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WJEC AS Chemistry CH1 May 22nd 2015

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Original post by Mr Bill
You sound a bit sodium chloride, is this smart white people jokes?

NaCl is the chemical formula for salt,
He was saying he was salty or in simpler terms he was mad
Original post by Formless
NaCl is the chemical formula for salt,
He was saying he was salty or in simpler terms he was mad


Yeah he's gonna be callin me coordination number 6:6 soon
Few of My answers that i can remember, not completely correct, NOT in order of questions (sorry) Feel free to add or improve. id appreciate if you rep this post if it helps

1.

Halftime - The time taken for the radioactivity of a specified isotope to fall to half its original value.

2.

Oxygen2- has 8 protons, 10 neutrons, 10 electrons

3.

226Ra decays into 222Rn

4.

Moles = 0.0111

5.

-417kJ/mol

6.

(gmol-1) gram per mole or, Mass of one mole of a compound

7.

x = 4 for the H20

8.

Ionisation energy is the energy required to remove one mole of electrons from one mole of its gaseous atoms

9.

Phosphorus has a higher ionisation energy than sulphur as sulphur has an electron paired in a sub orbital resulting in repulsion thus easier to remove.

10.

Magnesiums 2nd ionisation energy is a lot higher as nuclear charge is increased and sue to electron - electron repulsion

11.

Suggest a value for the IE - 1000???

12.

Lithium is ionised in mass spectrometer through an electron gun, The atom or molecule is ionised by knocking one or more electrons off to give a positive ion.

13.

Lithium RAM = 6.93

14.

Lithium7 and Lithium6 have the same chemical properties due to same electron number

15.

Lower m/z are deflected more thus Li6 is deflected more due to lower mass (one less neutron)

16.

Ef-Eb =deltaH

17.

Empirical formula for NO is N205

18.

0.32dm^3 volume of gas

19.

Atom economy 18.9/18.8/19%

20.

-36.6KJmol?

21.

Yield of NO Decreases as pressure increases, Thus Products have more moles

22.

Yield of NO Decreases as temperature increases, Exothermic reaction

23.

900C is used as although a lower temperature can result in more yield, higher temperature = faster rate of reaction

24.

Pipette to measure 25cm3 of solution

25.

Heat loss to surroundings result in experimental errors an thus different enthalpy values

26.

Zac could insulate the calorimeter

(edited 8 years ago)
Original post by Jack1066
The follow up questions rely on a previous answer so I think we should get error carried forward


I really don't like that because when I realised that my temp. change was wrong there was nowhere near enough time to correct all my calculations that depended on that one answer... I hate WJEC sometimes...
Original post by VeepFan
spent about 20 minutes finding x, it went from 1 to 9 to 0.1 and i settled on 9. i know its wrong


Well to be fair x has to be an integer. And probably a relatively low integer. And very unlikely to be 1. Oh well, most people messed up somewhere! (Including me in a few too many places. :angry:)
Original post by Formless
Few of My answers that i can remember, not completely correct, NOT in order of questions (sorry) Feel free to add or improve. id appreciate if you rep this post if it helps

1.

Halftime - The time taken for the radioactivity of a specified isotope to fall to half its original value.

2.

Oxygen2- has 8 protons, 10 neutrons, 10 electrons

3.

226Ra decays into 222Rn

4.

Moles = 0.0111

5.

-417kJ/mol

6.

(gmol-1) gram per mole or, Mass of one mole of a compound

7.

x = 4 for the H20

8.

Ionisation energy is the energy required to remove one mole of electrons from one mole of its gaseous atoms

9.

Phosphorus has a higher ionisation energy than sulphur as sulphur has an electron paired in a sub orbital resulting in repulsion thus easier to remove.

10.

Magnesiums 2nd ionisation energy is a lot higher as nuclear charge is increased and sue to electron - electron repulsion

11.

Suggest a value for the IE - 1000???

12.

Lithium is ionised in mass spectrometer through an electron gun, The atom or molecule is ionised by knocking one or more electrons off to give a positive ion.

13.

Lithium RAM = 6.93

14.

Lithium7 and Lithium6 have the same chemical properties due to same electron number

15.

Lower m/z are deflected more thus Li6 is deflected more due to lower mass (one less neutron)

16.

Ef-Eb =deltaH

17.

Empirical formula for NO is N2050.

18.

32dm^3 volume of gas

19.

Atom economy 18.9/18.8/19%

20.

-36.6KJmol?

21.

Yield of NO Decreases as pressure increases, Thus Products have more moles

22.

Yield of NO Decreases as temperature increases, Exothermic reaction

23.

900C is used as although a lower temperature can result in more yield, higher temperature = faster rate of reaction

24.

Pipette to measure 25cm3 of solution

25.

Heat loss to surroundings result in experimental errors an thus different enthalpy values

26.

Zac could insulate the calorimeter



I can't remember some of the value questions, but I think yours are mostly correct.

Comments:

The nuclear charge of magnesium doesn't increase after first ionisation.

Definitely not 1000 for IE. I put 7800 since there had to be a large increase.

Not one or more electrons. Note that this would mess up the whole mass/charge ratio deflection business. They all have to be 1+ ions and that was the answer I gave to why only the minimum energy was used to ionise them.

Looking back, "chemical properties" was ridiculously vague. I just assumed (for some reason) that they were asking about atomic configuration, so I talked about number of each nucleon and electrons. I'm not sure why they thought that was a good way to phrase the question. Technically, you could talk about melting points or something and still deserve the marks...

