Sciencemadness Discussion Board

Calculation help

DubaiAmateurRocketry - 9-8-2013 at 14:01

Hey all.

How do i measure the lattice energy in the ionic bond in Lithium perchlorate, between Li+ and ClO4- ?

I found nothing about it so i tried to calculate my own using bornharber cycle, i know how it works, but how do i do the Electron affinity for perchlorate?

Atomization enthalpy of chlorine, etc ? can some one help me clear this the mess i dont understand ?

Thanks.

Dany - 9-8-2013 at 15:31

Quote: Originally posted by DubaiAmateurRocketry  
Hey all.

How do i measure the lattice energy in the ionic bond in Lithium perchlorate, between Li+ and ClO4- ?

I found nothing about it so i tried to calculate my own using bornharber cycle, i know how it works, but how do i do the Electron affinity for perchlorate?

Atomization enthalpy of chlorine, etc ? can some one help me clear this the mess i dont understand ?

Thanks.



Lithium Perchlorate has a low lattice energy of 723 kJ/mol.

see page 2 of this article, plus they mentioned a reference for this value.

hope this will help you.

Dany.

Attachment: Large Enhancement of the Ionic Conductivity in an Electron-Beam-Irradiated [Poly(ethylene glycol)]xLiClO4 Solid Polymer (417kB)
This file has been downloaded 416 times

to open the pdf download the file and add to the name the extension ".pdf "

[Edited on 10-8-2013 by Dany]

DubaiAmateurRocketry - 9-8-2013 at 23:08

Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Hey all.

How do i measure the lattice energy in the ionic bond in Lithium perchlorate, between Li+ and ClO4- ?

I found nothing about it so i tried to calculate my own using bornharber cycle, i know how it works, but how do i do the Electron affinity for perchlorate?

Atomization enthalpy of chlorine, etc ? can some one help me clear this the mess i dont understand ?

Thanks.



Lithium Perchlorate has a low lattice energy of 723 kJ/mol.

see page 2 of this article, plus they mentioned a reference for this value.

hope this will help you.

Dany.


Ok how do i add this calculation to my original exothermic decomposition ?

I calculated my self the decomposition of Lithium Perchlorate is -7jk/mol right ?

so, if the lattice energy is a 723, does it become -730 during the decompostion per mol ?

but then it does not make sense how exothermic it would be, but maybe is could. Can you help me a bit more here ?

Dany - 9-8-2013 at 23:32

Quote: Originally posted by DubaiAmateurRocketry  
Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Hey all.

How do i measure the lattice energy in the ionic bond in Lithium perchlorate, between Li+ and ClO4- ?

I found nothing about it so i tried to calculate my own using bornharber cycle, i know how it works, but how do i do the Electron affinity for perchlorate?

Atomization enthalpy of chlorine, etc ? can some one help me clear this the mess i dont understand ?

Thanks.



Lithium Perchlorate has a low lattice energy of 723 kJ/mol.

see page 2 of this article, plus they mentioned a reference for this value.

hope this will help you.

Dany.


Ok how do i add this calculation to my original exothermic decomposition ?

I calculated my self the decomposition of Lithium Perchlorate is -7jk/mol right ?

so, if the lattice energy is a 723, does it become -730 during the decompostion per mol ?

but then it does not make sense how exothermic it would be, but maybe is could. Can you help me a bit more here ?


Hello DubaiAmateurRocketry,

the lattice energy that you requested is the energy needed to separate one mole of LiCLO4 into free Lithium and perchlorate ion, lattice energy is always positive because you need to give the system energy to be able to break bonds. The heat of decomposition is different. to calculate this quantity you need the heat of formation of LiCLO4 (which is -380.74 kJ/mol, from NIST webbook). also you need to know the actual decomposition reaction (you need to know the species formed and the stoichiometry of the reaction). when heated LiCLO4 do not decompose into Li and CLO4 ion! when the decomposition reaction is known you can substract the heat of formation of products from the heat of reaction of LiCLO4 to get the global heat of reaction.

Dany.

[Edited on 10-8-2013 by Dany]

[Edited on 10-8-2013 by Dany]

DubaiAmateurRocketry - 10-8-2013 at 02:01

Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Hey all.

How do i measure the lattice energy in the ionic bond in Lithium perchlorate, between Li+ and ClO4- ?

I found nothing about it so i tried to calculate my own using bornharber cycle, i know how it works, but how do i do the Electron affinity for perchlorate?

Atomization enthalpy of chlorine, etc ? can some one help me clear this the mess i dont understand ?

Thanks.



Lithium Perchlorate has a low lattice energy of 723 kJ/mol.

see page 2 of this article, plus they mentioned a reference for this value.

hope this will help you.

Dany.


Ok how do i add this calculation to my original exothermic decomposition ?

