Kaeroll

You need to provide more information. I assume by ether you mean diethyl, but which reactions did you have in mind? I feel a complete rundown of ether reactivity is beyond the scope of this forum. Kaeroll

If you want to take a peek at a more accurate picture, google Molecular Orbital theory.

Since it's already been bumped without an answer I feel it's worth providing some advice. Apologies if anyone feels this is necromancy, heh. 1. What is a rate? It is how fast a quantity changes with time. You can get this from a straight-line graph as a gradient. 2. The OP answered their own question here. 3. Also answered. If the rate were dependant upon , the rate would vary with (I realise that's stating the obvious...). As it doesn't, the rate must be independant of . 4. To eyeball it, if the rate of reaction is independant of a reaction, it can have only one possible order. Think about it. A more thorough way to investigate this is to repeat the experiment with varying initial , holding all else constant, and see what effect it has on rate. 5. Once the answer to #4 is found, this will become evident. If the rate is not influenced by , is it involved in the aptly-named rate-determining step? 6. Where is the intercept found? (t=0). What should equal at this point? (It's a known quantity calculated from the protocol) 7. There's probably several ways to work this out. Personally I'd extrapolate back to initial to determine what volume would be required. As initial is known, the extrapolated volume can be used to determine [thiosulphate]. For bonus points, consider what the rate-determining step of the reaction might be. Spoiler: the OP was right, is not involved in the RDS. To work this out try to draw out a mechanism for the reaction. Three steps are required. I plotted the OP's data in Excel and wasn't too impressed- the data does seem to curve somewhat but this is likely down to error more than anything else. More points would probably have been nice. (for some reason in this post, is coming out in lower case. Anyone know why?) Kaeroll

Ferrero Rocher all the way. Never seen what all the fuss is about Lindt.

Hr, interesting actually. I've only ever caught small parts of the Daily Show (usually the hilarious parts) so it's different to see Stewart being slightly more serious. To be fair, less than a minute into the second clip he points out that they're both "snake-oil salesmen" but that the Daily Show is clearly labelled as such. Kaeroll

If won't break your Krebs cycle. It probably won't do anything. Bear in mind that the cycle is central to your survival, so is pretty damn efficient. Do you really think it needs supplements? Spend your money on something more useful and worthwhile (I recommend Rock Band... oh the fun...)

edit- think I missed the point here. Disregard this.

Personally this was (to an extent) the message I took from the book all along. I always found it compelling that only one (arguably three) people completely stick to their morality at the end. Veidt finds what he does repulsive - he doesn't want to kill innocents but feels he has to. It's really telling when he asks Manhatten if it worked out ok "in the end". Nite Owl and Silk Spectre both fall in line with his plan shockingly quickly in the book - agree first, ask questions later (in the film they take longer over it. A friend of mine complained about Nite Owl attacking Veidt in the film, but I thought it was a better response than the book version). They all go against their high-handed morality. Rorschach is the only one who refuses to compromise and sticks to his guns, no matter what. The Comedian and Manhatten are less clear - can Manhatten be said to have morality at all? I was never quite sure what to make of the Comedian's breakdown to Moloch so I leave that with a big question mark beside it. Of course, the beauty of the ending is that we're all more inclined to identify with Nite Owl/Silk Spectre, taking the path of least resistance (and damage). Both the film and the book are great in not passing judgement at any point- we are left to figure out the meaning of the ending, and question whether it's right to be moral.

Cheers for the replies. My first port of call was the Wiki article, and while it has plenty of information about how it can occur and what's so nasty about it, it doesn't say how it can hang around afterwards, even if the offending (bulk) material is cleaned up. So I guess your suggestion is that trace amounts left over are responsible, gdg? (FWIW - I'm also a chemist, in training..) W/r/t Po in particular - yikes!

