PDA

View Full Version : Any chemists? I need some help with simple mole calculations.

!<blocparty>!
Mar 21st, 2006, 08:52 PM
:tape:

OK, so I have this practical tomorrow but aren't 100% sure on a couple of things. I need to get a pretty high A, or else I'm fucked.

http://img.photobucket.com/albums/v697/bloc_party/chem.jpg

So anyway, the first one seems OK, you just do

5.200 (the mass I used) X1000 / 204.2 X 250... right? (I'm not sure of the units, though.

For 2, you need the molar concentration. Now, the formula we use to get concentration is moles/volume in dm cubed. BUT... I don't know what the moles are. Are the MOLES what I had for the first question? If so, I could do:

*moles in first question*/ volume (which was an average of 23.35cm3)/1000

= mol dm-3

and for question 3 it would just be the same as question 2 but with my second volume from titration 2 (which was 25.35cm3)

I think thats right... but I'm not sure if the concentration for the first question is the same as the moles. I have no other way of working out the moles for the C= N/V thing. :confused:

I hope you're following me. :p

So basically I just want to know how to work out the second question. Someone else suggested it could be... moles of KHP= molar concentravion X the titation volume (23.35) / 1000. Thus, that is the moles of NaOH, so, concentration NaOH would = moles/volume of NaOH (25cm3)/1000.

It's so stupid but I need to get it right.

RainyDays
Mar 21st, 2006, 10:21 PM
oh man i wish i could help; i'm "supposedly" taking a high chem class right now at school, but your paper is like a foreign languages to me. sorry.
you're probably more advanced in chem than i will ever be though.

angele87
Mar 21st, 2006, 10:38 PM
I'm not a chemist by any means ( still a uni student) but I might be able to help with some of it. What level chem is this btw? I don't want to totally screw you up if you're working on something way over my head.

decemberlove
Mar 21st, 2006, 10:40 PM
I haven't taken a chem class in 7 years, so I can't help you.

But is that Tim handwriting I see? How cute. :inlove:

angele87
Mar 21st, 2006, 10:58 PM
I'm not sure about the equation you're given in question 1, but here's how I would find the molar concentration:

Take the amount of grams you have and multiply it by 1 mol over the molar mass, that will give you mols. In any of the chem courses I've taken, molar concentration has been mols/L so if that's how you should find it, divide the mols by 0.250L which is what you put the 5g into. If you have to use cm^3, divide by 250 and if you have to use dm^3, just convert the cm^3 into dm^3 and divide by that.

For question 2, just remember that the mols of NaOH used to neutralize the solution is the same amount of mols in KHP in the solution. You already know the amount of mols of NaOH because you already found the mols of KHP. To find the molar concentration, do it the same way as question 1. For the volume, use the amount needed to neutralize the solution.

Question 3 is done much the same way as question 2.

Question 4 is a bit tricky but if you need help with that too, I could probably help you out. Hope what I said above makes sense... I'm just a little confused because I've never seen or used the equation in question 1.

!<blocparty>!
Mar 22nd, 2006, 07:37 AM
oh man i wish i could help; i'm "supposedly" taking a high chem class right now at school, but your paper is like a foreign languages to me. sorry.
you're probably more advanced in chem than i will ever be though.

US system. :tape:

:p

!<blocparty>!
Mar 22nd, 2006, 07:38 AM
I'm not a chemist by any means ( still a uni student) but I might be able to help with some of it. What level chem is this btw? I don't want to totally screw you up if you're working on something way over my head.

It's A-level. I'm guessing you're from the US... it's basically what people do here aged 17/18.

!<blocparty>!
Mar 22nd, 2006, 07:38 AM
I haven't taken a chem class in 7 years, so I can't help you.

But is that Tim handwriting I see? How cute. :inlove:

That's messy handwriting. I have poor handwriting at the best of times.

