ChemSiddiqui

This type of structures are called skeletal structure. You might like to google how to deduce the MF from these type of structure. Good Luck!

Ok, a bit of fun and also information;

"What's the story behind Schrödinger's Cat?"

Please share!

ecap, thanks for your enormous post.

 

I would like to point out, however, that the question was already answered, and that your post didn't contain any of the information requested by the original post :0)

Exactly what i want to say. It is not as if I am not grateful to him for writing such a lengthy post but I know these stuff already. the only thing i wanted to ask was the magnitude/strength of the forces and I got the help I wanted.

But lets give the person some credit for trying to help out.

thanks a lot hemanntrude. i had been searching/googling it as magnitudes of intermolecular forces but got nothing relevent so thanks!

really appreciate ur help1

Ok i got a question(again)!

What are the forces that hold the molecule together to form a liquid?

Look up examples of the magnitude of these forces and give value in kj/molecule!

Thats the part i am stuck in, how can i possibly know the magnitude or hydrogen bonds, london forces etc.

Can anyone help!

Find the lattice enthalpy of MgF2(s)

 

Mg(s) + F2(g) -------- MgF2(s) -1102 kJmol-1

 

1/2F2(g) -------- F (g) + 79 kJmol-1

 

F(g) + e- -------- F-(g) -348 kJmol-1

 

Mg (s) -------- Mg(g) +150 kJmol-1

 

Mg (s) -------- Mg^2+ (g) + 2e- +2186 kJmol-1

 

 

My calculation is :

 

-1102 + 79*2 + 348 *2 - 150 -2186

and my answer is :- 2584

 

but the modal answer is -2821

 

can anyone please help me thankx

A good idea will be to draw a born cycle before making any calculation. What you do then is that use the forumula:

Enthalpy of formation = sum of all other entalphies(including Lattice enthalphy).

now try to do it yourself and see if the answer comes out right.

hope i have helped

electronegativity is the tendency of an atom to attract shared pair of electron . fluorine has the highest tendency so it is assigned an electonegativity 4 and all other elements has lesser electronegativiy than fluorine . the appropriate scale is one developed by Pauling . and i think the charge dependency of electronegativity is completely wrong .

Hi vedmencum,

Thank you for your answer but like I said i know about electronegativity already its just that i was asking about suggestion about what to write as an answer. Yes, pauling scale is the one mostly used but its empirical , mullikans scale(which takes the average b/w the IE and electron affinity) can give numerical values....except for noble gases.

Thank anyway

ok i am just going to express my views on the post by the OP and because I haven't read through to the last of the thread do forgive me if the discussion is over. I am Muslim and In Quran it is mentioned that any one living in state of non-Muslim will have to abide by the rules of the country given it doesn't in any way interfere with his religion. I live in the UK and a Muslim and I dont find that law here is in any way stopping Muslims to practice their religion and by practicing religon I don't mean 5 times prayers etc, no there is moe to Islam than that, humanity is first always in front of God and any person(Muslim) taking oath by siging any legal document will have to abide by it and try to sort out the problem that are facing the society. But Taking oath from a Quran is optional, if one thinks that he really must not stray from his/her duties and wants to take oath under Quran so that it is in his mind that any wrong doing on his part will be questioned by God(after the involvement of Quran) in my opinion is perfectly ok. I hope the same goes for people of other faiths as well.

sorry sometimes writing length post confuses me so if they are mistakes in the post it simply my bad.

Hi everyone, this is my first post on this forum! I've been stalking it for a little while and now I really need some help. I am a biology major and I am currently taking a relatively basic Chem 112 class. However, my professor moves through lecture very quickly and I'm having trouble understanding the first part on chemical kinetics.

 

Also guys, sorry if I don't provide enough information in this post, i can provide it tomorrow, I've had a long day and i'm making this thread as a last resort before i go to bed. my lecture is tomorrow and i'll be talking to my professor then.

 

Anyways, the part i'm stuck on is first, second, third order reactions. I'm pretty much confused about them in general. Can someone point me in the right direction, to a page that has a general overview or even just explain it to me? I'm also confused about rate law and how it works. I need to be able to learn how they work and then use that information to crunch data from lab reports, or in this case, the problems out of the back of my chem textbook.

yes, i am reading my textbook too but I want to cover all my bases, so thats why I'm making the thread. Thanks guys.

1st order reaction will have a rate equation like;

r = k[X]

2nd order will have the rate equation like

r=k[X][Y] or r=k[X]^2

Order is the power that is raised in the concentration term in a rate equation. If the concentration term(s) have power 1 then the reaction is first order, 2nd if the concentration term(s) have total power of 2.

The equation of the form r=k[X] is usually called the rate equation or rate law.

The thing is that they are many chemical reactions around and it is difficult to characterise all of them according to speed so kinetist(sorry do know the spelling) have come up with way with which the chemical reaction behave. for example the first order reaction could be in plenty amount but any rection that is first order will have rate decreasing exponentially with time. and simliarly for 2nd order the rate will increase with time.

hope that helps somewhat. Good luck!

hi can u help me with this please

 

-which one of these is the atom= 2,8,8,2?

-for neutral atoms with 21-30 protons, the third shell resumes filling;that is, for element 21, the element arrangement is 2,8,9,2.