I calculated my self the decomposition of Lithium Perchlorate is -7jk/mol right ?

so, if the lattice energy is a 723, does it become -730 during the decompostion per mol ?

but then it does not make sense how exothermic it would be, but maybe is could. Can you help me a bit more here ?


Hello DubaiAmateurRocketry,

the lattice energy that you requested is the energy needed to separate one mole of LiCLO4 into free Lithium and perchlorate ion, lattice energy is always positive because you need to give the system energy to be able to break bonds. The heat of decomposition is different. to calculate this quantity you need the heat of formation of LiCLO4 (which is -380.74 kJ/mol, from NIST webbook). also you need to know the actual decomposition reaction (you need to know the species formed and the stoichiometry of the reaction). when heated LiCLO4 do not decompose into Li and CLO4 ion! when the decomposition reaction is known you can substract the heat of formation of products from the heat of reaction of LiCLO4 to get the global heat of reaction.

Dany.

[Edited on 10-8-2013 by Dany]

[Edited on 10-8-2013 by Dany]


Oh yes i know that part,

The decomposition is LiClO4 + Heat = LiCl + 2O2

And it is -7 kJ/mol , when i calculated it my self.

What i wanted to calculate is --

When i dissolve lithium perchlorate in something, and heat it until it decompose assuming the liquid does not boil or anything, will it be more exothermic than normal ? which i expect so.

So, it is already -7 kj/mol, and when it decompose, it no longer need to break the Li+ ClO4- Before becoming LiCl and ClO4, I assume it to be much more exothermic than normal ? but not too exothermic but still ?

Dany - 10-8-2013 at 02:25

Quote: Originally posted by DubaiAmateurRocketry  
Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Hey all.

How do i measure the lattice energy in the ionic bond in Lithium perchlorate, between Li+ and ClO4- ?

I found nothing about it so i tried to calculate my own using bornharber cycle, i know how it works, but how do i do the Electron affinity for perchlorate?

Atomization enthalpy of chlorine, etc ? can some one help me clear this the mess i dont understand ?

Thanks.



Lithium Perchlorate has a low lattice energy of 723 kJ/mol.

see page 2 of this article, plus they mentioned a reference for this value.

hope this will help you.

Dany.


Ok how do i add this calculation to my original exothermic decomposition ?

I calculated my self the decomposition of Lithium Perchlorate is -7jk/mol right ?

so, if the lattice energy is a 723, does it become -730 during the decompostion per mol ?

but then it does not make sense how exothermic it would be, but maybe is could. Can you help me a bit more here ?


Hello DubaiAmateurRocketry,

the lattice energy that you requested is the energy needed to separate one mole of LiCLO4 into free Lithium and perchlorate ion, lattice energy is always positive because you need to give the system energy to be able to break bonds. The heat of decomposition is different. to calculate this quantity you need the heat of formation of LiCLO4 (which is -380.74 kJ/mol, from NIST webbook). also you need to know the actual decomposition reaction (you need to know the species formed and the stoichiometry of the reaction). when heated LiCLO4 do not decompose into Li and CLO4 ion! when the decomposition reaction is known you can substract the heat of formation of products from the heat of reaction of LiCLO4 to get the global heat of reaction.

Dany.

[Edited on 10-8-2013 by Dany]

[Edited on 10-8-2013 by Dany]


Oh yes i know that part,

The decomposition is LiClO4 + Heat = LiCl + 2O2

And it is -7 kJ/mol , when i calculated it my self.

What i wanted to calculate is --

When i dissolve lithium perchlorate in something, and heat it until it decompose assuming the liquid does not boil or anything, will it be more exothermic than normal ? which i expect so.

So, it is already -7 kj/mol, and when it decompose, it no longer need to break the Li+ ClO4- Before becoming LiCl and ClO4, I assume it to be much more exothermic than normal ? but not too exothermic but still ?


What are you talking about is not logical. who do you want to decompose LiCLO4 in solution without boiling off or decomposing the solvent? LiCLO4 need high temperature for decomposition. You cannot treat the decomposition of LiCLO4 without taking into account the solvent which i guess is your polymer. In this situation the problem is complicated because it is very likely that the polymer decompose before LiCLO4 and then, as the temperature increase the LiCLO4 react with the polymer and you have a complex decomposition products.

the lattice energy already given is the energy needed to obtain lithium cation and perchlorate anion in gaseous phase and it is different from dissolving the perchlorate in solution. you need to know the heat of solvatation which depend on the solvent.

Dany.

DubaiAmateurRocketry - 10-8-2013 at 05:37

Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Quote: Originally posted by Dany  
Quote: Originally posted by DubaiAmateurRocketry  
Hey all.

How do i measure the lattice energy in the ionic bond in Lithium perchlorate, between Li+ and ClO4- ?

I found nothing about it so i tried to calculate my own using bornharber cycle, i know how it works, but how do i do the Electron affinity for perchlorate?