!<blocparty>!
Mar 22nd, 2006, 07:41 AM
I'm not sure about the equation you're given in question 1, but here's how I would find the molar concentration:

Take the amount of grams you have and multiply it by 1 mol over the molar mass, that will give you mols. In any of the chem courses I've taken, molar concentration has been mols/L so if that's how you should find it, divide the mols by 0.250L which is what you put the 5g into. If you have to use cm^3, divide by 250 and if you have to use dm^3, just convert the cm^3 into dm^3 and divide by that.

For question 2, just remember that the mols of NaOH used to neutralize the solution is the same amount of mols in KHP in the solution. You already know the amount of mols of NaOH because you already found the mols of KHP. To find the molar concentration, do it the same way as question 1. For the volume, use the amount needed to neutralize the solution.

Question 3 is done much the same way as question 2.

Question 4 is a bit tricky but if you need help with that too, I could probably help you out. Hope what I said above makes sense... I'm just a little confused because I've never seen or used the equation in question 1.

Hmmm.... well it's just question one. It tells you how to do it with the formula, I don't understand the way you worked it out, it's nothing I've ever come across before.

I just want to know... when you've worked out the concentration for question one, is that also the MOLES of KHP, or, to get the moles, do you use the equasion:

concentration= moles/volume?

THEN you have the moles of NaOH, too, so use

concentration= moles/volume.

It's just this bit.

Question 4 is fine.

I'll do both my calculations so you can see what I've got.

!<blocparty>!
Mar 22nd, 2006, 07:47 AM
http://img.photobucket.com/albums/v697/bloc_party/chem2.jpg

PamShriverRockz
Mar 22nd, 2006, 07:50 AM
Bloody hell Tim, I wish I could help...!!! But I know everything about nothing, so anything useful is too difficult to me! Good luck though :kiss:

!<blocparty>!
Mar 22nd, 2006, 07:54 AM
Bloody hell Tim, I wish I could help...!!! But I know everything about nothing, so anything useful is too difficult to me! Good luck though :kiss:

Blah. You got my hopes up then. :ras::sad:

Thanks anyway. :wavey:

!<blocparty>!
Mar 22nd, 2006, 01:16 PM
Bump. :awww:

No Name Face
Mar 22nd, 2006, 02:11 PM
not ignoring it, tim --- but this does not ring a bell.

:o

!<blocparty>!
Mar 22nd, 2006, 02:19 PM
not ignoring it, tim --- but this does not ring a bell.

:o

No Name Face
Mar 22nd, 2006, 02:21 PM

i know...i didn't get that
and i don't get titration :o :o

alfonsojose
Mar 22nd, 2006, 02:22 PM
It looks :scared: I'm going to report u to CIA :p

Good Luck

Grachka
Mar 22nd, 2006, 02:33 PM
Well, of course, I DO know the answers. I just choose not to divulge it.

:tape:

smiler
Mar 22nd, 2006, 02:46 PM
I'd love to help but I only got a D at chemistry A level & I don't wanna tell you how to do it wrong! Good luck with it mate! :wavey:

It's comforting to realise that 4 years on n=cv still rings a bell though!

MisterQ
Mar 22nd, 2006, 03:03 PM

Good luck on your exam. :)

Craigy
Mar 22nd, 2006, 03:05 PM
chemistry :tape: My teacher says I can get an A. Yeah sure I can when I don't have a clue about it :)

katiektc
Mar 22nd, 2006, 03:12 PM
Wow it's amazing how quickly you forget things! :eek: :o

I got 490/500 in my A-Level Chemistry exams, that was only 2 years ago, and I cannot for the life of me remember how to do any of this when I used to be able to do it off the top of my head.

Everytime I learn something new, it pushes some old stuff out of my brain ;)

Hope the exam went well though, Tim! :)

Avid Merrion
Mar 22nd, 2006, 03:44 PM
sorry Tim, i've no idea what you're on about but i've been dying to do this since you posted this thread. apologies in advance :lol:

http://www.uksafari.com/postcard/pictures/mole.jpg moley, mole, mole! :hearts:

hope you got on ok :)

!<blocparty>!
Mar 22nd, 2006, 03:58 PM
OMG.

