[knocker]

FULL (unofficial) MARK SCHEME

1(a) p=37
n=48

[2]

(b)(i) e- gun fires high energy e- which knock off an e- from an atom of the sample.

[2]

(ii) Rb(g) --> Rb+(g) + e-

[1]

(c) Rb has a larger atomic radius / more shielding therfore less energy needed to remove e-

[1]

(d)(i) s-block

[1]

(ii) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1


[1]

(e) 85.6

[3]

(f) detector
Ions hit the negatively charged plate which produces a current. The size of the current is proportional to the number of ions hitting the plate.

[2]

(g) Sr smaller than Rb
Increased nuclear charge/number of protons. Electrons added to the same energy level.

[3]

2(a)(i) CnH2n

[1]

(ii) Fractional distillation

[1]

(b)(i) but-1-ene

[1]

(ii) structure of cyclobutane or methylcyclopropane

[1]

(c)(i) C15H32 --> 2 C4H8 + C7H16

[1]

(ii) (Thermal) Cracking
High demand for X / more valuable

[2]

(iii) To break to the covalent carbon-carbon bonds

[1]

(d)(i) H2

[1]

(ii) Fuel

[1]

(iii) C4H10 + 2.5 O2 --> 4 C + 5 H2O

[1]

(iv) SO2
CaO or CaCo3

[2]

(v) Fluegasdesulphurisation (or neutralisation/scrubbing?)

[1]

(e) Both only have vdw IMF's the strength of which is dependent on size. X and Y are similar size so will have similar vdw forces.

[2]

3(a) trigonal pryamid with one lone pair (same as NH3)

[1]

(b) dative / co-ordinate
both electrons for the bond come from the P atom.

[2]

(c) 109.5 (tetrahedral angle)

[1]

(d) The difference in electronegativity between P and H is not great enough to deshield the H atom.

[1]

4(a)(i) macromolecular

[1]

(ii) delocalised electrons which are free move and carry charge

[2]

(iii) many strong covalent bonds must be broken

[2]

(b)(i) metallic

[1]

(ii) strong electrostatic attraction between titanium cation and delocalised electrons.

[2]

(c)(i) the layers of Ti atoms can slide over each other

[1]

(ii) same crystal structure and bonding (?)

[1]

(d) Ionic
strong electrostatic attractions between oppositely charged ions.

[3]

5(a) PV=nRT
P=100,000 V=0.005 R=8.31 T=298
n= PV/RT = (100,000*0.005)/(8.31*298) = 0.201908

moles B2O3 = 0.201908 / 5 = 0.0403816

mass= moles*Mr = 0.403816 * 69.6 = 2.79 grams (3s.f.)

[5]

(b) B + 1.5 Cl2 --> BCl3
3 bonding pairs of electrons repel equally

[3]

(c)(i) moles BCl3 = mass / Mr = 43.2 / 117.3 = 0.368

moles HCl = moles BCl3 * 3 = 1.10

conc = moles / volume = 1.10 / 0.5 = 2.20 mol/dm3

[4]

(ii) H3BO3 + 3 NaOH --> Na3BO3 + 3 H2O

[1]

(d) Atom economy = (B)/(3HCl+B) * 100 = (10.8)/(120.3) *100 = 8.98%
Sell the HCl produced as well

[3]

(e) EF = BCl2
MF = B2Cl4

[4]

[KSS]

For 5b can you have 2B + 3CL2 ---> 2BCL3

[The Assassin]

(iv) SO2
CaO or CaCo3

Ah damn! If I put the names there would I get it wrong? Did it specify to write the formula? Should've read it properly >_<

[NickEHarry]

you think you could put scrubbing instead of Fluegasdesulphurisation? because I think they are the same aren't they?

[Mystic Creature]

I wrote neutralisation instead of flue gas desulfurisation..hopefully they give the mark!

Thanks for this btw

[Mystic Creature]

(Original post by KSS)
For 5b can you have 2B + 3CL2 ---> 2BCL3

I think so, normally multiples are allowed. Unless the questions said specifically to form one mole bcl3, then you're fine

[Mystic Creature]

(Original post by The Assassin)
(iv) SO2
CaO or CaCo3

Ah damn! If I put the names there would I get it wrong? Did it specify to write the formula? Should've read it properly >_<

Don't worry, I wrote out the names too. There is nothing wrong with that, and no they didn't specify

Heck, they gave two lines to write it

[navy]

wasn't it but-2-ene? not but-1-ene?

[alt31]

heyy i don't know if my heads frazzled but i can counts 71 marks up there...
was the scrubbing/flue gas desulfurisation only one?

[Mystic Creature]

(Original post by navy)
wasn't it but-2-ene? not but-1-ene?

Compound X was but-2-ene yes, but the question was asking for a position isomer of compound X, so it's but-1-ene..i got that one wrong too

[Mystic Creature]

(Original post by alt31)
heyy i don't know if my heads frazzled but i can counts 71 marks up there...
was the scrubbing/flue gas desulfurisation only one?

I believe you are correct, and you have spotted the mistake I think..I'm sure knocker will change that asap

[MediterraneanX]

(Original post by Mystic Creature)
I wrote neutralisation instead of flue gas desulfurisation..hopefully they give the mark!

Thanks for this btw

I wrote desulfur-fluisation...might put a smile on the examiner's face!

[Meggles]

Surely for 2ci you could have C8H18 and C7H14?

[alt31]

for 2e) do you think saying the carbon chains are the same length would get you a mark (for bp of X and Y?) I forgot to mention VdW

also for 4cii) I thought metallic bonding wasnt in layers :s thought it was just graphite that was layered :s

really freaking out, can only count 55 marks, and i really really need an A! :'(
i know 7 are definitely wrong but theres 6 that im unsure of.
and just notice how crappy my counting is today 2 marks seem to have dissapeared :0

[kpmarshall]

So how many marks do we think we got? Someone set up a poll? (Because I don't know how....)

[Shafski]

Hmmm.. probably lost 15 marks at most, if I have a harsh examiner. Hopefully grade boundaries drop.

So mad I messed up on 2 of the calcs, they're usually my strongest point! I did the method right so will I get error carried forward for dividing by the wrong amount for moles ratio?

And empirical formula, wilL I get marks if I did the method right but put the wrong MR values?

[Meggles]

For 3d)iii could not have carbon monoxide produced?

[knocker]

(Original post by Meggles)
For 3d)iii could not have carbon monoxide produced?

No it asked for a solid product (C).

[knocker]

(Original post by Meggles)
Surely for 2ci you could have C8H18 and C7H14?

No it said it produces 2 molecules of X (2 C4H8) and one other product.

[knocker]

(Original post by The Assassin)
(iv) SO2
CaO or CaCo3

Ah damn! If I put the names there would I get it wrong? Did it specify to write the formula? Should've read it properly >_<

Names will be fine - it didn't specify