Chem5 June 2014 Unofficial Mark Scheme

And I think the exothermic question in 1 is wrong. If energy was required, it would be endothermic

Is it not the case on the chromium question that one of the electron conifgurations has a 4s2 and the other one doesn't?

The question about chromium:

Both had the configuration [Ar] 3d3 because both had the oxidation state +3. The complex ions, however, had different charges due to the Cl- ligand on the second complex ion. The different ligands alters the ΔEso different frequencies of light are absorbed. This means that different frequencies of light are reflected, and so, two different colours are observed.

Isn't the correct configuration [Ar] 4s2 3d1
because if 3d3 then the 4s orbital is empty and the only case I know where you fill the 3d orbital before the 4s is with Scandium and zinc

Yep, dilute NaOH (or not in excess) will do the same thing. 2OH- goes to 2H20

how about KOH?

It's not a case of which is filled first, when the chromium is ionised the 4s electrons are always lost first so both of those are gone and then one from the 3d sub shell leaving [Ar]3d3

For reagents can you just say Cl- instead of HCl and CO32- rather than Na2CO3??

It's not a case of which is filled first, when the chromium is ionised the 4s electrons are always lost first so both of those are gone and then one from the 3d sub shell leaving [Ar]3d3

idk if someone has already said this but for the SiO2 4 marker,
they asked for the structure (1)
bonding (1)
and two properties of sio2 (2)