:rolleyes: & :lol: @ the people who've posted bar Katie. You fools. :p I was like... wow 22 replies, SOMEONE has the answer!

!<blocparty>!
Mar 22nd, 2006, 04:01 PM
Wow it's amazing how quickly you forget things! :eek: :o

I got 490/500 in my A-Level Chemistry exams, that was only 2 years ago, and I cannot for the life of me remember how to do any of this when I used to be able to do it off the top of my head.

Everytime I learn something new, it pushes some old stuff out of my brain ;)

Hope the exam went well though, Tim! :)

Wow! Amazing marks. :worship:

I was actually meant to do it today but avoided the teacher in hope someone would tell me which one of my methods was correct. :p I'm pretty sure the second one is OK, though. It looks better than the first.

One random thing... do you remember if you can have a conecentration above 1.0? :tape::o

!<blocparty>!
Mar 22nd, 2006, 04:03 PM
sorry Tim, i've no idea what you're on about but i've been dying to do this since you posted this thread. apologies in advance :lol:

http://www.uksafari.com/postcard/pictures/mole.jpg moley, mole, mole! :hearts:

hope you got on ok :)

:lol: Maybe I should draw a mole in my exam and hope the examiner will give me marks for originality. :scratch:

:ras:

Avid Merrion
Mar 22nd, 2006, 04:06 PM
:lol: Maybe I should draw a mole in my exam and hope the examiner will give me marks for originality. :scratch:

:ras:
:lol: it might be worth a try ;)
and i am sorry, but you know you'd have done the same :ras:

Yasmine
Mar 22nd, 2006, 04:06 PM
I could have a look at it for you, have you managed it yet? :shrug:

!<blocparty>!
Mar 22nd, 2006, 04:08 PM
I could have a look at it for you, have you managed it yet? :shrug:

Check posts 1 and 10... tell me which method you would use out of the two in post 10. :)

LeRoy.
Mar 22nd, 2006, 04:14 PM
I'll give this a try

For 2 , you need a titration reading (amount of knowm molar of KHP solution needed to neutralize the X molar NaOH solution

1 --> KHP
2---> NaOH

Since 1 mol KHP is equivalent to 1 mol NaOH

N1 * V1 = N2*V2

where N = concentration V = volume

You know N1 from part (1) V1 would be the titration reading at which there was a color change from colorless to pink (i guess). You know V2 = 25 cm3

Hence N2= N1*V1/25
If you use V1 in cm3, N2 will have same units as N1

!<blocparty>!
Mar 22nd, 2006, 04:18 PM
I'll give this a try

For 2 , you need a titration reading (amount of knowm molar of KHP solution needed to neutralize the X molar NaOH solution

1 --> KHP
2---> NaOH

Since 1 mol KHP is equivalent to 1 mol NaOH

N1 * V1 = N2*V2

where N = concentration V = volume

You know N1 from part (1) V1 would be the titration reading at which there was a color change from colorless to pink (i guess). You know V2 = 25 cm3

Hence N2= N1*V1/25
If you use V1 in cm3, N2 will have same units as N1

Right... so basically, what you worked out in question one, needs to be multiplied by the volume to get the moles?

So, the moles of KHP = moles NaOH. So concentration NaOH would be Moles KHP/volume?

I think that's what you said but our formula's are different.

LeRoy.
Mar 22nd, 2006, 04:19 PM
For part 3

Now that the standardization is done you can use this NaOH to find molarity of another unkown acid HX

Do the titration and get a reading

let 1 --> NaOH , 2--> HX

Use N1*V1 = N2*V2 (since HX would still have 1 equivalent of H )

where N1 is the answer of part (2) , V1 is the titre value and V2 is the volume of acid you titrated against. Calculate N2 , conc of acid .

angele87
Mar 22nd, 2006, 04:20 PM
Hmmm.... well it's just question one. It tells you how to do it with the formula, I don't understand the way you worked it out, it's nothing I've ever come across before.

