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stroo
SILVER Member since Feb 2003

stroo

trusty sidekick to superman
Location: oxford, england, uk

Total posts: 799
Posted:Spent all hol avoiding doing chemistry coursework, and left it maaaajorly to the last minute...not tooo optimistic but no-one happens to know anything about activation energys (Ahhenius equation) in relation to the iodine clock reaction? any help would be muchly muchly appreciated and paid for with billions and trillions of hugs (and a few muffins perhaps too....)

Livin' on dreams and custard creams

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Gelfling
BRONZE Member since Jul 2004

Gelfling

Watcher of 80s cartoons
Location: Chepstow & Bristol, United Kin...

Total posts: 665
Posted:Nucleopoi may be of some help - I'll ask the Chemistry guys for you tomorrow and post more after. Good luck!



hug



and by the way could you do a favour for me please and have a go at these questions please?

EDITED_BY: Gelfling (1113755557)


>What do you think about the state of the Earth?
>I'm optimistic.
>So why do you look so sad?
>I'm not sure that my optimism is justified.

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Nucleopoi
BRONZE Member since Nov 2004

Nucleopoi

chemical attraction
Location: Ilkeston, Derbyshire, England

Total posts: 1097
Posted:what exactly do you want to know?
im doing my chem degree


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stroo
SILVER Member since Feb 2003

stroo

trusty sidekick to superman
Location: oxford, england, uk

Total posts: 799
Posted:ooh fantastic! well everything about actiavtion energy really...i really have no idea about it. Its for my plan on the kinetics of the iodine clock reaction...I'll PM you as i doubt many people will be interested... thank youuuu, the billions and trillions of hugs (and muffins) are on their way! x

Livin' on dreams and custard creams

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Birgit
BRONZE Member since Jan 2005

Birgit

had her carpal tunnel surgery already thanks v much
Location: Edinburgh, Scotland (UK)

Total posts: 4145
Posted:stroo, pm me, too... it's been a while since my chemistry stuff at uni, but maybe I can remember something useful smile

"vices are like genitals - most are ugly to behold, and yet we find that our own are dear to us."
(G.W. Dahlquist)

Owner of Dragosani's left half

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Gelfling
BRONZE Member since Jul 2004

Gelfling

Watcher of 80s cartoons
Location: Chepstow & Bristol, United Kin...

Total posts: 665
Posted:Hey - think these links will be useful - good luck
hug

Iodine Clock Movie
Think this will be useful


>What do you think about the state of the Earth?
>I'm optimistic.
>So why do you look so sad?
>I'm not sure that my optimism is justified.

Delete

stroo
SILVER Member since Feb 2003

stroo

trusty sidekick to superman
Location: oxford, england, uk

Total posts: 799
Posted:aww you guys are so sweet! thank you so much! just handed it in (everything apart from the final draft of the analysis anyway). Only just seen you're post birgit but thanks for the offer anyway hug, and heres one for you too gelfling hug

Livin' on dreams and custard creams

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Gelfling
BRONZE Member since Jul 2004

Gelfling

Watcher of 80s cartoons
Location: Chepstow & Bristol, United Kin...

Total posts: 665
Posted:Hope it helped.

Are you going to use Standard Error bars on your graphs - they always impress?


>What do you think about the state of the Earth?
>I'm optimistic.
>So why do you look so sad?
>I'm not sure that my optimism is justified.

Delete

Havokist
BRONZE Member since Dec 2004

Havokist


Location: Manchester, United Kingdom

Total posts: 2530
Posted:i know this is semi-hi-jacking stroo's thread hug but would anyone be able to explain the moles theory in a way that isn't baffleing? ubbangel

We are the music makers, We are the dreamers of dreams,
Wandering by lone sea-breakers, And sitting by desolate streams;
World-losers and world-forsakers, On whom the pale moon gleams;
We are the movers and shakers of the world for ever, it seems.

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Nucleopoi
BRONZE Member since Nov 2004

Nucleopoi

chemical attraction
Location: Ilkeston, Derbyshire, England

Total posts: 1097
Posted:what exactly dont you understand?

moles=mass/Mr
conc=moles/(volume/1000)
1 mole is equal to 6.023 x 10 ^23 atoms.


