The Periodic Table

CowperKettle

5:43 AM

would "high amines" be an acceptable alternative to "higher amines" (in terms of terminology)?

Freddy

6:16 AM

0

A: Why iron reacts differently with concentrated and dilute sulfuric acid?

Concentrated Sulfuric is very Diamagnetic (-charged) and also very exothermic upon mixing with most other things. Iron is almost the COMPLETE POLAR OPPOSITE (magnetically speaking as it has its own category "Ferro" magnetic or VERY STRONG + CHARGE!) While the dilute sulfuric acid is not as strong...

if anyone wants to edit it

Chemobot

9:39 AM

11

Q: Why is the melting point of p-toluenesulfonic acid monohydrate higher than that of anhydrous p-toluenesulfonic acid?

Why is the melting point of p-toluenesulfonic acid monohydrate higher than that of anhydrous p-toluenesulfonic acid? Compare for example the melting point of benzenesulfonic acid hydrate, which is lower than for anhydrous benzenesulfonic acid.

!!flip

（ノ○Д○）ノ＝＝＝┠

!!gun

】ﾟДﾟ)┳—-ﾟ~:;’:;ω*:;’;—-

CowperKettle

10:01 AM

!!flip\popopo

Chemobot

ミ(ノ￣^￣)ノ!≡≡≡≡≡━┳━☆()￣□￣)/

CowperKettle

!!flip lalala

Chemobot

(/ .□.)\\ ︵╰(゜Д゜)╯︵ /(.□. \)

CowperKettle

!!help

Chemobot

Hi! I'm the almighty bot of ChemistrySE's main chatroom. /!\ If you find me annoying, you can ignore me by clicking on my profile image and chosing "ignore this user" /!\ You can find my documentation here.

CowperKettle

10:03 AM

!!flip/Chemobot

( つ•̀ω•́)つɔɥǝɯoqoʇ

!!wiki/Ленинград

Saint Petersburg (Russian: Санкт-Петербу́рг, tr. Sankt-Peterburg; IPA: [ˈsankt pʲɪtʲɪrˈburk]) is the second largest city in Russia, politically incorporated as a federal subject (a federal city). Situated on the Neva River, at the head of the Gulf of Finland on the Baltic Sea, it was named Saint Petersburg in 1703. In 1914, the name was changed from Saint Petersburg to Petrograd (Russian: Петрогра́д; IPA: [pʲɪtrɐˈgrat]), in 1924 to Leningrad (Russian: Ленингра́д; IPA: [lʲɪnʲɪnˈgrat]), and in 1991 back to Saint Petersburg. Tsar Peter the Great founded Saint Petersburg on May 27 [O.S. 16] 1703. Between...

CowperKettle

!!wiki/Свердловск

Chemobot

en.wikipedia.org/wikiСвердловск

CowperKettle

10:20 AM

Why does sodium form predominantly the peroxide on contact with water?

user116211

10:36 AM

@PhMgBr: o/

PhMgBr

\o

@CowperKettle Hmph?

user116211

The Town Hall Event?

CowperKettle

0

Q: Why does sodium produce predominantly peroxide when burned in air?

From Wikipedia's article on sodium: When burned in dry air, it forms primarily sodium peroxide with some sodium oxide. We know that sodium has a strong reducing capacity, so why does it produce a compound in which the oxygen atom is not reduced to the fullest possible extent?

redox

user116211

Hmm... I just wanted to know what it is all about....

user116211

But during that it ended ;/

PhMgBr

10:39 AM

@MAFIA36790 It didn't. There is going to be next month.

user116211

@PhMgBr What is it about? Is it like Physics Chat Session?

PhMgBr

The linked meta posts explains it better than me.

It's us talking with devs about features all over the network.

user116211

@PhMgBr ooh.

PhMgBr

About how things are, how they should be, how they're meant to be etc.

user116211

@PhMgBr WoW!

Feeds meta.chemistry.se

11:37 AM

0

Q: Do we need a separate tag for phenols?

phenols has just been created by @Jan for this question. My immediate thought was to remove it and replace it with alcohols but I guess we might as well discuss it on meta first. Do we need separate tags for phenols and aliphatic alcohols? Pros: Phenols are notably different from alcohols in ...

discussion tags

CowperKettle

11:48 AM

What oxygen compound is formed depends on temperature, pressure, and the amount of oxygen present — aventurin 1 min ago

Oh, really?

sighs

I wanted to know why.

Maybe because Group 1 elements have big atomir radii combined with small electronegativity?

PhMgBr

2:53 PM

@CowperKettle Well, a lack of oxygens means your ionic compound has oxygens half the number of the metal.

This is something pretty natural. If you're building a wall with x, y and z type bricks, if there are less z, you'll use less z.

Mithoron

o/ @PhMgBr

PhMgBr

@Mithoron \o

How are you doing?

You chat less often @Mith

Lesser than even that time when I said you chat less often. O_o

Mithoron

Haha :)

Why are you worrying?

PhMgBr

I should be worrying.

It's my duty to look after the chatters in this chat.

manshu

!!flip/worry.