I just want to know... when you've worked out the concentration for question one, is that also the MOLES of KHP, or, to get the moles, do you use the equasion:

I'm from Canada but I imagine the methods here are the same as the method in the US. The concentration will be the mols/V so you should just have to multiply the concentration by your volume to get mols alone. That's how I'd do it, but you might have to do it a completely different way, because the way I'd find concentration is different ( I'd find mols before finding concentration in your problem).

LeRoy.
Mar 22nd, 2006, 04:22 PM
part (4)

molar mass = Y / N2 from part (3)

!<blocparty>!
Mar 22nd, 2006, 04:23 PM
I'm from Canada but I imagine the methods here are the same as the method in the US. The concentration will be the mols/V so you should just have to multiply the concentration by your volume to get mols alone. That's how I'd do it, but you might have to do it a completely different way, because the way I'd find concentration is different ( I'd find mols before finding concentration in your problem).

Yes... thats why its confusing me. The way it TELLS me to work out the molar concentration in question one is different. Its basically telling me that its mass/molecular mass... which is the formula I use for moles.

I just want to know is what I've worked out in question one just the concentration. If so, then I'll beed to work out the moles for question two.

LeRoy.
Mar 22nd, 2006, 04:25 PM
Right... so basically, what you worked out in question one, needs to be multiplied by the volume to get the moles?

So, the moles of KHP = moles NaOH. So concentration NaOH would be Moles KHP/volume?

I think that's what you said but our formula's are different.

Yes but if the acid was a dibasic acid then the formula would be different

It would be N1 *V1 = 2*N2*V2

1---> acid , 2---> base

For eg H2SO4 against NaOH

!<blocparty>!
Mar 22nd, 2006, 04:27 PM
Yes but if the acid was a dibasic acid then the formula would be different

It would be N1 *V1 = 2*N2*V2

1---> acid , 2---> base

Oh no we don't do anything like that. :p

LeRoy.
Mar 22nd, 2006, 04:28 PM
Oh no we don't do anything like that. :p

Then I'm sorry for omplicating things for you:wavey:

Yasmine
Mar 22nd, 2006, 04:28 PM
Ok here is my bit of help...
that's the first question;)

5.200 g (the mass I used) X1000 / 204.2(g/mol) X 250 (dm3)... right? (I'm not sure of the units, though.
--> you get a concentration meaning in mol/dm3 (or mol/l) I added the units just so you see...

Yasmine
Mar 22nd, 2006, 04:29 PM
Yes but if the acid was a dibasic acid then the formula would be different

It would be N1 *V1 = 2*N2*V2

1---> acid , 2---> base

For eg H2SO4 against NaOH
yes I would use that too...

!<blocparty>!
Mar 22nd, 2006, 04:30 PM
Then I'm sorry for omplicating things for you:wavey:

Sooo.... my second method on post 10 looks correct?! :bounce:

:scared:

LeRoy.
Mar 22nd, 2006, 04:34 PM
http://img.photobucket.com/albums/v697/bloc_party/chem2.jpg

Yes the lower half seems 100 % right to me :yeah:

!<blocparty>!
Mar 22nd, 2006, 04:36 PM
PHEW!

Thank you very much Yasmine, Just Me and someone else who's username I don't know... for helping. :D

It's only worth like 10 marks, but still! :D

ps. Would the units for question one be moldm-1? :o

LeRoy.
Mar 22nd, 2006, 04:37 PM
mol / dm^3 , yes

Yasmine
Mar 22nd, 2006, 04:37 PM
Question 2:
For 2, you need the molar concentration. Now, the formula we use to get concentration is moles/volume in dm cubed. BUT... I don't know what the moles are. Are the MOLES what I had for the first question? If so, I could do:

*moles in first question*/ volume (which was an average of 23.35cm3)/1000

= mol dm-3

I would use the fact that n=c*v and it tells you one mole of acid neutralises one mole of base
n(KHP)=n(NaOH) and you can write c(KHP)*v(KHP)=c(NaOH)*v(NaOH)
You've calculated the concentration of KHP above, you have the titration volumes and you can calculate the concentration of NaOH)

do the same for question 3 with the new titration volumes
and if you did the experiments twice do the average;)

hope it's clear :scared:

!<blocparty>!
Mar 22nd, 2006, 04:43 PM
Question 2:
For 2, you need the molar concentration. Now, the formula we use to get concentration is moles/volume in dm cubed. BUT... I don't know what the moles are. Are the MOLES what I had for the first question? If so, I could do:

*moles in first question*/ volume (which was an average of 23.35cm3)/1000

= mol dm-3

I would use the fact that n=c*v and it tells you one mole of acid neutralises one mole of base
n(KHP)=n(NaOH) and you can write c(KHP)*v(KHP)=c(NaOH)*v(NaOH)
You've calculated the concentration of KHP above, you have the titration volumes and you can calculate the concentration of NaOH)

do the same for question 3 with the new titration volumes
and if you did the experiments twice do the average;)

hope it's clear :scared:

Uhm. OK. :unsure: But why would

c(KHP)*v(KHP)=c(NaOH)*v(NaOH)

be the same? :confused: They are of different volumes?

Also, it tells me on the opening page to write an equasion for the reaction of HX and NaOH. What displaces what?

Yasmine
Mar 22nd, 2006, 04:45 PM
Yes the lower half seems 100 % right to me :yeah:
same for me;) it's about what I told you, you just presented it differently :yeah:

LeRoy.
Mar 22nd, 2006, 04:47 PM
NaOH + HX ---> NaX + H20

Its a reaction where an acid reacts with a base to from salt and water :p

LeRoy.
Mar 22nd, 2006, 04:48 PM
Uhm. OK. :unsure: But why would

c(KHP)*v(KHP)=c(NaOH)*v(NaOH)

be the same? :confused: They are of different volumes?

Also, it tells me on the opening page to write an equasion for the reaction of HX and NaOH. What displaces what?

because 1 mol KHP is equivalent to 1 mol NaOH so when you multiply conc (c) with volume(v) , you get moles(n) and you are basically equating moles of KHP to moles of NaOH in that equation Yasmine wrote.

Yasmine
Mar 22nd, 2006, 04:50 PM
Uhm. OK. :unsure: But why would

c(KHP)*v(KHP)=c(NaOH)*v(NaOH)

be the same? :confused: They are of different volumes?
yes but the concentrations are also different;) it tells you that one mole of KHP neutralises one mole of NaOH. so when the color changed, you wrote down the titration volumes? and that corresponds to the volumes of neutralisation. that's why I wrote that at that point n(KHP)=n(NaOH)

clearer?

Yasmine
Mar 22nd, 2006, 04:53 PM
NaOH + HX ---> NaX + H20
I agree with that :D

CooCooCachoo
Mar 22nd, 2006, 04:55 PM
Chemistry :yawn:

Yay for Social Sciences.

Grachka
Mar 22nd, 2006, 05:01 PM
Oh my.

I had no idea chemistry could be so breathtaking

!<blocparty>!
Mar 22nd, 2006, 05:03 PM
yes but the concentrations are also different;) it tells you that one mole of KHP neutralises one mole of NaOH. so when the color changed, you wrote down the titration volumes? and that corresponds to the volumes of neutralisation. that's why I wrote that at that point n(KHP)=n(NaOH)

clearer?

Yeah. I think I get it now. :o Me and maths = :smash: Give me written stuff to remember anyday. :p

!<blocparty>!
Mar 22nd, 2006, 05:04 PM
NaOH + HX ---> NaX + H20

Its a reaction where an acid reacts with a base to from salt and water :p

Thanks. Yes, we have learnt this too, but I would have never thought of applying it here.