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Sniper
BRONZE Member since Jan 2005

Sniper

Snoochie-boochie-noochies!
Location: , United Kingdom

Total posts: 663
Posted:uh nukey take it back to gcse babe, he's 14... :P

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And all that's jazz
BRONZE Member since Jan 2005

member
Location: just behind your left shoulder...

Total posts: 92
Posted:A 'mole' is basically a measurement of the amount of something. You can have a mole of anything - a mole of H2O, a mole of petrol, a mole of volleyballs, anything.

In terms of chemicals (or anything else for that matter, but we'll stick to chemicals), the 'mole' is equal to a certain number of molecules - 6.022 x 10^23 molecules (Avogadro's Number).

That is, one mole of water contains 6.022 x 10^23 water molecules;
one mole of Iron (Fe) contains 6.022 x 10^23 molecules of iron etc.

This is the way to remember it - don't remember the number if you don't have to, but just remember that a mole is a set quantity of something that contains a certain number of that thing. It is, incidentally, quite a large number - can you imagine a mole of volleyballs - 6.022 x 10^23 volleyballs? That's alot of volleyballs.

Now, because a 'mole' is a set quantity, you can have different numbers of moles - you can have 2 moles (which will contain 2 sets of 6.022 x 10^23 molecules, = 1.2044 x 10^24 molecules) or 1/2 a mole, or 0.000001 moles, etc. It's just a set quantity, so you can have whatever proportion of it you want.


Now, to actually apply the concept to real life. As 6.022 x 10^23 is a ridiculously large and unwieldy number, it doesn't tend to get used much except in the formal definition of moles - you don't really want to spend your time counting out that many molecules of your chemical to do a reaction, you'd be there for a pretty fair chunk of eternity. So, how do we use moles in a practical sense?

The real beauty of moles is this - one mole of a substance is the amount of that substance whose weight in grams is equal to the atomic/molecular weight of that chemical.

For example, 1 mole of water is equal to 18.016g. The molecular weight of water is 16 + 2x1.008 (O + 2H) = 18.016

1 mole of sodium = 22.99g. The atomic weight of sodium is 22.99g


3.5 moles of methane (CH4) weighs 56.147g. the molecular weight of methane is 16.042 (C + 4H) and 3.5 x 16.042 = 56.147



So you see, for practical use and calculations, 1 mole of a chemical substance (be it ion, atom, molecule or whatever) is defined as the amount of that substance that weighs the same (in grams) as that substance's molecular weight.

The number of molecules that are required to get an amount of a chemical equal (in grams) to its atomic weight is always 6.022 x 10^23 molecules, no matter what the chemical substance is. So, both the theoretical (number of molecules) and practical (weight equal to molecular weight) definitions of a mole are true simultaneously - 6.022 x 10^23 molecules of a substance always weigh (in grams) the same as the molecular weight of the substance, and any amount of a substance equal in weight (in grams) to the molecular weight of the substance will contain 6.022 x 10^23 molecules of that substance.






Anyawy, I hope that helps, I may have gone way over, under or around your expectations. Good luck with it!


C8H18 + 12.5O2 ---------> 8CO2 + 9H2O + you know what

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And all that's jazz
BRONZE Member since Jan 2005

member
Location: just behind your left shoulder...

Total posts: 92
Posted:Oh, and one more thing - we jhave so far looked at moles only in terms of a quantity, but we can also talk about moles in terms of concentration.

You've probably so far described concentrations in terms of amount per litre or mL - for example, 10g/L or 14g/100mL etc.

For molar quantities, the principle is simlar - we are just talking about the number of moles of a substance per Litre of water, not the weight of a substance per litre.

For example, a 1M (1 molar) solution of a chemical is a solution that contains 1 mole of that chemical in 1L of water.

A 4M (4 molar) solution of sugar, for example, contains 4 moles of sugar dissolved in 1L of water.