Chemobot

3:05 PM

◟(`ﮧ´ ◟ )ʍoɹɹʎ˙

Mithoron

Nah, I'll be ok, but should cut down on procrastination

PhMgBr

And do some real work?!

?!?!?!?

OMG

Mithoron

Terrible, isn't it ?!

manshu

@Mithoron if you do it, then kindly share some tips and your precious experience.

PhMgBr

@MITH IS POSSESSED! @MITH IS POSSESSED! BRING IN THE PRIESTS

Mithoron

3:10 PM

@manshu Dunno, it might be real trauma ;D

manshu

One doesn't simply stop procrastinating.

Mithoron

Indeed

@PhMgBr :D

PhMgBr

I don't like that evil grin

manshu

I am wondering about the time people spend on SE.

@PhMgBr How much do you spend?

PhMgBr

@manshu I am wondering about the time I spend in close vote queue.

@manshu 2-4 hours everyday.

manshu

3:17 PM

I don't have enough privilege to do that now. YAY

PhMgBr

Less if I don't write meta.

manshu

@PhMgBr whoa...that's it?

Mithoron

@PhMgBr Looks you gonna get 2k there!

manshu

I spend hell a lot.

PhMgBr

Nope. 1M users should be able to see who upvoted/downvoted them. — hjpotter92 May 28 '13 at 21:07

2

@Mithoron ᕙ(⇀‸↼‶)ᕗ

CowperKettle

3:18 PM

Should not we multiply the figure by 3, if there are 3 moles?

PhMgBr

Holy shit I am standing in 1973.

The what?

Multiplying what when there are 3 moles where?

CowperKettle

@PhMgBr 2 moles of water, one mole of oxygen

so we should multiply 3 by the 572 kJ/mol-1

PhMgBr

No, why?

CowperKettle

Because the energy is given "per 1 mole"

manshu

@CowperKettle with that logic we should multiply it by 2..

PhMgBr

3:21 PM

This reaction implies you mixed two moles of hydrogen and a mole of oxygen and burned them with extreme prejudice.

manshu

not with 3

CowperKettle

@PhMgBr lol

PhMgBr

The data is provided per mole, because that data is per mole of hydrogen burned.

CowperKettle

> Instead it refers to the quantities of all the substances given in the equation.

"all the substances"

I don't understand that last paragraph

PhMgBr

Well, I don't fully understand that sentence, but this stuff is straightforward math: If one mole of hydrogen burns, you get x kilojoules of energy. If two moles burn, you get 2x.

CowperKettle

3:23 PM

> In this case, 572 kJ of heat is evolved when 2 moles of hydrogen gas react with 1 mole of oxygen gas to form 2 moles of liquid water. (BUT THE 572 FIGURE IS FOR ONE MOLE!)

PhMgBr

Scrolls

CowperKettle

This paragraph is a little confusing, is not it?

PhMgBr

Yep.

I already forgot what I knew.

CowperKettle

I'll write Jim Clark so that he re-writes it clearer.

Because his site is great for beginners.

BBL

PhMgBr

OK OK. Let's rephrase it this way: The standard enthalpies are all reported in kilojoules per mole. Special standard enthalpies are for one mole of the compound. For instance, the standard enthalpy of combustion of hydrogen is -286 kJ/mol.

But delta H r is for the reaction at hand.

Just work with the value given.

CowperKettle

3:27 PM

But is the 572 figure for the whole reaction, or for a mole of something?

PhMgBr

No, it's not for a mole of something.

It's for two moles of H2 burning with a mole of O2.

If it were for one mole of H2 burning with half a mole of O2, it would've been -286.

CowperKettle

So the mol-1 indicator is misleading?

manshu

is it something like "moles of product minus moles of reactants"?

PhMgBr

@manshu Nopes

CowperKettle

Thanks God.

PhMgBr

3:31 PM

@CowperKettle It certainly isn't in enthalpies of combustion, formation etc.

CowperKettle

What?

Stop throwing science words at me! (0:

3

PhMgBr

OK, so the enthalpy of combustion of H2 = The enthalpy of formation of H2O = -286 kJ/mol

They're defined as:

- The enthalpy of the reaction in which one mole of H2 burns.

CowperKettle

Since we've formed 2 moles, it's 572 for the reaction, and the "mol-1" indicator is a gaffe.

PhMgBr

- The enthalpy of the reaction in which one mole of H2O is formed.

But I'm not sure how to interpret mol-1 for that reaction.

That's the gist of the problem.

CowperKettle

nods

Thank you!

manshu

3:33 PM

The standard enthalpy change of formation of a compound is the enthalpy change which occurs when one mole of the compound is formed from its elements under standard conditions, and with everything in its standard state.

CowperKettle

I've got to go..

BBL!

PhMgBr

@manshu Mhm

I ignored the unnecessary details

manshu

The equation shows that 286 kJ of heat energy is given out when 1 mole of liquid water is formed from its elements under standard conditions.

