ChemSiddiqui

And some more of them:-) :

Here are some more:

Ah.... Beautiful. I always fancy good DNA wallpapers. Thank you and also thanks to your brother for contributing.

One More wallpaper:

Very good darkshade, love the pics. And thank you for the link captainpanic!

As you grow you change some habits but some are there unchanged. I love sleeping. I would slumber on my bed all day if i could help it. But, its how you want it really. I don't like to wake up too early, but at night I am very sleepy to even work but I force myself to work and waking up late at night has been worth it for me really.

Remember its how you like to mould your habits, you dictate them and don't let the opposite happen. Live healthy!

One of the reasons that it's not listed is that these bonds are ion-ion bonds. The reaction involves an electron moving from the Na to the H. This means that not only do you break a bond, and form a bond, you also remove an electron, and add an electron.

 

The half reactions are:

2 Na --> 2 Na+ + 2e-

2H2O + 2e- --> 2OH- + H2

 

The bond energy you're looking for is called "lattice energy", and they are generally not listed in the more common books of chemistry. You'll need a book on inorganic chemistry that focuses on solids. Wikipedia has an article about it: http://en.wikipedia.org/wiki/Lattice_energy, but it's not wiki's best.

 

Hope this was useful.

 

p.s. we're now way beyond the first question as posted by ChemSiddiqui. Guess that's ok. (It's even fun).

Its alright. I am following every single post in this thread and actually gaining a lot.

Please post and contribute Chemistry wallpapers here in this thread:

Bignose I figured it out later that I was doing alright. The solution was right but my substraction wrong (I had put my calculator in a diffrent mode). Thanks any way.

My friend there is nothing else then to suggest you to work hard. Allah in Quran has stated: "What thy will seek is that thy will get". God has promised success if your intentions are pure and you are working exceedingly hard. Do both and leave it to God.

You will become a physician I bet!

Good Luck!

Alright I was doing some statistics questions and I have a probelm. Here goes:

The random variable Z is distributed such that Z

find the probalility:

P(lZl < 1.3) NB. < is actually less than equal to.

My solution:

P( -1.3< Z < 1.3)

P(z<1.3) - [ 1- P( Z < 1.3))

After putting values from the table

0.9032 - (1-0.9032).

0.9032 -0.9068 = -0.0036 (probalility can't be negative so my answer is wrong, mark scheme is saying the answer is 0.8064)

Thanks in advance.

Please help me out on this. I need immediate answers if thats possible. I'll really appreciate any help. This query is from a friend who emailed me:

The experiment was basically to find the percentage purity of three different brands of iron tablets. I did this through titration with potassium permanganate. I also had to do colorimetry with different concentrations of the iron solution and with ammonium thiocyanate (makes solution go red). I also had to do colorimetry changing the thiocyanate concentration and by keeping the iron concentration the same - this would allow me to find the order of reaction. However, i was unable to get these results and so i have had to make them up. I was wondering what the effect of changing the concentrations of thiocyanate and iron would have on the rate - would it double the rate of reaction.

In this experiment iron is present as Fe3+ . i have made up the colorimetry results ( i have roughly made the rate double when the concentration of the chemicals are doubled) - making the overall rate of reaction second order.

I appreciate your help.

Thank you in advance!

For the less common chemicals, it is normal that in literature the heat of combustion is listed. If you need the heat of formation, you have to calculate it from the heat of combustion.

Thank you for your reply. But what you just said was the same thing I asked the reason for?

Potassiun dichromate wouldn't work without any acidic medium. it needs acidity to work. Why does it do so like this I have no idea.. but you can search on the internet. I hope this is what you were looking for!

I think YT is right, because when you look at oxidation states Cu forms then it is +2 which gives a blue ppt and Cu+1 which gives green. CU+2 being more stable. Also hydrogen peroxide is an oxidising agent so I doubt it would have any effect on CuSO4( there isn't any Cu+3 state)!

And you did the right thing by making this sticky YT! good work! and to you too OP!

He asked about intermolecular forces, not intramolecular forces.

OPPS... Sorry I didn't read it properly... !

Hmm... seems interesting!

Ionic and covalent. If we dissociate the said molecule what is formed? NH4+ and OH- . So forces holding the molecule together is ionic while NH4 will be formed from covalent bonding!

I see! Thank you insane_alien!

Hi,

I was pondering over this question and want you people to help me out:

Why couldn’t the enthalphy of formation be found directly but by taking enthalpies of combustion first?

I think it got to do with the time needed to measure the temperature. Any ideas!

take some sample of sea water and try to heat it at home, after sometime you will see when water would have evaporated, some white residue left behind. It is actually the dissolved salts and minerals in sea water which makes it salty!

Yeh Congratulations to every1 who won!

Hi,

I request the moderator to sticky this post.

There is a free software I recently downloaded about sketching formulae of different compounds. I thought I'd share this with others is anyone is interested. You have to register first to download it. Registration is free. Here's the link:

http://acdlabs.com/download/chemsk.html

Good day!

Well, I have decided to add links to all the websites I can find relating to the structure of molecules. Here is this one I found, very useful:

http://www.3dchem.com/

If anyone else also have any links, would they care to add them here as well?!

As per my knowledge it is made of asbestos which is a carcinogen so even purchasing it wouldn't a the most intellegent thing to do. Anyway, I think its banned substance to purchase.

I hope I have helped!