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# AQA Chemistry New AS Unofficial Mark Scheme

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1. (Original post by A.aaa)
How did you do it?
1.052g total in the solid, from memory. BaSO4 is the ppt as it is insoluble in water. Mass of ppt was something around 0.78, I think. (137.3/233.4) is proportion of Ba in BaSO4. So, (137.3/233.4)*0.78 (or whatever it was) is mass of barium in ppt. This is therefore the mass of the barium in the BaCl2.

I used that to find the mass of the Cl in the BaCl2 using the fact that Cl ion is 1- and Ba ion is 2+. Therefore, you can find that the mass of the BaCl2 is 0.681 (from memory) and from that you can find the proportion of the MgCl2 in the solid at the start.

Could be wrong though!
2. For the one that gave 2 circles with ammonia and you had to calc the mass of ammonia using the ideal gas equation, did anyone else get a number like 770kg? I know a few people who got something like 2x10^-7 kg
3. (Original post by rosemondtan)
so if I make two of these, the other one would be completely wrong? Oh man....
Nah. CE = 0 is only used when you say something chemically incorrect. For maths questions I cannot even think of an example where this is used. The main example of it is in "Why is this compound melting at a higher temp than this other compound?" where you use bonding to explain it.

If you make two mistakes, such as subbing in an incorrect Mr, you'll lose one mark for accuracy/method for each one, so two marks lost in this example, most likely.
4. (Original post by rlr123456789)
For the one that gave 2 circles with ammonia and you had to calc the mass of ammonia using the ideal gas equation, did anyone else get a number like 770kg? I know a few people who got something like 2x10^-7 kg
I got 0.69g of ammonia
5. (Original post by rlr123456789)
For the one that gave 2 circles with ammonia and you had to calc the mass of ammonia using the ideal gas equation, did anyone else get a number like 770kg? I know a few people who got something like 2x10^-7 kg
0.695???grams ??? but i rounded it to 0.7 because i assumed it was to 1.s.f
6. (Original post by rosemondtan)
lol omg it's so scary because if I add all the marks I've lost (assuming I get the entire question wrong) it's 10 marks but if i count method marks it's only 5 so idk omg lmaO)
Did you say that chlorine was displacing the iodide to form brown solution?
And for the gas mc question, was the total amount of gas 30cm3?

You start with 30 of A (can't remember), 20 of B and 0 of product. The mole ratios were 11, so 20 of the product forms but as 10 of A is in excess it remains
so 20+10=30??
7. (Original post by DaVinciGirl)
What is the full electronic configuration of Al? 1s2,2s2,2p6,3s2,3p1

What is the full electronic configuration for Cr+3? 1s2,2s2,2p6,3s2,3p6,3d3

What is the formula of the ion with same electronic configuration of Krypton?
Sr2+ (strontium)

What compound has a +2 and -3 ions and has the same number electrons as Argon?
Ca3P2

Which ion has a smaller atomic radius Mg2+ or Na+?
Mg 2+
because has the same number of electrons, same shielding but more protons. So greater nuclear charge and attraction for outer electrons.

What is the first ionisation energy of Na?
Na (g) --> Na+ (g) + e-
Diagram-Mark where the Mg or was it Si?
Was and then mark the point where Sulphur was on the First ionisation graph.
Mg/Si should have been above so the line was increasing.
Sulphur should have been below Phosphorus but above Silicon.

Why does Sulphur have a different first ionisation energy compared to Phosphorus?
-Both have same shielding and in the same orbital the 3p orbital
-Sulphur is paired with an electron in the 3p orbital whilst Phosphorus isn’t
-There’s repulsion between the negatively charged electrons
-So electrons are easier to remove

What is the method of making a standardised solution of 250cm^3? (6 marks)
-Weigh out known mass on weighing boat using a mass scale
-Remember to deduct the mass of the weighing boat to find the exact mass of the solid. (or zero the scale mass)
EDIT: You may not need this part as you've been told the known mass
-Then transfer the contents into a beaker. Use distilled water to make sure all solids are in the beaker.
-Then add bit more distilled water
-Stir with a glass rod to make sure it's all mixed
-Then pour solution into a Volumetric flask using a funnel
-Clean the funnel with distilled water
-Then fill the volumetric flask to the 250cm^3 mark. At near the mark use a pipette to add water dropwise and until meniscus is on the mark line.
Then place stopper on it. Twist the volumetric flask a few times to ensure it's all mixed.