I'm gonna be bad when the synoptic questions come around. :help:

Dexter
Mar 22nd, 2006, 05:06 PM
So happy that I finished my chemistry education 2 years ago :woohoo:

Yasmine
Mar 22nd, 2006, 05:12 PM
Yeah. I think I get it now. :o Me and maths = :smash: Give me written stuff to remember anyday. :p
With all this help you better get top mark for it :angel:

katiektc
Mar 22nd, 2006, 05:17 PM
Yeah. I think I get it now. :o Me and maths = :smash: Give me written stuff to remember anyday. :p

Me and maths never got on either! I hated it. Loved chemistry though, but why they make it a compulsory subject to have to get into med school is beyond me...I've never needed it or even thought about chemistry since the moment I finished my last exam ;)

Sorry I couldn't help you Tim! Biology is more my forte these days. Good luck with your exams! :)

!<blocparty>!
Mar 22nd, 2006, 05:41 PM
Me and maths never got on either! I hated it. Loved chemistry though, but why they make it a compulsory subject to have to get into med school is beyond me...I've never needed it or even thought about chemistry since the moment I finished my last exam ;)

Sorry I couldn't help you Tim! Biology is more my forte these days. Good luck with your exams! :)

We were discussing this today. Someone said that chemistry is officially the hardest A-level. Someone was arguing that maths is, though. ;)

I'm looooooooooving biology at the moment. We're doing all about the brain and its functions. I love that stuff. :yeah:

!<blocparty>!
Mar 22nd, 2006, 05:42 PM
With all this help you better get top mark for it :angel:

If I get it wrong, bad repping with ensure. :armed:

katiektc
Mar 22nd, 2006, 05:50 PM
We were discussing this today. Someone said that chemistry is officially the hardest A-level. Someone was arguing that maths is, though. ;)

I'm looooooooooving biology at the moment. We're doing all about the brain and its functions. I love that stuff. :yeah:

It's probably individual! I could do chemistry but could barely do maths at GCSE ;) while alot of people who 'got' maths couldn't do chemistry. Although the hardest A Level for me to do would be Art - I am shite ;)

BiologyRockz! :yeah: The brain, however, does not. It actually might start keeping me awake at night because it's anatomy & physiology is the hardest thing I have ever come across in my life - it scares me :scared:

;)

!<blocparty>!
Mar 22nd, 2006, 05:56 PM
It's probably individual! I could do chemistry but could barely do maths at GCSE ;) while alot of people who 'got' maths couldn't do chemistry. Although the hardest A Level for me to do would be Art - I am shite ;)

BiologyRockz! :yeah: The brain, however, does not. It actually might start keeping me awake at night because it's anatomy & physiology is the hardest thing I have ever come across in my life - it scares me :scared:

;)

Oh absolutely. GCSE maths was so hard! A level PE and Geography are much easier. :unsure:

I understand a lot of the in organic stuff in chem, I was doing really well during term and thought I could get a good grade for it. I got results back last week and it was an E. :help::sad:

And oh.... LOL! Well I guess I'll grow to hate the brain too. :p What about psychiatrics... have you done anything like that yet?

No Name Face
Mar 22nd, 2006, 06:01 PM
We were discussing this today. Someone said that chemistry is officially the hardest A-level. Someone was arguing that maths is, though. ;)

I'm looooooooooving biology at the moment. We're doing all about the brain and its functions. I love that stuff. :yeah:

chem was so much fun in high school. college chem though :scared:

i love biology.
psychology is like bio, but only about the brain. it really is a science, a fact i didn't know until i started taking upper level classes.

anyway, good luck tim. though you should go into business :yeah:

katiektc
Mar 22nd, 2006, 06:02 PM
Oh absolutely. GCSE maths was so hard! A level PE and Geography are much easier. :unsure:

I understand a lot of the in organic stuff in chem, I was doing really well during term and thought I could get a good grade for it. I got results back last week and it was an E. :help::sad:

And oh.... LOL! Well I guess I'll grow to hate the brain too. :p What about psychiatrics... have you done anything like that yet?