Not sure if this belongs in chemistry or physics, but I figured it'd get more exposure here. In brief, my question is: what is the mechanism of radioactive contamination? Bit of context to what I mean, at a university in the UK there has recently been a controversy over the use of what was formerly Ernest Rutherford's lab. Several people working in the building have recently died from cancer, and there's fear it's still contaminated from his work. I'm familiar on a basic level with radioactivity, but it's not my specialty at all. How can radiation linger for nearly a century? My guess would be that nuclei in (for example) the walls, floor, etc. are converted to radioactive nuclides with longer half-lives. Anyone care to fill me in?

I think it's a matter of intent. If you genuinely wish to discuss and develop your speculations, and consider how they could stand or fall by empirical evidence, I reckon you'd be ok. They seem a nice enough bunch round here. You can hardly be faulted for saying, "I have this idea, based on x y and z, though I've no proof. What do you guys think?" I think the approach that'll get you b-tchslapped or ignored by everyone who reads your thread is "I have this idea. It's right. Live with it, and maybe chuck a Nobel prize my way." Just my two pence, I'm not a regular participant in this board really.

I loved every second of it. I can see why people would dislike it, especially those unfamiliar with the comic. There seems to be a distinct lack of exposition in places. But I sat through it grinning from ear to ear; the casting was spot on (particularly Rorschach and the Comedian) and the minor changes to plot for the sake of economy were executed really well. I enjoyed the style of the action, though was a little surprised by it (particularly during Nite Owl/Silk Spectre's attempted mugging). Again, I can see why a 'purist' might dislike it.

If the only information you're given is the concentration of an acid, you simply need to consider the equilibrium constant of dissociation (is it a strong acid - i.e. effectively full dissociation, or a weak acid?), and how many protons (H+ ions) are produced by each molecule of the acid. For example, a solution of 1 M HCl would give rise to a concentration of 1 M of protons. Weak acids involve a more complex calculation using the pKa.

"Does this rag smell like chloroform to you?" Worryingly, we've been chucking that one around as a lab in-joke for some time. That and something to the tune of, "would you like rohypnol in your tea? One lump or two?".

Not a problem. As I said, my work is in a related area, so most of the info was to hand anyway. It'd be nice to see a definitive answer come through, I might have another look in the literature if I find myself bored. Anyway- glad to be of help, good luck in your studies.

They seem to be an essential part of 'student wear' on my university's campus - those, and silly 'hippy' pseudo-headbands worn by the fairer sex ("I hate corporate fashion, but I love Topshop," seems to be the message).

International Hat Day? I don't think there are enough hats going about. Mostly stupid ones with ear flaps and bobbles. Whatever happened to the trilby? (Actually, scrap that - Pete Doherty appropriated it for the indie crowd...)