Find mean titre value.
Ignore the first number as it was the rough one when calculating mean.
EDIT: You were only supposed to use 2 values that are 0.1 part when calculating mean.

What was the concentration of the solution.

Student titrated, what should she to improve her methods so there's a smaller percentage uncertainty?
-Titrate a greater volume of solution
-Why? So there's a greater value as percentage uncertainty= uncertainty/value *100. Bigger volume means there's a greater titre value.

Why does Bromine have lower boiling point than Magnesium?
-Bromine has a simple molecular structure.
-There’s weak Van der Waals forces between molecules.
-So smaller amount of energy needed to break these forces.
-Magnesium has a metallic lattice.
-It has many strong metallic bonds.
-Bonds formed from the strong attraction between positiveions and delocalised electrons.
-The metallic bonds are stronger than the Van der Waals forces

How do the ions get accelerated, detected by ToF and how abundanceis measured?
- Accelerated by negative electric field
-The ions reach the detector and generate a small current, which is fed to a computer for analysis. The current is produced by electrons transferring from the detector to the positive ions. The size of the current is proportional to the abundance of the species.

Calculation to find mass of one ion.
1/Avogadro constant * mass. Then divide by 1000 to put it in Kg.
Using kinetic energy, find velocity.
Starts with 1........ Quite a large number.

Draw the spectrum of Br2 with two isotopes of equal abundance.
Attachment 539511

Suggest why Magnesium has a longer melting point than Bromine. (Something like that?)
-It has much more bonds than Bromine. So more bonds are needed to be broken when melting.
a) Calculate the mass of Ammonia in Q?
Basically use the ideal gas equation and usethe temp given, multiply the pressure by 1000 to convert it to SI Units, divide the volume by a million to convert to m^3 . Then use everything given to find the number of moles in Ammonia. Then find the mass of Ammonia using the mr.
b) Calculate the volume in P given that the temperature decreased by 5 degrees and the total pressure is 75kPa?
-Find volume of the whole system with the new values and use moles from previous question
-Then subtract from the volume of Q given.

Draw NH3 and AlCl3 and write the bonding angle.
NH3- 1 Lone pair and 3 bonding pair. Should have drawn a trigonal pyrimidal.
Bond angle- 107

AlCl3- 3 bonding pair so Trigonal Planar
Bond angle- 120

What type of bond between NH3 and AlCl3 to make 3HNAlCl3?
Dative covalent
Electron pair donated from NH2 to AlCl3.

What is the half equation of Chlorate(I) into Chlorine?
2ClO- + 4H+ +2e- ---> Cl2 + 2H20

What is the redox equation of Sodium Chlorate(I) and HCl?
I have no idea.

What's the observation when colourless Potassium iodide and Sodium Chloride are mixed and what reaction occurred for this to be seen?
There was a brown solution seen, as Iodine ion was reduced to Iodine.

Question on Anhydrous Magnesium Chloride and Anhydrous Barium Chloride mixture. Water was added and Sulphuric acid too. White precipitate was formed. What was this an find percentage of Magnesium in mixture?
Barium Sulphate.
Calculation:

Multiple Choices:
-Brown Colour is from the Reactant and forward is exothermic.
-Empirical of hydrocarbon with 9/11th Carbon- C3H8
-Doubts about biggest dipole. I put down BF3 and checked in my CGP book and states that bonds with electronegativity differences would make a dipole. Others argue that its Carbon one because BF3 is not polar.
-Group 2's ionisation energy decreases downwards
-There's 50cm^3 of gas in the end.
-Gold is 19.3
-SiO2 was Macromolecular
-Balance was 4:7
-The reducing agent was C204
-How much sulphuric acid needed? D
-Heavier isotope took longer in ToF
-H2 Molecules was 1.81* 10^24
For the last question, can't quite remember what it was, but it was 3.2 moles of N2 formed right?
8. (Original post by rlr123456789)
For the one that gave 2 circles with ammonia and you had to calc the mass of ammonia using the ideal gas equation, did anyone else get a number like 770kg? I know a few people who got something like 2x10^-7 kg
I got something much smaller than that, less than a gram if I remember correctly (I cannot remember, though). I also doubt that is able to be the answer because NH3 is in gas phase and I doubt nearly a metric ton of NH3 would fit inside that container.
9. (Original post by haes)
0.695???grams ??? but i rounded it to 0.7 because i assumed it was to 1.s.f
i left 0.69g, i got the next part wrong tho
10. That was confusing, i just drew two lines. How do you work it out?
11. (Original post by haes)
0.695???grams ??? but i rounded it to 0.7 because i assumed it was to 1.s.f
Sounds about right. I can't speak for the rounding.
12. (Original post by britishtf2)
I got something much smaller than that, less than a gram if I remember correctly (I cannot remember, though). I also doubt that is able to be the answer because NH3 is in gas phase and I doubt nearly a metric ton of NH3 would fit inside that container.
i did think that at the time but didnt have enough time to correct myself but i also think that is very low
13. Guys for the gas mc question, was the total amount of gas 30cm3? You start with 30 of A (can't remember), 20 of B and 0 of product. The mole ratios were 11, so 20 of the product forms but as 10 of A is in excess it remains so 20+10=30??
14. (Original post by britishtf2)
Nah. CE = 0 is only used when you say something chemically incorrect. For maths questions I cannot even think of an example where this is used. The main example of it is in "Why is this compound melting at a higher temp than this other compound?" where you use bonding to explain it.

