Ok new rule: you will write an essay and then an abstract to accompany it and if I like your abstract I'll read the essay and consider giving you an avatar.

[QUOTE=Jom;15293332]This sentence is never acceptable... ever. [b][size=300]EVER.[/b][/size]

Everything else is OK with me, though! Congrats.[/QUOTE]

Haha ok :lol:

Thanks :)

is joindate a good reason?

[QUOTE=Permanent Solution;15293257]I think I'm going to implement a policy for myself:
If you post asking for an avatar and you didn't win RMOTM you better write like a paragraph explaining why you deserve it or [B]ima ban yo ***[/B].

^_^[/QUOTE]
[QUOTE=Permanent Solution;15293365]Ok new rule: you will [B]write an essay and then an abstract to accompany it[/B] and if I like your abstract I'll read the essay and consider giving you an avatar.[/QUOTE]

tbqh

[QUOTE]tbqh[/QUOTE]

stfu noob

infract'd

vince, lame. :(

eliminator is the only one allowed to have a big avatar without a reason

[url]http://musicianforums.com/forums/member.php?u=259901[/url]

Advertising spammer?

[color=green]thx[/color]

What happened to the [B]Accent-Competition?[/B]

it was pretty funny and it died. would anyone care, if i would take over the responsibility over this competition? whose idea was it btw.? Rivas?

[QUOTE=repcak;15298691]What happened to the Accent-Competition?

it was pretty funny and it died. would anyone care, if i would take over the responsibility over this competition? [B]whose idea was it btw.? Rivas?[/B][/QUOTE]

Yep. It came out of a long chat one night...like most good ideas.

good, i will wait until he gets online. he's the chief ;)

I didn't follow the first one (wasn't much on line back then I guess) but the concept was smart. I guess Jason won't have problem with kacper running it :)

It was great, hearing everybody's voices. And finding out that Allen and I sound exactly alike.

I submitted an entry but Jason didn't put me in. D=

americans =/= accent

Can someone save me the trouble of writing my essay when I do something good to ask for this avatar and tell me if it's like absurdly too big?

[url]http://s40.photobucket.com/albums/e246/AtreyuUnicorn/?action=view&current=hellraiser2.jpg[/url]

Oh yeah, this was in the Black Metal thread...

[quote]so uhh... who here likes Hinder?

c'mon... I know of few of you aren't as badass as you make yourselves out to be!
I saw you singin' Lips of An Angel while you were in the car![/quote]

That avatar isn't too big, it's just really fugly. Major lol to AtreyuUnicorn.

No essay + abstract = no consideration.

[QUOTE=Cocaine;15301999]That avatar isn't too big, it's just really fugly. Major lol to AtreyuUnicorn.[/QUOTE]

haha yeh, old old oldddddddd account. That was my first sputnik account too fyi.

Ok, I'll write my essay soon as long as it won't be rejected for its size.

Much courage to the man who is going to read Hbp's essay.

If there's no abstract I'm not reading it.

I like the essay idea.

Abstract?

If you don't know what an abstract is, you're automatically out of the running for a new avatar.

[I]abstracttt[/I]

It's true. Inability to use google/wikipedia is inability to get avatars.

I read the essays; Vince gets the abstracts. We have a great system.

I know what the word means, but I'm missing its context in this situation :(

EDIT: Nevermind.

COLOURIMETRIC DETERMINATION OF THE ASSOCIATION CONSTANT OF THE FERRIC-THIOCYANATE COMPLEX ION [FE(SCN)OH2]5]2+


Abstract: Aqueous metal ions can have ligands added through a stepwise addition of H2O. For a given aqueous solution, the association constant may be determined provided only one known co-ordination of the complex is present. Ferric-thiocyanate was analysed colourimetrically, and from this the percentage of the total [SCN] and [Fe] present as complex were calculated. It was found that only 2.09% of the Fe was bound to the SCN, which supports the addition of excess Fe during formation of the complex.


