[mathsclown]

(Original post by Bright)
I have almost convinced myself that enthalpy change of neutralisation will come up tomorrow..
I've forgotten how to do it using the graphs etc.. can someone explain please because it is not in the chem text book..

Off top of my head
Method:
- measure base by pippette and transfer to insulated cup with thermometer
- place acid in burette
- allow time for solutions to equilibrate
- add 5cm3 acid while stirring (work quickly to avoid heat loss)
- record temps. until you get several readings thaaat show a decrease - end point has been passed

Treatment of results: Plot temp vs vol graph
- graph looks like this /\, extrapolate/ extend the 2 lines the intersection is the endpoint
- work out deltaT from graph (temperature always increase as exo- reaction)
- get moles of water (limiting) by using endpoint
- for q=mcdT, mass is the volume of acid + volume of base
- sub values into deltaHn = q/neutMOLES, didvide by thousand and make sign -

[walkbesideme]

(Original post by DoctorVertigo)
How do we work out the concentration of a gas?

You would have to use partial pressures in the real world and Kp but this isn't on the OCR specification so you generally just get told that the gasses are held in a pressurised vessel which is held at a constant pressure eg: 2moldm-3 and from that you can just treat them as a liquid.

[Rahmeh.]

(Original post by DoctorVertigo)
I've just been thinking, you know when we work out equilibrium concentrations of gases do we use n=cv? I've suddenly got confused!

yes you use n=cv

[Dollyandra]

(Original post by mathsclown)
Off top of my head
Method:
- measure base by pippette and transfer to insulated cup with thermometer
- place acid in burette
- allow time for solutions to equilibrate
- add 5cm3 acid while stirring (work quickly to avoid heat loss)
- record temps. until you get several readings thaaat show a decrease - end point has been passed

Treatment of results: Plot temp vs vol graph
- graph looks like this /\, extrapolate/ extend the 2 lines the intersection is the endpoint
- work out deltaT from graph (temperature always increase as exo- reaction)
- get moles of water (limiting) by using endpoint
- for q=mcdT, mass is the volume of acid + volume of base
- sub values into deltaHn = q/neutMOLES, didvide by thousand and make sign -

you, Sir, are a boss.

[Theflyingbarney]

(Original post by DoctorVertigo)
How do we work out the concentration of a gas?

They'll give you a volume of a container and a number of moles, it's still mol/dm3.
Either that or they give you a volume of a gas and you just have to divide it down, remember 24dm3 = 1 mol of gas.

[Aa234]

(Original post by Stevo F)
me

How is your revision going for it?


This was posted from The Student Room's iPhone/iPad App

[Tyles]

(Original post by Aa234)
How is your revision going for it?


This was posted from The Student Room's iPhone/iPad App

wasting precious TSR megabytes on you're little revision convo for another exam on my F325 MEGA THREAD. HOW DARE YOU!>!>!!>

jussssst kidding xoxo

[Konshi]

Jun 2011, Q2cii, Kc Calculation. I've got the moles of NO2 and NO as 0.2 and 0.6, but why are mol of O2 0.4? I would've thought they are 0.3?

[Theflyingbarney]

(Original post by mathsclown)
Off top of my head
Method:
- measure base by pippette and transfer to insulated cup with thermometer
- place acid in burette
- allow time for solutions to equilibrate
- add 5cm3 acid while stirring (work quickly to avoid heat loss)
- record temps. until you get several readings thaaat show a decrease - end point has been passed

Treatment of results: Plot temp vs vol graph
- graph looks like this /\, extrapolate/ extend the 2 lines the intersection is the endpoint
- work out deltaT from graph (temperature always increase as exo- reaction)
- get moles of water (limiting) by using endpoint
- for q=mcdT, mass is the volume of acid + volume of base
- sub values into deltaHn = q/neutMOLES, didvide by thousand and make sign -

Oh crap, I'd forgotten that all of that was on the syllabus

*returns to textbook*

[:)?]

Yeah so, turns out I started revising today. Did a past paper and got an E. Am I delusional in thinking I'd be able to get this up to a high C by revising the content tonight? I understood everything when we did it, but haven't really looked at anything since about Easter. I hate myself right now, but can't do anything about it. Am I better off staying up until about 3 instead of getting a good night's sleep considering HOW FAR behind I am?

[AlphaOmega93]

We have to do Enthalpy Change of Neutralisation on a graph????

[Stevo F]

(Original post by Tyles)
wasting precious TSR megabytes on you're little revision convo for another exam on my F325 MEGA THREAD. HOW DARE YOU!>!>!!>

jussssst kidding xoxo

BRING IT!!! just kidding

[Tyles]

(Original post by Theflyingbarney)
Oh crap, I'd forgotten that all of that was on the syllabus

*returns to textbook*

i doubt they'll ask that tbf

[dcpower]

can anyone tell me why do you have to do moles x 40 to get concentration i saw this two times in markscheme. i thought to workout concentration its c = n/V

[walkbesideme]

If only I could read =_=

[Petro_99]

(Original post by AlphaOmega93)
We have to do Enthalpy Change of Neutralisation on a graph????

never heard of that before???

[Stevo F]

(Original post by Aa234)
How is your revision going for it?


This was posted from The Student Room's iPhone/iPad App

havent done THAT much tbh, got lots of exams but I can do most of it without revision, will revise a lot this weekend, should be enough hopefully

[ILikeToEat]

Already asked this, but can someone please help me with question 6(d) of the specimen paper? I'm dying!

[Tyles]

(Original post by dcpower)
can anyone tell me why do you have to do moles x 40 to get concentration i saw this two times in markscheme. i thought to workout concentration its c = n/V

there is 2 triangles.

n = c x v
also there is v = n x 24dm^3 for gasses.

[mathsclown]

(Original post by Theflyingbarney)
Oh crap, I'd forgotten that all of that was on the syllabus

*returns to textbook*

No idea what's in the text book and what isnt, my teacher made notes for my class for whole syllabus so just memorised and used them.