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

MacBizzle

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

Yeah that's it

Yulkmn

anyone know for the rates if u put the time on the bottom and temperature on the side if that's okey ??

mirrors

Yulkmn wrote: »

anyone know for the rates if u put the time on the bottom and temperature on the side if that's okey ??

No I'd say you'd lose a few marks

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

A solution with a known concentration

MacBizzle

Yulkmn wrote: »

anyone know for the rates if u put the time on the bottom and temperature on the side if that's okey ??

Wasn't it rate not time?

Yulkmn

MacBizzle wrote: »

Wasn't it rate not time?

it was 1/t
I put it on the x axis and put temperature on the y axis

MacBizzle

Yulkmn wrote: »

it was 1/t
I put it on the x axis and put temperature on the y axis

I think that's the right way, well that's what everyone in my class did. I did it the other way though and am nearly sure it's wrong :rolleyes:

TooMuchStudy

MacBizzle wrote: »

I think that's the right way, well that's what everyone in my class did. I did it the other way though and am nearly sure it's wrong :rolleyes:

is it not the value you set on the x-axis and the variable on the y-axis?

Peter Flynt

Everytime the world cup is on . . Soap appears - 2002, 2006, 2010, 2014. .

Yulkmn

TooMuchStudy wrote: »

is it not the value you set on the x-axis and the variable on the y-axis?

yeah the variable is the temp isn't it?
and did u get something like 66 seconds for the next part?

randylonghorn

Peter Flynt wrote: »

Everytime the world cup is on . . Soap appears - 2002, 2006, 2010, 2014. .

And in real life it's usually a conflict between the World Cup and the soaps in a lot of houses ... :pac:

MacBizzle

Yulkmn wrote: »

yeah the variable is the temp isn't it?
and did u get something like 66 seconds for the next part?

Did your graph start off steep and then get less steep or did it get steeper as it went on?

Apocladagr0

PhysicsKid99 wrote: »

What was the proper definition for standardised too, actually?

And what did people say for butane/propane differences? I said higher molecular mass and stronger Van der Waals forces for butane, was that right?

For standardised I said ' a soln. of precisely known concentration '.
I vaguely remember being told to be more detailed in a class test for that question but I couldn't remember what else to write:rolleyes:

I said more v.d.w. for butane too. I knew it was a six marker so they would probably be expecting two points but I couldn't think of another:o

Also for equilirium my x came out to be 0.9
So the #mol N2 at equil = 2-2x = 0.2 mol. ??

Inspector Coptoor

A very rough sketch of Q3
And the graph of rate vs temp.



For the butane vs propane question.
Id be saying higher Mr means more bonds meaning increased vdw forces which raises the bp

MacBizzle

Inspector Coptoor wrote: »

And the graph of rate vs temp.

That's the right way!?!

brian888

MacBizzle wrote: »

That's the right way!?!

could've fcuking sworn it was the opposite way round on the axes. Ah well, I only need a D3 anyways!

Yulkmn

MacBizzle wrote: »

That's the right way!?!

I put it as 1/t to be x-axis and it came out different like it went upwards from xaxis and kinda to the right in a curve

like I don't think you would lose a lot of marks if u did it the other way, cause it only said time vs temp

Peter Flynt

Since you're on the topic. . .

brian888

You sir, make me sad.

Yulkmn

Peter Flynt wrote: »

Since you're on the topic. . .

can you make one with the axis' switched around?

Inspector Coptoor

You could.
But it would be wrong

Yulkmn

Inspector Coptoor wrote: »

You could.
But it would be wrong

how tho? it just switching the axises

rainbowtrout

EoghanIRL wrote: »

Could you do the equilibrium calculation and see what answer you get . It would be great if you had time . I haven't seen the answer anywhere on here yet .

Chem equilibrium Q9

Inspector Coptoor

It would change the shape of the graph and tell an examiner the candidate didnt know a dependent variable from an independent variable

Peter Flynt

If you got the axes the wrong way around . . . Don't panic

In 2002 for the same experiment (although with rate against concentration rather than temperature) it stated this directly from the marking scheme.



See it there. . . "Rate can be on horizontal or vertical axis; similarly for concentration"

Inspector Coptoor

Talk about hand holding.
Who's doing the exam?
The candidates or the examiners?

That's like saying 2 + 2 = 4
Or 5

Yulkmn

Peter Flynt wrote: »

If you got the axes the wrong way around . . . Don't panic

In 2002 for the same experiment (although with rate against concentration rather than temperature) it stated this directly from the marking scheme.]

See it there. . . "Rate can be on horizontal or vertical axis; similarly for concentration"

thank you pheeeew do you know if there's attempt marks for the questions such as the equillbrium and the last part in Q1 the finding the value X ??

yoajing

Isn't brine needed to precipitate the soap?

Apocladagr0

rainbowtrout wrote: »

Chem equilibrium Q9

Don't you have to do 2-2x though, so final answer is 0.2 mol. ?

rainbowtrout

Apocladagr0 wrote: »

Don't you have to do 2-2x though, so final answer is 0.2 mol. ?

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

Yulkmn

Apocladagr0 wrote: »

Don't you have to do 2-2x though, so final answer is 0.2 mol. ?

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?

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: