****Leaving Certificate Chemistry [All Levels] Before and After Discussion****

Apocladagr0

rainbowtrout wrote: »

The question asks how many moles of nitrogen gas so 0.9 moles.

But it would be 0.2 moles if it asked for how many moles of NO at equilibrium

ARGH misread the question as usual, you're completely right.

What did everyone say for 2(d) ?

most of the NaOH surely would be in the brine by Stage 4?
Was the thorough washing just to remove any NaOH that was still in the soap?
I said to wash it with ethanol, think it's wrong but I didn't want to say to use water or else the yield would lather away, which would also be wrong

For 5(c) Was the additional experimental evidence atomic absorption or emission? Never really thought about it before, suddenly hit me in the exam both mightn't be acceptable:rolleyes:

rainbowtrout

Yulkmn wrote: »

you'll still get nearly full marks.
I did :
at equilibrium 2x = 1-x 1-x
then put it in and equaled it to 21 ( or what ever the kc was)
then I went on and did the -b formula
and got x to be 0.025 and 47 I disregarded the 47 and took the 0.025 and got 1-0.025 and which is .975.
anybody think I'll get any marks for that?

Using 2x and 1-x I still get the same answer for N gas = 0.9 moles

I find the -b formula too cumbersome, easier to square root both sides. Usually works out fairly neatly


But I've done it out both ways, and the answer is still 0.9

Yulkmn

rainbowtrout wrote: »

Using 2x and 1-x I still get the same answer for N gas = 0.9 moles

I find the -b formula too cumbersome, easier to square root both sides. Usually works out fairly neatly


But I've done it out both ways, and the answer is still 0.9

aghh I did all that however at the start where there is a 2x^2 when I brought it over the equals I forgot the ^2 and just multiplied by 2x but I did. everything else the same way.. what would be the marks like?

rainbowtrout

Yulkmn wrote: »

aghh I did all that however at the start where there is a 2x^2 when I brought it over the equals I forgot the ^2 and just multiplied by 2x but I did. everything else the same way.. what would be the marks like?

Impossible to say until the scheme comes out in August to be honest.

Yulkmn

rainbowtrout wrote: »

Impossible to say until the scheme comes out in August to be honest.

but do you think tho cause my enitre method is right except one little error which makes my calculation wrong i think i would get 6-9 marks out of 12 as all was right except final answer.

chatterboxxx95

booblefoop wrote: »

Is it that it had been made up to a solution of known concentration? That was a weird one, they usually ask what a primary standard is

I think, now I could be very wrong here, that it a soultion of precisely known concentration, not been made up, as HCL is not a primary standard, therefore you cannot know its exact concentration unless you carry out an experiment.

Yulkmn

chatterboxxx95 wrote: »

I think, now I could be very wrong here, that it a soultion of precisely known concentration, not been made up, as HCL is not a primary standard, therefore you cannot know its exact concentration unless you carry out an experiment.

it has previouslty been titrtrated to obtain a solution of accuretly know concentration

Apocladagr0

Yulkmn wrote: »

it has previouslty been titrtrated to obtain a solution of accuretly know concentration

Do you think there will be marks going for 'previously titrated'?
You can make a std solution using a primary standard, no titration needed.

jellytots95

What did people get for the beta emmission equation thing in question 4

Inspector Coptoor

223Fr87 --> 223Ra88 + 0e-1 + energy

rainbowtrout

jellytots95 wrote: »

What did people get for the beta emmission equation thing in question 4

Should turn into radium Ra 223,88 plus an electron. Awkward to write out here.

rainbowtrout

On a lighter note, were the SEC having the craic when they put a picture of Heisenberg in a hat on the paper, letting everyone know they have seen Breaking Bad?

Peter Flynt

rainbowtrout wrote: »

On a lighter note, were the SEC having the craic when they put a picture of Heisenberg in a hat on the paper, letting everyone know they have seen Breaking Bad?

I was thinking that myself.

