by noshahmad

I am doing OCR salter chemistry and would be more than happy to help granted I've learnt the content myself :smile:

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Would you be able to help me if I ask you a few questions ?

Reply 708

cerlohee

Original post by Dylann

H+ doesn't exist only the hydroxonium ion though? And there's an additional oxygen in the molecule posted before? As in h4o2 not h4o

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Reply 709

Dylann

Original post by cerlohee

H+ doesn't exist only the hydroxonium ion though? And there's an additional oxygen in the molecule posted before? As in h4o2 not h4o

Posted from TSR Mobile

I think the 2 was the charge, so it's basically a water molecule with 2 extra hydrogens. H4O2+. And you're right, the H+ floating about (from the acid) will be attacked by water instantly, so h3o+ will form. But I think it's unlikely the h3o+ will attack h+ due to replusion and instability

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Reply 710

l1lvink

Original post by louisaerin

Which is more stable cyclohexane or benzene?

Thermodynamically, cyclohexane is more stable than benzene.

Reply 711

Dylann

Original post by l1lvink

Thermodynamically, cyclohexane is more stable than benzene.

Why?

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Reply 712

l1lvink

Original post by Dylann

Why?

Posted from TSR Mobile

I'm going to admit that I didn't know the answer, so I looked it up. This appears to be the answer:

All six carbon atoms in benzene are sp2 hybridized. The two sp2 hybrid orbitals of each carbon atom overlap with the sp2 hybrid orbitals of adjacent carbon atoms to form six sigma bonds in the hexagonal plane. The remaining sp2 hybrid orbital on each carbon atom overlaps with the s-orbital of hydrogen to form six sigma C–H bonds. The remaining unhybridized p-orbital of carbon atoms has the possibility of forming threeC bonds by the lateral overlapping.
The six π’s are delocalized and can move freely about the six carbon nuclei. Even after the presence of three double bonds, these delocalized π-electrons stabilize benzene.[ π cloud] about cyclohexene and cyclohexane both are more saturated than benzene but they have specific structures and can only be present in that form only but for benzene it not only has the extensive π cloud but also resonating structures so it can remain in any one of those structures so it is more stable in terms of entropy..Not only benzene but also many other substances show these properties they are broadly classified as AROMATIC COMPOUNDS..

Reply 713

bellabella136

Heya so I have a quant isa on Tue on observations and balanced symbol equations. Any help? Im crap at isas :tongue:

Reply 714

Dylann

Original post by l1lvink

Yeah that makes sense. I think if you compare the thermodynamic properties as you said, it could suggest cyclohexane is more stable, since cyclohexane has a enthalpy of formation of about -170 and benzene has +50. Though this doesn't necessarily indicate stability as the part you quoted talks about overlapping of orbitals which is actually more to do with stability than enthalpies.