I am copying these things from chemguide + my brain is not working rn.

orthocresol

4:17 PM

@PhMgBr it is just there to make the units work out, if you want a full derivation it is in one of my answers

tl;dr is that the balanced equation does not tell you exactly how many moles are reacting, it only tells you the stoichiometric ratio

hence the necessity to multiply (kJ/mol) by however many number of moles are reacting.

to get a result with units kJ

what i mean is that, that equation unequivocally does not mean that 2 moles of hydrogen react with 1 mole of oxygen to form 2 moles of water.

it means, "per 2 moles of hydrogen reacting with 1 mole of oxygen you get 2 moles of water."

if you were asked to write a balanced equation describing the formation of 1000000 moles of water, you would not write 1000000 H2 + 500000 O2 -> 1000000 H2O, you would still write 2 H2 + O2 -> 2H2O

2

therefore, if the actual reaction you are doing in the lab involves the formation of 1000 moles of water, the gibbs free energy change would be -572 kJ/mol * (1000 mol/2)

PhMgBr

K thanks

CowperKettle

4:44 PM

@orthocresol - you deleted your comments to my question. I hope you'll write an answer. The comments were very interesting.

They really answered the question.

Jan

Hi fellas o/

PhMgBr

\o

CowperKettle

5:17 PM

\\o

PhMgBr

5:30 PM

|o

CowperKettle

0

A: Why does sodium produce predominantly sodium peroxide when burned in air?

Since I will deal with all of the alkali metals in this answer, I think the question should also be broadened. There is no point in covering one single metal (sodium) without touching the others since it is the trend going down the group that we are interested in. So, firstly, some data. There i...

Ya-ay!

The best evening read one can get!

(This side of the Ural mountains)

I wonder what is the meaning of the scalped horisontal eight sign

orthocresol

5:48 PM

proportional to

CowperKettle

@orthocresol Thank you!

The more different ions in a lattice, the stronger it is..

since "v" is in the numerator

$\ce{M_2O_2}$ has v=3. So apparently the double oxygen counts as one ion.

orthocresol

yeah, the peroxide ion is O2(2-), not two of O-.

Peroxide

A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion, O2− 2. The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1. The simplest stable peroxide is hydrogen peroxide. Superoxides, dioxygenyls, ozones and ozonides are considered separately. Peroxide compounds can be roughly classified into organic and inorganic. Whereas the inorganic peroxides have an ionic, salt-like character, the organic peroxides are dominated by the covalent bonds. The oxygen–oxygen chemical...

....

CowperKettle

I remember that face from somewhere

Ah, it's lower down the page (0:

orthocresol

°_°

CowperKettle

Я:°_°:R

ьЪbB

PhMgBr

6:00 PM

@orthocresol This is me when I see a lame joke in chat

CowperKettle

6:13 PM

I wonder what the meaning of "f" and "l" in Hess's cycles' delta-H is (or "what is the meaning"... I forgot how to put it)

Jan

@CowperKettle formation and Lattice, I would say.

CowperKettle

@Jan Thanks!

PhMgBr

Fermentation and lavishness

Jan

fodka and liqour.

PhMgBr

Fluctuation and levitation

1

Q: Vapor-pressure or Vapor-concentration

To summarize from my textbook: rate of evaporation: proportional to surface area but essentially independent from pressure (of surrounding gas) rate of condensation proportional to both surface area and concentration (#molecules/volume) of (appropriate) molecules in the gas At some conce...

physical-chemistry gas-laws phase vapor-pressure

Upvoted just because I saw a first user that can formulate a question

Jan

6:18 PM

@PhMgBr Did that, too.

@ortho, where did you find the values for your lattice enthalpies? I might be able to improve my answer on the stabilities of sulphate and carbonate if I knew where to find them …

CowperKettle

The OP is unregistered

Jan

Searching SciFinder for values like these is tiresome …

PhMgBr

@CowperKettle So?

CowperKettle

@PhMgBr Too bad if his points will be lost for him.

PhMgBr

Won't be, if they merge accounts with a registered one.

Jan

6:21 PM

What Grignard says.

PhMgBr

@Cowp your question just made it to the HNQ. \o/

CowperKettle

@PhMgBr High National Quarters?

PhMgBr

Happy Nomad Quills

CowperKettle

It's Hippie Nomad Quills

PhMgBr

Horse Name Questions

CowperKettle

6:29 PM

Interesting. It takes much energy to form O(2-)

I see. So since alkaline elements are the biggest guys at the Table, for them the denominator in the lattice enthalpy equation is so big that a simple oxide is no so favored.

The superoxide looses out a lot because of its low charge.

Even though when the ion of the superoxide is formed, it is an exothermic process.

Low charge = weak lattice

Low charge also = one metal ion instead of two >> the total charge is low

It's really a superb answer. There are calculations, a reference to another discussion at SE, and take-home points in simple English.

Jan

7:04 PM

Hands up big alkaline guys =3

CowperKettle

(0:

orthocresol

@Jan I wish I knew where to find them. The answer is that they were all taken from my lecture notes

Jan

You have good lectures xD

CowperKettle

Hooray for lecture notes!

Jan

Maybe Atkins is a good source for some things, but … why would one give a table of lattice enthalpies?

I didn't think that was relevant when I had lectures. Nice numbers — forgot 'em O:-)

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