AQA AS Chemistry Paper 1 2018 Unofficial Mark Scheme

Can people write the questions as well as the answers pls? I can't remember the questions from the exam.

Na has more shielding as it is a new period, therefore F is smaller

Also did anyone else get -2 Kj mol^-1 for the Change in Enthalpy because that’s what I got and I feel like it’s wrong

wait, what was the question for the enthaly one

Also did anyone else get -2 Kj mol^-1 for the Change in Enthalpy because that’s what I got and I feel like it’s wrong

was the mr 72.4, first few answers 1210 ppm and 0.854kg and x = 5.68
and the mass of KI was 19.7g?

Isn’t x 6? Aren’t you meant to round it cus it’s empirical formula?

How were u sopose to find x on the water question ratio :/

Also did anyone else get -2 Kj mol^-1 for the Change in Enthalpy because that’s what I got and I feel like it’s wrong[/QUOTE

Find the mass of water made then use n=m/mr. Also find mass of na2co3 and use n=m/mr to find n. Then find the ratio of the number of moles of na2co3 to h2o

Does anyone know what the 60cm and 30 cm gas mulitpile choice question was and the answer. Think I put 40 or 50

I put 50 but ngl I semi guessed.

Disclaimer: These are my own answers and I have no idea whether they are right or not. I also can’t remember the order of the questions very well. Please bear with me.

Thank you to: @Clarareeves2001, @Vanilla Twilight, @SaraFreire14, @mathsguy5503, @MissMilkshake

1))
I said that there is a positive nucleus in the atomic model but the plum pudding model suggests that the entire atom is positive. I also said that electrons surround the nucleus in orbitals/shells in the atomic model whereas the plum pudding model states that the electrons are dotted within the atom.
Can’t remember the next part.
R was nitrogen. I think it was Be3N2 or something like that...?

2))
1210ppm
Something along the lines of 2300ppm
I think 0.831-ish kg?
Were there any more parts?

3))
Can’t remember

4))
6-mark q
I think most people will have missed the fact that they were solid samples. You had to add water to make them aqueous.
Carbonate: Add HCl and observe fizzing
Na2CO3 (aq) + 2HCl (aq) —> CO2 (g) + 2NaCl (aq) + H2O (aq)
Fluoride and Chloride: Add acidified AgNO3. DO NOT ACIDIFY WITH HCl, white ppt formed with chloride, no ppt formed with fluoride
AgNO3 (aq) + NaF (aq) —> AgF (aq) + NaNO3 (aq)
AgNO3 (aq) + NaCl (aq) —> AgCl (s) + NaNO3 (aq)

5)) 6)) 7)) 8)) 9))
Can’t remember the specific order

Equilibria q:
3 minutes. b/c equilibrium is when rate of forward and backward reactions are the same so the concentrations of the reactants and products is CONSTANT.
T2 was higher because eqm shifted right, and because it was an endothermic reaction, it shifted right to lower the temperature, meaning the temperature must have increased from T1

Mass spec q:
time: 6 point something times 10^-4. It was of the same order as the time for the 79Br+ ion.
It’s detected because the ions hit a negative plate that gives the ions electrons. The number of electrons given corresponds to relative abundance of that ion.

The Syringe q:
Mr was like 74/5-ish?
The Mr would be bigger because the volume of gas would have decreased so no. of moles would decrease but the mass would be greater so overall, the Mr would be bigger than actual.

Bonds q:
KrF2 was supposedly linear. Bond angle: 180 Drawn with 2 bond pairs and 3 lone pairs. (I put down trigonal bipyramidal and bond angle: 86, which is wrong but I can hope they'll 'accept' or 'condone' it )
Can’t remember exact q but it was something about a V-shaped molecule and you had to say something about the lone pairs and that the angle would be reduced to 104.5

The Hydrated Salt q:
x was 5.68
The next bit asked why the calculated value was less than 10. It was b/c not all of the water would have evaporated from the salt so you had to heat for longer.

A q about Intermolecular forces in SiF4..
Should have been van der Waals b/c although Si-F bond is polar, SiF4 is a symmetrical molecule so polar charges cancel.

A q about Atom Sizes:
Na is smaller than F because it has a larger nuclear charge. They have the same number of electrons so they have the same orbitals but b/c Na has a larger nuclear charge, it pulls the electrons closer to the nucleus so that the atomic radius of Na is smaller.

chlorine q:
Cl2 + H2O —> HCl + HClO
Oxidation half-eq: Cl2 + 2H2O —> 2HClO + 2H⁺ + 2e^-
Reduction half-eq: Cl2 + 2H⁺ + 2e^- —> 2HCl
There was a next part but I can't remember it

MCQs:
Not in any particular order...

1. TiO2/TiCl4 question: Magnesium
2. Group 2 graph question: Melting point
3. Volume question (¹/₂ Xe + ³/₂ F₂ ...): 50 cm^3
4. HI + H₂SO₄ or something?
5. Titration experiment questions (5x)
6. Mg(OH)2 is used to treat indigestion
7. NH4Cl shows ionic, covalent and dative covalent bonds.
8. BaSO4 can be used in medicine or something like that because it doesn't dissolve in bodily fluids.


Yeah, I can’t remember them very well but if anyone does remember anything, please comment below.

I don't even know how u calculate it but I think there was one like it on the 2016 paper

i said F was smaller as its in period 2 whereas Na is in period 3, so F has less shells hence smaller