Chemistry HL, P1, P2, TZ2 2012

I found the carbon dating ridiculous.... Apparently not many people got it other than the people who took physics. That's not chemistry! Also did anyone did the acid and base option in section B? I got ph of 11. Something and buffer ph of 9.25 I think 14-4.75

and yep buffer is 9.25! NH4OH was exactly equal to NH4+ ion conc coz half of the NH4OH reacted with HNO3!

if there are two bonding pair and 2 pair of lone like water it is sp3 hence a tetrahedral shape - 109degree the two lone pair will pull down a little hence angle is 105 degree but remember because of lone pair it should be sp3 due to four regions

If it was H2O like 2 bonding pairs and 2 lone pairs then its definitely sp3! Remember the orbitals in which the lone pairs are also combine to form new orbitals!

hey mamds, what did you get for a question asking for the reflux reaction with naoh as well i think, i got carboxylic acid formed. The question is in paper 1

I thought the pKa of the molecule was like 2.17 so the pkb was 11.83.

But it asked for the pkb of the conjugate base so I answered with the table with the 2.17 pkb.

I'm probably wrong though cause there were 3 11.83 options and only 1 2.17 and it's never the single one

There wasn't an amine group, but there were 2 amide groups which also validated my choice of carboxylic acid and amide.

Who knows though... who knows...

Hiii!

Does anyone remember the answer to the question on P1 about the electroplating?

I think it was 1 gram of Silver plated in one cell and then one was supposed to choose the alternative that represented how much was deposited on the other cell with Copper sulfate?

I chose (1/107) * (63/2) or something like that? I think its wrong though...

Yes, you were right the answer was C, the reason was that the oxidation number of silver was +1 where as in copper it was +2, there fore you get half the amount of coper because you need twice as much of electrons to produce the same mass of copper - if that makes sense.

The chem boundary won't be much below 80 if anything I think it will be over because the paper 2 was slightly easier then last yr's paper 2 and last yr's boundary for TZ2 was 81 and 70-90 for paper 2! Since paper 2 is more weighty it should be about 82-83!

did anyone do the section b question about conducting/not conducting? did you also write that one of them didn't conduct because it was molecular covalent and thus had no ions to transport charge and the opposite argument for the other?