Indeed what chance Bryan Cranston appearing on next year's paper?

kev44

Crap! For the equilibrium i said 2- x instead of 2-2x...the maths was all done perfectly just the initial mistake...might get some marks

CiaraMT

kev44 wrote: »

Crap! For the equilibrium i said 2- x instead of 2-2x...the maths was all done perfectly just the initial mistake...might get some marks

Did the exact same thing as you. I'm hoping the same thing

Gabrielazap

Just wondering what u guys said for q2 describing the relationship between temp and rate and exlain ur answer?:):)

Gabrielazap

U will probably get a good chunk of the marks for the correct method:) that is if all the maths is correct!;)

robman60

That was a very nice paper really!

I did seven good questions and then the pH one screwed me pretty badly. I had to do it though because I couldn't do much with the three I left.

For Q5 was the scientist Neils Bohr and the other proof for energy levels light emission spectra?

Gabrielazap

Yeah, I got the same:) what points did u mention for why silicon has a higher/lower first ionization energy value than aluminium and carbon respectively?:)

Just wondering what answers yee all put for the last 2 parts in q5:)

AtomicKoala

Actually, will I lose marks for writing "Bohr, Neils Bohr"?

I was going to cross out the first Bohr after remembering his full name, but I thought it was quite amusing that way :pac:

booblefoop

AtomicKoala wrote: »

Actually, will I lose marks for writing "Bohr, Neils Bohr"?

I was going to cross out the first Bohr after remembering his full name, but I thought it was quite amusing that way :pac:

There's 0 chance an examiner would take marks off for that :P

EoghanIRL

Gabrielazap wrote: »

Just wondering what answers yee all put for the last 2 parts in q5:)

I think I said something about more energy being required to remove an electron from a new shell. Can't remember exactly how I phrased it now .


The last part I said that a line spectrum is evidence . Not sure if that's right or not though I just guessed

Gabrielazap

EoghanIRL wrote: »

I think I said something about more energy being required to remove an electron from a new shell. Can't remember exactly how I phrased it now .


The last part I said that a line spectrum is evidence . Not sure if that's right or not though I just guessed

Thanks:) yeah I said about the same

Gabrielazap wrote: »

Thanks:) yeah I said about the same

By any chance do u remember roughly what you said for why silicon has a Lowe first ionization energy value than carbon?;)

Gabrielazap wrote: »

By any chance do u remember roughly what you said for why silicon has a Lowe first ionization energy value than carbon?;)

* lower

EoghanIRL

Gabrielazap wrote: »

Thanks:) yeah I said about the same

Q3 (f) is the answer that the rate of reaction is decreased by 1/2 because sodium thiosulfate is the limiting reagent and rate of reaction is affected by concentration ?

Q2(g) I said that c17h35 part of molecule is non polar and the coo Na part is polar and that like dissolves like. I.e polar dissolves polar

Finally last part of 11(a)
I said that the centre of gravity of the negative charge coincides with the centre of gravity of the positive charge .

These ones were bugging me .

Gabrielazap wrote: »

* lower

I think I said that silicon has a greater atomic radius than carbon so electrons are further away from nucleus . Requires less energy to remove them. Not sure if this is what they wanted .

Gabrielazap

EoghanIRL wrote: »

I think I said that silicon has a greater atomic radius than carbon so electrons are further away from nucleus . Requires less energy to remove them. Not sure if this is what they wanted .

I said the same:) thanks;)

what did u say for q3 part d?;)

Does anyone Remember what they said for q3 part d it was describe and explain the relationship of the graph

larkinitis

Probably passed it, but I hated chemistry!

Why do schools make you do a science subject when you have no interest in it?!

rainbowtrout

larkinitis wrote: »

Probably passed it, but I hated chemistry!

Why do schools make you do a science subject when you have no interest in it?!

That's the school's individual policy. Science subjects are not compulsory for the Leaving Cert.

plmko

larkinitis wrote: »

Probably passed it, but I hated chemistry!

Why do schools make you do a science subject when you have no interest in it?!

Not all schools do that? That's horrible!

Wanderer41

I think I did the equilibrium question wrong as well I don't know how I did it wrong, after all the questions I had practised I would have to make a mistake in the exam

Caolan

larkinitis wrote: »

Probably passed it, but I hated chemistry!

Why do schools make you do a science subject when you have no interest in it?!

Same reason they make you do a foreign language - most of the 3rd level courses demand a science and european language (not all)

it doesnt make sense when your 17/18 and are focused on something that doesnt need it- but as someone who didnt do a science at LC- it closes alot of doors later in life should you wish to apply for many courses.