1. Introduction

Metals ions in aqueous solutions are hydrated. Addition of ligands to the metal progresses through a stepwise displacement of the H2O (Housecroft & Sharpe, 2005). The stability, or associative constant, for this process is given by the formula:


where the activity of the aqua ligands is 1 and therefore not part of the expression (Davies & Keene, 2007).

For a given aqueous solution, if only one co-ordination complex of a known formula is present, then the association constant may be determined from the concentration of the uncomplexed metal ions or ligands, or the complexed metal in solution. This may be found through a colourimetric, spectroscopic or spectrophotometric analysis (Housecroft & Sharpe, 2005).

This report aims to determine the association complex for [Fe(SCN)OH2]5]2+ through the colourimetric analysis of a series of solutions. It will then calculate the percentages of total [SCN] and [Fe3+] present as complex in a given solution.


2. Methodology

8 solutions were made up using 100mL volumetric flasks. The solutions were synthesised from ferric nitrate and potassium thiocyanate, with added nitric acid. A detailed method can be found in Chemistry Of The Elements: CH2022 Laboratory Manual, School of Pharmacy And Molecular Sciences, JCU, Townsville, 2007.


3. Results

Table 1: [ ] of Fe3+ and SCN- and Optical Density for each solution
Solution [Fe3+](M) [SCN-](M) Optical Density (470nm)
A 0.024 2x10-4 N/A
B 0.012 2x10-4 0.5143
C 7.2 2x10-4 0.3993
D 4.8x10-3 2x10-4 0.3044
E 3.6x10-3 2x10-4 0.2496
F 3.0x10-3 2x10-4 0.2201
G 2.4x10-3 2x10-4 0.1889
H 0 2x10-4 0

Table 1 shows the results of the colourimetric analysis on solutions A-H. The optical density for A could not be recorded due to experimental error. The Optical Density decreased from B-H. The highest value for Optical Density was 0.5143 and the lowest was 0.

The reciprocal of [Fe3+] in M was plotted against the reciprocal of the optical density in Figure 1 (below). From this, the intercept and gradient was determined.
K = intercept / slope (see practical manual) therefore the association constant of the complex may be determined.



4. Discussion

The plot of the reciprocal of the optical density vs the reciprocal of the concentration of Fe3+ shows a straight line. This line has an intercept of 1.1 and a gradient of 1/95. Therefore, the value of K = 1.1/(1/95) = 104.5. Now, as the value of K is known, it is possible to determine the concentration of the complex [Fe(SCN)]2+ for a given solution. This is due to the formula:
K = [{Fe(SCN)}2+]_
[Fe3+][SCN-]
For solution B, the value of K is 104.5, the value of [Fe3+] is 0.012 and the value of [SCN-] is 2x10-4. Therefore, the concentration of the complex is:



Hence, the % of SCN- present as complex in solution B is 125%. Although the percentage is greater than 100, this can be attributed to human and scientific error within the experiment. The conditions of the experiment, i.e. an excess of iron relative to thiocyanate, indicate that all thiocyanate in the solution would be bound to the Fe3+.

Likewise, the % of Fe3+ present as part of the complex in solution B is 2.09%. Again, the excess of iron relative to thiocyanate supports the low percentage of Fe3+, as the thiocyanate is the limiting reagent.

5. Conclusion

The excess of Fe3+ used in the experiment ensured that only [Fe(SCN)(OH2)5]2+ is present in a relevant amount. Ignoring the aqua ligands, the association constant of the [Fe(SCN]2+ (K) was determined to be 104.5. Therefore the concentration of the complex in solution could be determined, and thus the percentage of total iron and thiocyanate present as complex in solution.




6. References

Davies, M. & Keene, R., Chemistry Of The Elements: CH2022 Laboratory Manual, School of Pharmacy And Molecular Sciences, JCU, Townsville, 2007.

Housecroft, C. E., & Sharpe, A. G., Inorganic Chemistry, 2nd Edition,
Pearson Educational Publishers, Harlow UK, 2005.