Edexcel replied quickly to my questions. My thanks to them. I’ll paste their answers exactly as they wrote them

1) The amine complex of Copper… will [Cu(NH3)4]2+ be accepted along with the shape name: tetrahedral, or must it be [Cu(NH3)4(H2O)2]2+ shape distorted octahedral {or something else?)

The copper complex will be acceptable but the shape is not tetrahedral but square planar or the octahedral shape with 4 ammonias and 2 waters which is the preferred answer. Response (John Apsey)

There is some confusion as to whether ‘green’ or ‘violet’ should be used for the colour of Cr(III) complexes. Sources seems to differ between the two. What should they write, particularly aqua complexes of that oxidation state.? Is either acceptable?

Hexaquachromium(III) is violet – no confusion (Ref 1). The green colour produced when Cr(VI) is reduced by, say, hydrogen peroxide, is due to one or more of the water ligands being replaced by an anion such as chloride or sulphate. If A level students say the hexaqua complex is green I doubt we would object, however. Response (Rod Beavon)

2) References to deltaS(tot)=RLnK avoid stating Kc or Kp. Whis is this? And what if a Kp was calculated using this formula?

The equation as given is derived from gas phase reactions using Kp, and applies only to those reactions. Using it for other systems is more complicated and involves the use of the activity of a substance when calculating the equilibrium constant rather than its concentration. Such considerations are beyond A level. (2) and (3). Response (Rod Beavon)

3) How to explain that the equilibrium constant is unchanged for a reaction such as CaCO3(s) <—-> CaO(s) + CO2(g) when the pressure increases? The thinking being: as P increases, to keep Kp the same (which is only supposed to change with changes in temperatre) the mole fraction must decrease in exact proportion to the pressure increase, but the amount of gaseous moles of CO2 divided by the total number of gaseous moles (as stated in George Facer’s A2 textbook) would be constant, hence make the mole fraction impossible to decrease in line with the pressure increase. Even if one considers the solid in the total number of moles, in this case the mole fraction value would be constant too, as an increase in CaCO3 from CO2 ‘recombining’ with CaO would be met with a corresponding decrease in the amount of CaO, the absolute total number of moles is also constant. It therefore seems impossible to me that this can be explained using A-level knowledge and I am at a loss to explain it outside the scope of A-level too. Little or no info is given in these questions about whether the reaction is done at constantant temp or constant volume.

The equilibrium constant for the reaction you state is equal to the total pressure: Kp = p(CO2). Therefore Kp is not independent of the total pressure for a heterogeneous equilibrium such as this. Response (Rod Beavon)

5) W.r.t. equilibrium, to what extent can students use the terms/expressions “Q” (e.g. Q < Kc), “numerator” and “denominator” in explanations of their answers for such questions? Do they have to define Q first before embarking upon using it in explanations?

I would be very happy with the use of Q provided it was defined. It shows a good awareness that to calculate K you need equilibrium values of concentrations or whatever. Response (Rod Beavon)

6) Is the term ‘charge density’ still rejected in explanations e.g. polarisation of s-block cations on anions?

We don’t reject it provided that candidates explain what they mean by it. Response (Rod Beavon)

7) When students calculate a heat change using Q=mc(deltaT) is it incorrect (i.e. would students be penalised) to include the – (or +) at this stage depending on whether the reaction was exo or endothermic respectively? Edexcel had not included the minus in these Q calculations in past years papers, only including the sign when deltaH has been calculated. I have advised students to include it on calculation of mc(deltaT) as a means to lessen the chances of leaving it off on calculation of deltaH

I don’t think they would be penalised, no. If the answer is correct and the working makes sense they get full credit. Response (Rod Beavon)

8) the variations of conditions and reagents used for the addition of HCN to carbonyls is very diverse in the literature. One of my highly trusted sources G.I.Brown’s Organic Chemistry (e.g. http://tinyurl.com/339em8a) says optimum conditions involve use of pH5 but edexcel are promiting alkaline conditions. What if a student gives non-alkaline conditions in their answer?

Any of the conditions which work are acceptable – and both of those that you mention have been properly credited in the past. However the pH8 conditions are mentioned specifically in March and references therein (4). The pH 5 reaction pathway is often performed using the bisulphite addition compound of the carbonyl compound and is used for aromatic aldehydes especially. Response (Rod Beavon)

9) Will KMnO4 and dil H2SO4 be accepted as a test reacgent to differentiate aldehydes from ketones (or indeed are they suitable reagents for the oxidation of primary adn secondary alcohols) or does it’s use cause the oxidative cleavage in ketones?

This would depend on what had gone before in the question. If you get to the stage of knowing that something is either an aldehyde or a ketone then it would be OK. I don’t think acid manganate(VII) would attack a ketone in the cold. Response (Rod Beavon)

10) Will the students be given theoretical 1H NMR spectra (as as that obstined by programs like ChemBioDraw) or actual NMR spectra such as those at SDBS (http://tinyurl.com/3cx9mo)?

We have tended to use real spectra cleaned up somewhat. Response (Rod Beavon)

11) There are numberous mistakes in the Edexcel endosed testbooks. If a student was to replicate a mistake would they get penalised?

I can’t answer this in general since such circumstances are dealt with on a case-by-case basis with discussion at the examiners’ meeting. My own view is that textbook mistakes do not over-ride the way that the Universe works. If a student makes a nonsensical claim based on a textbook error I would have expected the teacher to have dealt with this and therefore I would probably not credit the answer. Response (Rod Beavon)

References.
(1) Greenwood NN and Earnshaw A, ‘Chemistry of the Elements’. Pergamon Press 1984, p1197.
(2) Kneen WR, Rogers MJW and Simpson P, ‘Chemistry – Facts, Patterns and Principles’. Longman 1985, p782.
(3) Atkins PW, ‘Physical Chemistry’. OUP, 1978, pp 256 – 259.
(4) March J, ‘Advanced Organic Chemistry’. Wiley, 4th ed 1992, pp 964-5.

Again, thanks to the edexcel advisors for their speedy answers. It is stark contrast to what happened to ALM 8M1 and 8M2 Jan exams when they didn’t reply despite sending me a response number. On a personal level, I would have liked a bit more of a firm answer to some of the Q’s but for now that’s how things stand.