I put Ef-Eb BEFORE drawing the diagram, thinking "I just read in my notes this morning that deltaH is Ef-Eb; I'm so happy I read the spec. last minute). Then I drew out the diagram, saw that Ef was larger than Eb and changed it. Then after the exam I realised that deltaH was negative BECAUSE the larger energy was taken away from the smaller energy. So you're right there, and I screwed up on an easy question that I had just learnt the answer to...

I got -50 for the enthalpy change, although I'm not sure how much of an effect a different deltaT would have on that value.

Apart from those points, I agree with your answers. :biggrin:
Reply 206
Avatar for Ser_
Ser_
6
Original post by VeepFan
spent about 20 minutes finding x, it went from 1 to 9 to 0.1 and i settled on 9. i know its wrong


I got 9 too, you're not alone :wink:


Posted from TSR Mobile
Original post by PrimeLime
I can't remember some of the value questions, but I think yours are mostly correct.

Comments:

The nuclear charge of magnesium doesn't increase after first ionisation.

Definitely not 1000 for IE. I put 7800 since there had to be a large increase.

Not one or more electrons. Note that this would mess up the whole mass/charge ratio deflection business. They all have to be 1+ ions and that was the answer I gave to why only the minimum energy was used to ionise them.

Looking back, "chemical properties" was ridiculously vague. I just assumed (for some reason) that they were asking about atomic configuration, so I talked about number of each nucleon and electrons. I'm not sure why they thought that was a good way to phrase the question. Technically, you could talk about melting points or something and still deserve the marks...

I put Ef-Eb BEFORE drawing the diagram, thinking "I just read in my notes this morning that deltaH is Ef-Eb; I'm so happy I read the spec. last minute). Then I drew out the diagram, saw that Ef was larger than Eb and changed it. Then after the exam I realised that deltaH was negative BECAUSE the larger energy was taken away from the smaller energy. So you're right there, and I screwed up on an easy question that I had just learnt the answer to...

I got -50 for the enthalpy change, although I'm not sure how much of an effect a different deltaT would have on that value.

Apart from those points, I agree with your answers. :biggrin:

Regarding the ionisation energy suggestion, Cant remember what i put for that, It was either
in between 7000 and 13000 so i meant to put 10000, either that or it was
BLANK, 10000 13000, Than i put 7000 closer to yours
(edited 8 years ago)
Original post by Formless
Regarding the ionisation energy suggestion, Cant remember what i put for that, It was either
in between 7000 and 13000 so i meant to put 10000, either that or it was
BLANK, 10000 13000, Than i put 7000 closer to yours


Yeah it was sort of like 700, 1000, blank, 10000, 13000 (approx.) so I thought roughly 7800 would be accurate since it should steadily increase after that.
Reply 209
Avatar for Ser_
Ser_
6
What did you guys put for the QWC question on renewable fuels? I thought it was a bit random?
Reply 210
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Ben_14
2
Original post by Ser_
What did you guys put for the QWC question on renewable fuels? I thought it was a bit random?

Entirely feasible, many different available forms of renewable energies, such as biofuels- cars, Wind farms to generate clean electricity, the use of catalyst to generate better yields of products with the reduction of temperature and pressure.
Along this lines, gotta be worth at least two marks I guess.
Original post by Sh4hid96
Overall I thought it was a difficult paper. They done things in this paper which haven't been done before. Like the way for example, they presented the equilibrium question, or that last page which completely surprised me, as it was like no other graph I've seen before. Also, the calculations throughout were tricky, so I think the grade boundaries will be lower than last year. Thats just my opinion, but I did think that it was a difficult paper.


Thank god someone else is thinking like I am! I thought it was really tricky; all of the calculations, even though most were only 3 mark questions, had some sort of tricky bit in them to get the right answer! The equilibrium question took me a while - I actually had to draw it out in pencil so understand what was happening! I'm guessing low boundaries too, asnearly everyone seems to have messed at some points of the exam, so it's not like there was just 1 difficult question.

I got 18 for x; so god knows what I did!
Original post by Mr Bill
Yeah he's gonna be callin me coordination number 6:6 soon


You sound coordination number 6:6 Mr Bill, I'm worried about you.
Original post by PrimeLime
Yeah it was sort of like 700, 1000, blank, 10000, 13000 (approx.) so I thought roughly 7800 would be accurate since it should steadily increase after that.


Yeah I put 8000. So it was a significant increase from 2nd ionisation energy, but still below the 4th.
Ngl, walked out of all my exams (except C1) extremely confident, only to come on TSR and have that confidence shattered. :confused:
Original post by Jack1066
Yeah I put 8000. So it was a significant increase from 2nd ionisation energy, but still below the 4th.


yeah i put 8500
Reply 216
Avatar for HG_07
HG_07
3
Can anyone remember how many marks the first alpha radiation question was worth and how many marks the calculation of the half life was?
Original post by VeepFan
yeah i put 8500


What did everyone write for define molar 1st ionisation energy? I was going to write about standard conditions but it didn't say standard molar...
Reply 218
Avatar for HG_07
HG_07
3
Original post by Questioner1234
What did everyone write for define molar 1st ionisation energy? I was going to write about standard conditions but it didn't say standard molar...

The energy required for one mole of electrons to be removed from one mole of is gaseous state (or atoms)
Can't remember if I put state or atoms :/
Original post by Faisalshamallakh
Ngl, walked out of all my exams (except C1) extremely confident, only to come on TSR and have that confidence shattered. :confused:


And that's why everyone loves TSR! :h:
But seriously, TSR is not for the faint-hearted XD.
What did you find hard about (I'm assuming WJEC) C1? How did C2 go?

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