A 0.0001M solution of NaCl (table salt) will contain 0,0001 moles of NaCl dissolved in 1L of water.

One thing to remember for molar quantities is that the number is always the number of moles dissolved in a litre of water, not any other quantity of water.

For example, if you have 100mL of a 1M solution of sugar, the concentration of that solution is the same as 1M of sugar in 1L of water; it does not mean 1M of sugar in the 100mL of water. The way to think of it is, if you have a quantity of a molar solution which is not 1L, the concentration of that solution is recorded as if there was 1L of the solution.

For example, say you have 100mL of a 1M NaCl solution. This does not contain 1M of NaCl - if you had 1L of the solution it would contain 1M of NaCl. As you only have 100mL of the solution, you have 100mL/1L = 0.1 times as much NaCl as if you had a litre. This means you have 0.1 x 1 moles = 0.1 moles in the 100mL

This may seem a bit confusing - the way to remember it is that molar concentrations always measure in number of moles per litre - different quantities of the same CONCENTRATION solution with contain different QUANTITIES of the substance being measured. However, if you had 1L of the different volume solutions, all would have the same number of moles in them.

For example, I have 100mL of a 1M solution of NaCl. I also have 300mL of this solution. The 100mL volume contains 0.1 moles of NaCl, and the 300mL volume contains 300mL/1L = 0.3 moles of NaCl. However, both solutions have the same concentration - if I had 1L of both solutions, both litres would contain the same amount of NaCl - 1mole.



The final thing to note is notation (giggle). If you see the notation mole or mol, this means quantity. If you see the notation molar of M, it means concentration and is equal to mol/L.






Have fun!

Jazz


C8H18 + 12.5O2 ---------> 8CO2 + 9H2O + you know what

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And all that's jazz
BRONZE Member since Jan 2005

member
Location: just behind your left shoulder...

Total posts: 92
Posted:My God, you poor person, I've set you a veritable tome to read. I never realised how much like my high school chem teacher I sounded. How depressing.

Jazz


C8H18 + 12.5O2 ---------> 8CO2 + 9H2O + you know what

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Sniper
BRONZE Member since Jan 2005

Sniper

Snoochie-boochie-noochies!
Location: , United Kingdom

Total posts: 663
Posted:dude he wanted help not a mental enema! you just wiped out his entire education!

ok maybe just mine... confused2


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Gelfling
BRONZE Member since Jul 2004

Gelfling

Watcher of 80s cartoons
Location: Chepstow & Bristol, United Kin...

Total posts: 665
Posted:Nah Sniper - that's a great set of notes on moles from Aartj - your high school chem teacher would be so proud wink

Hav - I'll e-mail you some help if you pm your e-mail address to me.


>What do you think about the state of the Earth?
>I'm optimistic.
>So why do you look so sad?
>I'm not sure that my optimism is justified.

Delete

KatP
SILVER Member since Jan 2005

KatP

Muddy fingernails
Location: Way oop norf, Scotland (UK)

Total posts: 505
Posted:Likewise Havokist. If you haven't got it yet pm me. I'm a Chemistry teacher so may be able to help. (When my brain stops hurting from Uberstaff!)

Sorry Stroo, didn't see your thread til today or would have helped you too. hug

I can also email you the helpsheets I've made up for my classes on various calculations. Sometimes it just takes a different method to get the hang of it. hug


Your mother was a hamster and your father smelt of elderberries!

KITTENS!!!!

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Havokist
BRONZE Member since Dec 2004

Havokist


Location: Manchester, United Kingdom

Total posts: 2530
Posted:thanks and all that's jazz, but you gave me a slightly more indepth explaination of the notes i have, and it's made me understand much clearer what i know already about the 6.022 x 10^23 and concentration of 1M in 100ml only bein 0.1M hug but the bit i still dont understand is when actually applying it to real life terms without major amounts

We are the music makers, We are the dreamers of dreams,
Wandering by lone sea-breakers, And sitting by desolate streams;
World-losers and world-forsakers, On whom the pale moon gleams;
We are the movers and shakers of the world for ever, it seems.

Delete


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