AQA AS 2016 - CHEM1 (Resit) Unoffical Mark Scheme

but when i did the calculation it came out as 32. something how did you get 28??

The m/z x abundance + mz x abundance... / 100 = 28.065

You might have misput it into your caclulator.

how many marks do i lose? i did the correct calculations

For the last question, surely it was method 2 because the first method was not 100% atom economy as it had 2 steps?

EDIT: Thanks to everyone who has helped in this thread. If anyone can remember the marks for each question I will add them in for you guys! Also the Bold stuff after some thought are probably the correct answers or something along the lines of it. Good luck to everyone in the rest of their exams

Here is my unofficial mark scheme. Anything in bold I am not sure if it's right. So if you have any idea then please tell me so i can add it! If i have missed anything out then aslo let me know!

Section A

1.
a) Relative Atomic mass Definition
b) Magnetic Field
c) - Ions accept electrons -Current is formed which is proportional to abundance
d) Something like 28.065 for the RAM
e) Similarity= Peaks still at original m/z values becuase +1 ions are still formed/
same relative abundance (or same height of peaks) because same sample is used so similar amount of the isotopes are present
-Difference - Peaks at half the m/z values becasue high energy electrons will produce +2 ions

2. (Can't rmember what topic this was. I think it was about Van Der Waals)
a) -Electron Density randomly shifts -Creating areas of +ve and -ve charge on molecule - Attraction between molecules which is intermolecular force/VDW
b) O-H bond big electronegative difference allows for hydrogen bonds. Hydrogen bonds are stronger than VDW.
c) Fractional Distiallation will sperate these
d) The Se molecule is larger. This means the VDW forces are stronger between molecules

3. (Questions about Alkanes?)
a) Group is alkane
b) 2,2,4 - trimethylpentane (might accept 2,4,4 - trimethylpentane)
c) C₈H₁₈ + 12.5O₂ ------> 9H₂O + 8CO₂
d) but-1-ene
e) C₁₄H₃₀
f) Thermal Cracking. High temp and high pressure
g) Isomers question. Chain isomer = H₂C=C(CH₃)₂ Postion isomer = But-2-ene Functional Isomer = Cyclic Alkane so cyclicbutane

4. (The weird reactions and the shapes question?)
a) Balancing equation I couldn't remember
b) Cu₂(OH)₂CO₃ + 4HCl -----> 2CuCl₂ + 3H₂O + CO₂
c) Effervescense
d) Cu₃O₈H₂C₂ or in the structural form
e) Shapes question - SF₆ = Octohedral , 90 degrees -SF₄ = See-Saw shape. Lone pair on the horizontal plane. Angles 90, 120 or 180 degrees. Probably will accept -2.5 degrees off each angle.

Section B

5. (Period 3 stuff)
a) - Ionisation energies increase -Increasing proton number - Similar Shielding -Attraction between outer electron and nuclues gets stronger -The bigger nuclear charge reduces atomic radius (I don't think this point is needed)
b) -Silicon has highest melting point. -Because of macromolecular/Giant covelant structure. -Strong covelant bonds throughout structure. -Requires high amounts of energy to break.
c) The elements that you could say were Aluminuim because removing electron from 3p shell and Sulphur because of pair repulsion.
d) -Element Y is Sulphur. -Large jump in eneries from 6^th to 7^th ionisation enegies -So 7^th electron in inner shell so sulphur must be the element Y.

6. (Calculations)
a) 0.113m³ (3 sig figs needed)
b) 1065 Kg or 1.065x10⁶ g
c) Percentage yield = 49.3%
d) Method 1 because its 100% atom economy. Only producing one product.

For that VDW forces question, I put that, because electrons are not fixated but are rapidly moving, temporary dipoles are formed, there is attraction between delta + and delta -,... then i drew a sketch similar to that found in the aqa as nelson thornes book (under the intermolecular forces chapter).
(I did not mention 'atoms' 'molecules' im pretty sure i didnt)
I highly doubt I got any marks. But what do you think?

Cool,I got the same answers :]

For the last question, surely it was method 2 because the first method was not 100% atom economy as it had 2 steps?

You work out the theretical yield of mass you get which was about 2210.88g and use that against the afctual yeild to get the percentage yield.

1.09x10³ / 2210.88 = 0.493

X 100 = 49.3%

Cracking question,i just put high temperature is that enough?

Hello there,
I think the questions asked for 2 conditions :/, but did you put thermal cracking though?
I've put high temp (700 degrees)
High pressure ( >1000kPa)