Year 12s: what will be the first way you research your future options? >>

AQA CHEM1: 15th May 2012

Scroll to see replies

Original post by Mike Hunt is nice

Have finished all the past papers and consistently have been getting between 56-62/70. Should i leave it now and revise for some of my later exams of should i carry on?

No carry on, like make last minute minda maps refresh your memory, take a break and get back, I do sound extreme but just sayin based on past experience :smile:

Reply 221

ambrin ox

Original post by joker12345

Still don't get why it's wrong to call it a simple covalent structure though :/ and scroll down on here http://web.aqa.org.uk/UMS/index.php and select the year etc, it tells you the raw mars - UMS conversions

well, think of it this way, by saying simple covelant, you only mention covalent bonding, whereas you have both covelant and van der waals bonding, so you need to say molecular, because its attraction between molecules,

Reply 222

juliewho

Original post by joker12345

Still don't get why it's wrong to call it a simple covalent structure though :/

It's not really technically wrong - I know my textbook refers to them as "simple covalent" and "giant covalent". It's another case of picky markschemes, but it's best to remember them as simple molecular and macromolecular to be safe.

Reply 223

AishaTara

Original post by Mike Hunt is nice

Have finished all the past papers and consistently have been getting between 56-62/70. Should i leave it now and revise for some of my later exams of should i carry on?

have a break for now, and maybe go over one or two things you forget before bed. My teachers say if you work too much, you can work yourself out, then blank out in the exam :/

Reply 224

chris_94

Original post by joker12345

Write an equation to show how NO is removed from the exhaust gases in a catalytic
converter. Identify a catalyst used in the converter.

Will they always allow all the different equations ie reacting with C/CO/decomposition?

2CO + 2NO --- 2CO2 + N2
OR

C8H18 + 25NO --- 8CO2 + 12.5 N2 + 9H2O
OR

C + 2NO --- CO2 + N2
OR

2NO --- N2 + O2

Pt/ Pd/ Rh/ Ir are the catalysts

(copied from the mark scheme)

Reply 225

4MANU4EVER4

Original post by AishaTara

have a break for now, and maybe go over one or two things you forget before bed. My teachers say if you work too much, you can work yourself out, then blank out in the exam :/

i don't think that is possible

Reply 226

ummy123

Original post by AishaTara

have a break for now, and maybe go over one or two things you forget before bed. My teachers say if you work too much, you can work yourself out, then blank out in the exam :/

thats not strictly true. it just depends how you work, how much you remember.
just work how you work best. :biggrin:

kill me now

Original post by 4MANU4EVER4

i don't think that is possible

It is. It happened to me in January.

Reply 229

dinosaretoocool

Original post by Erotas

Is it worth it or is anyone doing the papers from the past specification?

its worth it. the past specification questions tend to be harder therefore, if you prepare yourself for those questions you'll be fine for the exam... at least i hope! also, you can see which questions the examiners ask from year to year and secure those marks definitely in the real thing! :smile:

Reply 230

woohooo

ugh yes check this out:

(its june 2009)

1 (b) (ii) Explain why the second ionisation energy of sodium is greater than the second
ionisation energy of magnesium.

(3 marks)

idk if people find that easy or its just me but i wouldnt have got that in the exam.. when i read th q i got so confused but this is the mark scheme:

1st mark: Na(2+) requires loss of e- from a 2(p) orbital or2nd energy level or
2nd shell and Mg(2+) requires loss of e- from a 3(s) orbital or 3rd
energy level or 3rd shell / Na(2+) loses e from a lower (energy)
orbital/ or vice versa;

2nd mark: Less shielding (in Na);

3rd mark: e(-) closer to nucleus/ more attraction (of electron to nucleus) (in
Na)

it's basically just saying how Na is in group one so only has one electron in its outermost shell when it loses it's outermost electron, that whole shell is lost, so then to take another electron away (2nd ionisation energy) it requires more energy thannnnnn magnesium... cos magnesium is in group 2 and has 2 outermost electrons in its outermost shell, so when the first electron is removed, there's still another electron in the outermost shell so removing that one (the second ionisation energy) is minorrrr, doesnt take as much energy. so that's why SECOND ionisation energy of magnesium is lower than that of sodium. Oh then throw in how the 2nd last electron is closer to the nucleus in Na (cos of that lost shell)

...chayz

Reply 231

. . .

Original post by SHAH :)

how do you calculate relative formula mass?

That is just another word for relative molecular mass but is used for ionic compounds. You work it out the same way you work relative molecular mass out by adding the Ar.

Reply 232

AishaTara

Original post by dinosaretoocool

really? I find those ones easier :/

Reply 233

TaraBelle

one was about why fuel for camping is in liquid form rather than as a gas. It's not because it more safe or easier to store, oh no, it's cause it takes up less stupid volume!

Reply 234

rss.914

does anyone know how to answer this questions?..........

Sometimes the mass spectrum of Kr has a very small peak with an m/z value of 42
Explain the occurrence of this peak.

Reply 235

juliewho

Original post by rss.914

does anyone know how to answer this questions?..........

Sometimes the mass spectrum of Kr has a very small peak with an m/z value of 42
Explain the occurrence of this peak.

Sometimes in mass spec, atoms are ionised to form 2+ ions instead of 1+ ions. They have an M/Z value of mass/2 instead of mass/1, so are roughly half the mass value of the 1+ peaks.

Reply 236

ambrin ox

Original post by TaraBelle

one was about why fuel for camping is in liquid form rather than as a gas. It's not because it more safe or easier to store, oh no, it's cause it takes up less stupid volume!