Ooh, we get to do a 6 week psychiatry rotation next year, as well as neurology, obs & gyn and specialities like that. It will be fab! Not like at the minute, I'm doing a 4 week project where I have to write a paper on - rheumatoid disease. Fun ;)

!<blocparty>!
Mar 22nd, 2006, 06:17 PM
chem was so much fun in high school. college chem though :scared:

i love biology.
psychology is like bio, but only about the brain. it really is a science, a fact i didn't know until i started taking upper level classes.

anyway, good luck tim. though you should go into business :yeah:

I wish I could take a year in american colleges to see the difference in standard.

Psychology would bore me, loads of people want to do it here. As Katie has found out, going into the brain too much is boring. Touching up on everything (like my current unit) is fun. (no pun intended)

Thank you. Yeah, business is my second choice. But I don't know if i'd make a good businessman.

!<blocparty>!
Mar 22nd, 2006, 06:19 PM
Ooh, we get to do a 6 week psychiatry rotation next year, as well as neurology, obs & gyn and specialities like that. It will be fab! Not like at the minute, I'm doing a 4 week project where I have to write a paper on - rheumatoid disease. Fun ;)

Oooh, that does sound fab. ;) You'll have to report to me how much you loved the psychiatry stuff. :yeah::p

Gyn? Oh my. :scared: Can you choose not to do that? :lol:

Rhematoid? :yawn: Don't you have exams in april?

RainyDays
Mar 23rd, 2006, 10:44 PM
Chemistry :yawn:

Yay for Social Sciences.

WORD.

katiektc
Mar 24th, 2006, 07:33 AM
Oooh, that does sound fab. ;) You'll have to report to me how much you loved the psychiatry stuff. :yeah::p

Gyn? Oh my. :scared: Can you choose not to do that? :lol:

Rhematoid? :yawn: Don't you have exams in april?

:lol: Ah, you have to go there with Gyn some time! *barf* ;)

Yep, I've 3 exams on 11th April but I have no time to study for them - oh well! They're only mocks anyway, my real exams aren't til July :yawn:

K-Dog
Mar 25th, 2006, 12:56 AM
I'm in AP Chem right now in my senior year. It is the hardest, most difficult class I have. Calc is a breeze compared to Chem. We are starting titrations right now, but myself and basically the rest of the class don't get it at all. Chemistry is probably the hardest class I'll even take because it is SO wide reaching with all the stuff you need to know for it.

K-Dog
Mar 25th, 2006, 01:03 AM
btw, is titration when you are trying to neutralize an acid or a base? i can prob do the math on this, but I don't know what a titration is. from what I've payed attention to, it is when you are neutralizing something with the opposite of it (ex. strong acid with a strong base). btw "Molar concentration" is also called molarity and is in mol/L.

K-Dog
Mar 25th, 2006, 01:05 AM
actually, this is pretty easy. I would just need to do the lab myself to fully understand it.

selking
Mar 25th, 2006, 02:02 AM
ewwww bad memories from last year

ampers&
Mar 25th, 2006, 02:08 AM
:tape:

OK, so I have this practical tomorrow but aren't 100% sure on a couple of things. I need to get a pretty high A, or else I'm fucked.

http://img.photobucket.com/albums/v697/bloc_party/chem.jpg

So anyway, the first one seems OK, you just do

5.200 (the mass I used) X1000 / 204.2 X 250... right? (I'm not sure of the units, though.

For 2, you need the molar concentration. Now, the formula we use to get concentration is moles/volume in dm cubed. BUT... I don't know what the moles are. Are the MOLES what I had for the first question? If so, I could do:

*moles in first question*/ volume (which was an average of 23.35cm3)/1000

= mol dm-3

and for question 3 it would just be the same as question 2 but with my second volume from titration 2 (which was 25.35cm3)

I think thats right... but I'm not sure if the concentration for the first question is the same as the moles. I have no other way of working out the moles for the C= N/V thing. :confused:

I hope you're following me. :p

So basically I just want to know how to work out the second question. Someone else suggested it could be... moles of KHP= molar concentravion X the titation volume (23.35) / 1000. Thus, that is the moles of NaOH, so, concentration NaOH would = moles/volume of NaOH (25cm3)/1000.