-a-write down how the electrons are arranged in an atom containing 30 electrons???

-b- how are the electrons arranged in a neutral atom containing 31 protons?

 

thankyou in advance for all ur help. jane (:

The thing that you need to look for in your text book or simply google it is " Electronic Configuration". This is the most common topic among chemistry book where you have to give the electronic configuration or else guess what element or ion has a particular EC.

I will give answer to your first question but forgive me the forums rules don allow me to help you completely unless I or anyother member sees that you have tried to solve the problem and have not merely asked them!.

2,8,8,2 means that there are 2 electron in the first shell followed by 8 in the second and again 8 in the third and then 2 in the fourth and last shell. Remember the valence electron (the no of electrons in the last shell) should direct you to the group from which the element is. For example, in the element has 2 electrons in the final shell so it must be from he 2nd group and adding the number of electron up makes 2+8+8+2 = 20. In a neutral atom, no of electron are similar to no of proton so look in the periodic table and Ca should have this electronic configuration.

Some one asked me this (above)question and thats what i had to say about it;

HF is a molecule in which F is more electronegative than H, that is, F has a higher tendency to attract electron than H, so the cosequence is that this molecule has a dipole, negative over F and positive over H.

B:--> H--------F --------> BH+ + F- (I hope you can imagine the arrows and dipoles over HF molecule)

A nucleophile attach the H dipole and the bond breaks heterolytically so that both electron in the bond go to the same atom in this case to flourine.

I was going fine until here and got stuck as to how to explain further. I will appreciate any comments from you users. I get the feeling i must mention the conjugate base!?

EN depends not only the element but also the ligands and the hybridization

CF3 >> CH3 or CH3< CH2= < CN

and for the same oxydation state

XeF2<XeF+ it depends of the charge

---

Merged post follows:

Consecutive posts merged

EN F 3,8 O 3,5 Cl 3,18 N 3 Br 2,96 the more EN elements

appreciate the reply, but that is not what i am looking for as the answer. I wanted to ask what to write for the answer instead of the dependence of the EN.

But, thanks very much for reply .

well, i only know YT through his threads and replies to my question and I find that he could be ideal choice for president. Needs I say whom i voted for...?

ok we need to develop this, when dealing with nucleophilic aromatic substituion, the electron withdrawing group will infact activate the ring towards the nucleophilic substituion but they still direct the substituent towards the meta position.

is this what you wanted to ask?

i'm not sure if i really know how to figure out an aromatic compound

 

For example, Pyridine

I'm confused about the lone pair electrons on the nitrogen.

Its not on the pi orbital because its on delocalized, right?

That explains why pyridine has 6 pi electrons, all carbons are sp2 and the nitrogen is sp2 as well. Right? lol

 

Another example that im not sure: Oxepin

It has 8pi electrons because only one lone pair electrons on the oxygen is delocalized and not the other?

 

Thank you for the help ^^

Apply "4n+2" or Huckel's rule for planar ringed organic compound. if the number of pi electrons and lone pair agrees with the huckels rule then the compound is aromatic.

ok this is from a past-paper;

Describe the different ways in which the electronegativity of an element has been defined.

I don't know what to answer. I think maybe the question is asking about the pauling, mulliken and allfered-rochow electronegativity values but i can't be sure.

Any help on what the question is asking and what should i write.

Can you speak for all Muslims?

 

Anyway, merry Christmas to you and to everyone using this forum, from me.

I think I can, Muslims are Muslims. Any killing freak or something like that isn't a Mulsim no matter if he calls himself a Muslim. I rest my case. Anyway enjoy Christmas.

Hello all,

From all the Muslims and myself in the world I would like to wish all you, a very happy Christmas and wishes of a wonderful new year!.

Merry Christmas;)!

Hopp in on the peace train!

ChemSiddiqui

the idea about the Cp and Cv for solid has been established but for gases are you guys sayin that when a gas is compressed then we have changed the pressure so the volume is decreased and so does the Cp and vice versa? Sounds logically tough!

And by the way thanks guys .

Hi all,

I read this a while ago and was wondering why the this was so; Cp>Cv for a gas while for solids its the same. I tried to do some research but got absolutely nothing. Any ideas.

Help appreciated.

thnx

I know the peak can't be N2 because N2 doesn't have a dipole hence no absorption peak. The wavenumber matches the co as well as the peak shape so I think my suspicion that there were some traces of CO in the cell.

Thanks for your interest and help though!

No John, I tried the experiment my self and do get some absorption peak. I was quite confused. But now i am thinking that it maybe that the cell i used to put N2 into had been used to put some CO in before so maybe the N2 was mixed with some traces of CO when I put N2 in the cell and it showed some absorption peak

Hi all,

I was just wondering and was infact a bit curious about a question thats was bring put forward to me. In FTIR, N2 is used to take the background right and it is supposed to have no absorption peak becuase it is not a dipole but still the N2 show absorption peak....! I don't know how that can be. May be there is a reason that the in N2 molecule bond if not vibrate but does rotate that show the absorption peak.

I have no clue....any help????!

o i see. I am shit in maths and just don't want to pay attention to some trivial things which i realise can be a disaster but i must get my acts straight in maths.

nomenclature follow a set of rule for organic molecules. Its always important to state where any subtituent will be at the any organic compounds.