If you make two mistakes, such as subbing in an incorrect Mr, you'll lose one mark for accuracy/method for each one, so two marks lost in this example, most likely.
Oh for one question I used the wrong Mr and another question I used 3 titre values instead of 2 lol I hope I don't lose all the marks.
15. (Original post by RIDDHI7)
That was confusing, i just drew two lines. How do you work it out?
For the ammonia question? Use PV=nRT (oe) to find moles. Use Mr to find mass.
16. (Original post by haes)
0.695???grams ??? but i rounded it to 0.7 because i assumed it was to 1.s.f
I gave it to 3sf - because all the data was given to 3sf.
But there was one thing: the "300K" was what probably made you think it was 1sf? How do you know 300 was to 1sf? What if it had actually been 300.1 and hence it was rounded to 300 (3sf)? Or, as you say, it could have been 310 and it was rounded to 300 (1sf). The thing is, we can't tell.
AQA should have given 300 as 3.00 x 10^2-->because when using standard form, one can always tell what standard figures are being used. Would recommend that you give your answers in standard form, e.g.
Say you got an answer of 177200-->rather than writing 177000 to 3sf, it is better to write 1.77 x 10^5, because this makes it very clear without a doubt that you are indeed giving to 3sf.
17. (Original post by rosemondtan)
Oh for one question I used the wrong Mr and another question I used 3 titre values instead of 2 lol I hope I don't lose all the marks.
Oh you won't lose all the marks for that. First error lose 1 or 2 (if they are being mean) probs. Second error lose 1, I would think.
18. (Original post by britishtf2)
1.052g total in the solid, from memory. BaSO4 is the ppt as it is insoluble in water. Mass of ppt was something around 0.78, I think. (137.3/233.4) is proportion of Ba in BaSO4. So, (137.3/233.4)*0.78 (or whatever it was) is mass of barium in ppt. This is therefore the mass of the barium in the BaCl2.

I used that to find the mass of the Cl in the BaCl2 using the fact that Cl ion is 1- and Ba ion is 2+. Therefore, you can find that the mass of the BaCl2 is 0.681 (from memory) and from that you can find the proportion of the MgCl2 in the solid at the start.

Could be wrong though!
I can understand how you worked it out. I used another method by working out the number of moles using moles=mass/mr of baso4 then i wrote the equation bacl2+h2so4=baso4+2hcl and everything is a 1:1 ratio so the same moles of bacl2 were used. I worked out the mass of bacl2 from this using the mass=mr x moles. Then i took this away from the mass of both bacl2 and mgcl2 to work out how much mgcl2 there was. My answer was also 35.5% 👍🏿👍🏿
19. (Original post by mbb123mbb)
I gave it to 3sf - because all the data was given to 3sf.
But there was one thing: the "300K" was what probably made you think it was 1sf? How do you know 300 was to 1sf? What if it had actually been 300.1 and hence it was rounded to 300 (3sf)? Or, as you say, it could have been 310 and it was rounded to 300 (1sf). The thing is, we can't tell.
AQA should have given 300 as 3.00 x 10^2-->because when using standard form, one can always tell what standard figures are being used. Would recommend that you give your answers in standard form, e.g.
Say you got an answer of 177200-->rather than writing 177000 to 3sf, it is better to write 1.77 x 10^5, because this makes it very clear without a doubt that you are indeed giving to 3sf.
^ This
20. (Original post by haes)
0.695???grams ??? but i rounded it to 0.7 because i assumed it was to 1.s.f
Me too, I got the same, but I have strong feeling we have may lost a mark by not writing 0.70g as most of the values were like that.

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