EwenM

"No-one is born depressed and suicidal for no reason until external factors are introduced" But there does seem to be some genetic pre-disposition to depression. Not everyone responds to depressing external factors by becoming clinically depressed. There are many factors, and the role of these factors appears to vary from case to case.

Why the concern over whether mental illness is associated with changes to the brain? Either (a) the mind is the brain and therefore any mental process will be associated with a physical change or (b) the mind has some separate existence independent of the brain. Only in the case of option (b) could we totally dismiss the notion that physical intervention (drugs, ECT, even surgery) would hold out hope for alleviating the symptoms of mental illness. Has anyone 'cured' depression? Do talking therapies simply help people cope with the symptoms? Are drugs any better? Why avoid one sort of help?

'Depression and how to survive it' by Spike Milligan and Anthony Clare is a good read. A couple of points from the book: Depression is a deadly disease, causing death by suicide and disabling people for large chunks of their lives. Long-term use of antidepressants is non-addictive and has been shown to help reduce relapses. Don't confuse antidepressants with tranquilisers. The causes of depression are complex and involve physiological, psychological and social factors. The cognitive theory is one of many, but are distortions of perception the cause or just an effect of depression? If you encounter someone with depression (or are depressed yourself) remember that (i) they/you cannot possibly 'snap out of it' and (ii) things will get better, and the more quickly they/you seek help the better. I'll listen to Tom Cruise's views on psychology when he listens to my views on his film career!

"The Chemist's rule: Never take more than three data points. There will always be some kind of graph paper on which they fall in a straight line. "The Chemist's rule, first corollary: if you have only one kind of graph paper, never take more than two data points." 8-)

Good: Ethyne (acetylene) smells of lychees Bad: Butanoic acid smells of vomit. Interestingly, you can get rid of the smell of vomit by scrubbing with sodium hydrogencarbonate (a weak alkali) which seems to neutralise things like butanoic acid.

No, you have the wrong expression for Kc: Kc = [i2] [Cl2] / [iCl]^2 (That's divided by the concentration of ICl squared - sorry about the formatting). Because [i2] will be equal to [Cl2] you can simplify this by taking the square root: [Cl2]/[iCl] = sqrt(Kc) [Cl2] turns out to be 2.91 x 10^-3

I'd like some information about the strange ionic compound caesium auride to complete a Born-Haber cycle about its formation. I thought it would make a change from NaCl! Does anyone know its enthalpy of formation or its lattice enthalpy? I've looked in every text we have and scoured the web, but without luck. For the curious, Here's what I do know: CsAu is ionic, with the Au- anion in a lattice that closely resemble CsCl. The Cs-Au distance is 369 pm. Atomisation enthalpies are 78.7 kJ/mol for Cs and 369 kJ/mol for Au. The ionisiation energy of Cs is 375.7 kJ/mol and the electron affinitiy of Au is -222.8 kJ/mol.

It doesn't matter how dissociated the H2SO4 is, the maximum [H+] it can give is 0.02 M, which corresponds to a pH of 1.7. To reach pH 1.4, [H+] must be 0.04 M - impossible with 0.01 M H2SO4

" as ionic bonds only occur between a metal and a non-metal, a covalent is between gas and gas, metalic bond between metal and metal.... unless there are exceptions that I don't know about!" What about the ionic bonding in ammonium sulphate, where the cation has no metal. Or ammonium dichromate, where the anion has a metal but the cation does not? Covalent bonding does not occur exlusively between gases: carbon disulphide is covalent, for example. Nor is it limited to non-metals, although with metals the bonding is usually termed 'dative covalent' or somesuch e.g. MnO4- Ionic and covalent bonding are extreme types of bonding, and most bonding is a blend of the two types.

This 'isopropyl alcohol' stuff was a 1960s attempt to make systematic names and it's still widely used although the systematic names have moved on. 'iso' refers to 'isomer' not 'equal'. For example 'isobutyl alcohol' is what we now should be calling butan-2-ol. 'Methyl', 'ethyl', 'propyl' etc are the names for an alkane chain attached to the main structure by its first carbon. The old system used to add an 'n-' for these simple chain e.g. 'n-butyl alcohol' (butan-1-ol). The '-yl' ending has nothing to do with the '-yne' ending that denotes a triple bond. The old system for a branch with, say, four carbon atoms was to call the branch 'butyl' and then add 'n-' if the branch was attached by its first carbon and 'iso' (or 'i-') if it was attached by its second carbon. If the branch was itself branched then it was called 'tertiary-', 'tert-' or just plain 't-'. To take nonane as an example (we need 9 carbons in the main chain so that the butyl sidechain is not considered as the mainchain): Modern name Older name butylnonane n-butyl nonane (1-methylpropyl)nonane isobutyl nonane (dimethylethyl)nonane t-butyl nonane Note that brackets are used to indicate that, for example the methyl in (1-methylpropyl)nonane is attached to carbon-1 of the propyl sidechain, not to carbon-1 of the nonane.

I teach IB Diploma Chemistry. Best course I've taught, I wish I'd had the chance to take it when I was that age.

Cis and Trans: shouldn't they be reserved for cases where there are two hydrogen atoms on the same/opposite sides of the double bond (e.g. 1,2-dichloroethene)? E and Z were taught to me as superior to cis and trans because the CIP system clarifies which groups have priority. Cis and trans is a bit vague but OK with hydrogens.