AQA CHEM 1 (unofficial) Mark Scheme

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]

(edited 11 years ago)

Scroll to see replies

Reply 1

KSS

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

Reply 2

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 >_<

(edited 11 years ago)

Reply 3

NickEHarry

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

Reply 4

Mystic Creature

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

Thanks for this btw

Reply 5

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

Reply 6

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 :wink:

Heck, they gave two lines to write it :biggrin:

(edited 11 years ago)

Reply 7

navy

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

Reply 8

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?
:smile:

Reply 9

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 :frown:

Reply 10

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?
:smile:

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

Reply 11

MediterraneanX

Original post by Mystic Creature

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

Thanks for this btw

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

Reply 12

Meggles

Surely for 2ci you could have C8H18 and C7H14?

Reply 13

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 :wink:

2 marks seem to have dissapeared :0

Reply 14

kpmarshall

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

Reply 15

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?