It's so stupid but I need to get it right.
Tim....it's simple really....the answer is orange....it's ALWAYS orange.

if you need any other help, feel free to ask me. :wavey: :D

K-Dog
Mar 25th, 2006, 02:10 AM
Tim....it's simple really....the answer is orange....it's ALWAYS orange.

if you need any other help, feel free to ask me. :wavey: :D

well sodium (Na) is orange is a flame test (i think). but I don't think that works with titration situations.

!<blocparty>!
Mar 25th, 2006, 02:12 AM
actually, this is pretty easy. I would just need to do the lab myself to fully understand it.

You don't know what a titration is, but, this is easy. :haha:;) And besides, the answers have already been posted. :)

Tim....it's simple really....the answer is orange....it's ALWAYS orange.

if you need any other help, feel free to ask me. :wavey: :D

Uhm, K. So, I put the molar mass of HX is orange. :unsure:

SJW
Mar 25th, 2006, 02:13 AM
I wish I could take a year in american colleges to see the difference in standard.

Psychology would bore me, loads of people want to do it here. As Katie has found out, going into the brain too much is boring. Touching up on everything (like my current unit) is fun. (no pun intended)

Thank you. Yeah, business is my second choice. But I don't know if i'd make a good businessman.

i'll tell you as soon as i get to my major electives.
damn core requirements.
American Political Science is like the hardest subject i've ever had to take by the way. US or UK. and i took some hard shit in the UK.
but English is easier in the US. i guess it depends on the subject and/or the person :shrug:

ampers&
Mar 25th, 2006, 02:13 AM
well sodium (Na) is orange is a flame test (i think). but I don't think that works with titration situations.

Uhm, K. So, I put the molar mass of HX is orange. :unsure:

absolutely! :D

!<blocparty>!
Mar 25th, 2006, 02:16 AM
i'll tell you as soon as i get to my major electives.
damn core requirements.
American Political Science is like the hardest subject i've ever had to take by the way. US or UK. and i took some hard shit in the UK.
but English is easier in the US. i guess it depends on the subject and/or the person :shrug:

Political Science? :unsure: You mean, politics, and science?

K-Dog
Mar 25th, 2006, 02:18 AM
You don't know what a titration is, but, this is easy. :haha:;) And besides, the answers have already been posted. :)

I need someone to explain it better. The math part is stuff we've already done. I think that is easy. I need to read up on my titration notes to fully understand what it is meant by it.

!<blocparty>!
Mar 25th, 2006, 02:18 AM
absolutely! :D

Monique | (*) says:
I'm majoring in english... the only thing I know about chemistry is that everything has different colors, that is all.

:unsure:

SJW
Mar 25th, 2006, 02:18 AM
Political Science? :unsure: You mean, politics, and science?

Political Science = the study of Politics.
it's sooooooooooooo hard but so interesting.
i think it's hard because i'm English. :sad:

G1Player2
Mar 25th, 2006, 02:21 AM
Political Science = the study of Politics.
it's sooooooooooooo hard but so interesting.
i think it's hard because i'm English. :sad:

I didn't think it was so bad but my friend who is an English major said it is the hardest class she ever took.

ampers&
Mar 25th, 2006, 02:21 AM
Political Science = the study of Politics.
it's sooooooooooooo hard but so interesting.
i think it's hard because i'm English. :sad:
but you're A'cing the class, right?

SJW
Mar 25th, 2006, 02:31 AM
I didn't think it was so bad but my friend who is an English major said it is the hardest class she ever took.

well when if you grow up in the US, no matter how little you know about current affairs, you still understand the basis of the way politics work.
i didn't. it's all new to me...and when i was in England i actually paid a little attention to US politics! most other people would have been even more baffled taking this class than i am

but you're A'cing the class, right?

i have this nasty habit of being able to ace my classes without any studying or effort.
this isnt one of those classes :(
i'm not failing but i have to work damn harder than i usually do :(