Right... CF3. Bit of simple maths to follow, don't worry too much about it. It's a matter of interpretation. What Hammett did was to take a standard reaction - the ionisation of benzoic acid derivatives at 25 C in water - and use it to compare electronic effects. pKa (-log of the equilibrium constant of the ionisation) is readily measured and can be used to determine the effect of substituents placed meta or para to the carboxylic acid group (those ortho to it would also have a steric impact upon the reaction - the benzene ring acts as a 'core', keeping steric factors constant). He came up with this equation: [math]\frac{log(K_{X})}{log(K_{H})}=\sigma\rho[/math] KX is the equilibrium constant of the benzoic acid with substituent X at m or p, and H is the standard - benzoic acid itself. Sigma is known as the substituent constant, and rho is the 'sensitivity' (which, for the reference reaction I'm discussing, is defined as 1). We're focusing on sigma. In this reaction, electron withdrawal increases the equilibrium constant by stabilising the acid anion. This manifests as a positive sigma value (negative sigma, conversely, indicates electron release). The sigma value is influenced additionally by the mechanism of withdrawal/release - particularly whether it is inductive (due to electronegativity) or resonant (due to conjugation). It is also influenced by whether the substituent is at the meta or para position on the ring relative to the functional group. Resonance effects are not detected from the meta position (try pushing 'curly arrows' round the benzene ring, and you'll see why), only para and ortho. Inductive effects, on the other hand, have an influence from both positions, and are stronger at meta as it's closer to the functional group. We would therefore expect that a purely inductive group, such as [math]NMe^{+}_{3}[/math], to have a larger magnitude of sigma at the meta than para position (whether positive or negative). Indeed, the data in Isaacs bears this out: sigma at the meta position is 1.04, and at the para position is 0.88. All good so far. CF3 is listed in Isaacs as another example of a purely inductive group. Dr Isaacs seems not to have checked his own data (but given the quality of the rest of the text I'll forgive him). He gives sigma meta and para values of 0.46 and 0.53 respectively for CF3. This contradicts the above discussion - which assumes CF3 is purely inductive. The data suggests that somehow, CF3 can also withdraw electrons through resonance. When I found this during a literature search last year I had a (very superficial) look through the literature for an answer, and discussed it with my supervisor. We first confirmed that this was not simply an error on Isaacs' part - a data book (not sure which) my supervisor has contained values of sigma from several sources, confirming the reversal of the expected trend. I then searched through some journals. It seems several competing ideas to explain this have been tossed about, including fluoride hyperconjugation, and overlap of F lone pairs with the benzene pi system. It doesn't seem that a consensus has been reached, despite this being recognised several decades ago, but I could be wrong - and as I said, it was a fairly quick search. But, to relate all this back to your original question. Given the sigma values for CF3, it would be reasonable to expect it to deactivate the ring to E.A.S., and direct meta. The link provided by UC should be able to explain why this is, etc. If you've got any questions on the above (or anyone else has corrections - I'm bashing this out quickly over lunch) I'd be happy to answer them. Kaeroll

Heh, I used to take a class with a Scouse lass. Someone made the mistake of saying "scoooone" and was immediately dubbed a "scon 'ead". It stuck.

The latter link gives me a session error - can you give me author/journal/etc?

I'm not aware of an online physical text book I'm afraid, but I'll find the relevant information and get back to you at the weekend if you're interested. This area is usually termed 'physical organic', as it's applying physical ideas and methods to organic chemistry - rather than simply saying "it's activating/deactivating", we can say how activating/deactivating it is, and so on. Louis Hammett was one of the first to quantify substituent effects, and as I mentioned above, CF3 is something of an anomaly in the data.

Got references? I ask not to challenge you but out of interest.

Sounds like a decent tutor to me. Do you have access to a decent library? If so Isaacs (or any other physical organic text) will be helpful with this kind of work. Key word: Hammett equation.

Frequency is proportional to energy - photons of high frequency have high energy and vice-versa. Radio waves are very low frequency, whereas UV is quite high. UV and higher frequency light have sufficient energy to break chemical bonds in your body and cause damage to your DNA, which is what can cause cancer. Radio frequencies (which are lower energy than visible light - you don't get cancer on your retina every time you open your eyes, do you?) are too low energy for this to happen. What insane_alien is saying is that RF waves don't interact with your body significantly, and even frequencies that can (such as microwaves) are generally not intense enough to cause any real damage.

Halogens are a special case in substituent effects. My current work deals with this area, though not halogen compounds specifically. CF3 would be expected to interact purely through inductive effects, as it cannot conjugate with the system. However, it actually exhibits a stronger substituent effect at the p- position than m- position, typical of substituents acting through the pi system. A few ideas about this have been investigated (inconclusively, as far as I'm aware) but it does seem that CF3 can release electrons into the pi system. I'd be cautious of interpreting the behaviour of CF3 purely in terms of inductive effects. A nice treatment of this is given in Physical Chemistry by Isaacs. If you don't have access to this, let me know and I'll pop to the library on Thursday and get the numbers for you. Out of curiosity, what level are you studying at? If you're at A level don't worry too much about it, but if you're at university it's quite and interesting problem.