Atomization enthalpy of chlorine, etc ? can some one help me clear this the mess i dont understand ?

Thanks.



Lithium Perchlorate has a low lattice energy of 723 kJ/mol.

see page 2 of this article, plus they mentioned a reference for this value.

hope this will help you.

Dany.


Ok how do i add this calculation to my original exothermic decomposition ?

I calculated my self the decomposition of Lithium Perchlorate is -7jk/mol right ?

so, if the lattice energy is a 723, does it become -730 during the decompostion per mol ?

but then it does not make sense how exothermic it would be, but maybe is could. Can you help me a bit more here ?


Hello DubaiAmateurRocketry,

the lattice energy that you requested is the energy needed to separate one mole of LiCLO4 into free Lithium and perchlorate ion, lattice energy is always positive because you need to give the system energy to be able to break bonds. The heat of decomposition is different. to calculate this quantity you need the heat of formation of LiCLO4 (which is -380.74 kJ/mol, from NIST webbook). also you need to know the actual decomposition reaction (you need to know the species formed and the stoichiometry of the reaction). when heated LiCLO4 do not decompose into Li and CLO4 ion! when the decomposition reaction is known you can substract the heat of formation of products from the heat of reaction of LiCLO4 to get the global heat of reaction.

Dany.

[Edited on 10-8-2013 by Dany]

[Edited on 10-8-2013 by Dany]


Oh yes i know that part,

The decomposition is LiClO4 + Heat = LiCl + 2O2

And it is -7 kJ/mol , when i calculated it my self.

What i wanted to calculate is --

When i dissolve lithium perchlorate in something, and heat it until it decompose assuming the liquid does not boil or anything, will it be more exothermic than normal ? which i expect so.

So, it is already -7 kj/mol, and when it decompose, it no longer need to break the Li+ ClO4- Before becoming LiCl and ClO4, I assume it to be much more exothermic than normal ? but not too exothermic but still ?


What are you talking about is not logical. who do you want to decompose LiCLO4 in solution without boiling off or decomposing the solvent? LiCLO4 need high temperature for decomposition. You cannot treat the decomposition of LiCLO4 without taking into account the solvent which i guess is your polymer. In this situation the problem is complicated because it is very likely that the polymer decompose before LiCLO4 and then, as the temperature increase the LiCLO4 react with the polymer and you have a complex decomposition products.

the lattice energy already given is the energy needed to obtain lithium cation and perchlorate anion in gaseous phase and it is different from dissolving the perchlorate in solution. you need to know the heat of solvatation which depend on the solvent.

Dany.


Yes i know that, but how would i calculate the decomposition of my propellant then ?

Lithium perchlorate REMAINS DISSOLVED when the prepolymer polymerizes. so Li+ and ClO4- is separated literally even when the propellant becomes a solid piece.

so, the decomposition is not -7 kj/mol any more.

it will be more exothermic, because the Li+ and ClO4- does not have to be separated any more, it is ALREADY separated before during mixing. Therefore the decomposition would be very exothermic.

And i want to calcualate it, if its possible.

bfesser - 10-8-2013 at 07:26

<img src="../scipics/_warn.png" /> <strong>DubaiAmateurRocketry</strong> and <strong>Dany</strong>, <em>stop using the <img src="./images/xpblue/quote.gif"> button!</em> <img src="../scipics/_warn.png" />

Use the <a href="post.php?action=reply&tid=25555"><img src="./images/xpblue/reply.gif" /></a> button when responding to the last post. We can all scroll, and know who you're replying to.

['Dissenters'; do you still not want me to remove unnecessary quotes?]

Dany - 10-8-2013 at 10:40

To avoid complication due to solvation i suggest you to perform calculation on LiCLO4 as if it is in the condensed form. On one hand this approximation is justified by the fact that the percentage of LiCLO4 in your polymer matrix is low compared to NH4ClO4 and on the other hand not all LiCLO4 present is in the ionic form when dissolved in the polymer. some will stay in crystalline state. So taking these two effect into account the error introduce to your calculation will be minimal. but just a question, are you sure that your polymer is capable to dissociate the LiCLO4 to form a Solid Polymer Electrolytes (SPE)? maybe you need to check out the electric conductivity of the matrix.

Dany.

watson.fawkes - 10-8-2013 at 11:34

Quote: Originally posted by bfesser  
['Dissenters'; do you still not want me to remove unnecessary quotes?]
Leave them alone. They are signalling that they don't care about the other users here particularly, which is useful information that you would remove by vandalizing their posts.

If you would like to do something actually useful, teach them in U2U that they can cut down quoted text, adding ellipses if necessary. The way you've been dealing with this issue so far, you're keeping the stupid stupid, the incompetent incompetent, and the discourteous discourteous by your vandalism instead of educating them.

But really, as you've said endless times, doesn't this meta-discussion belong in Forum Matters, rather than this thread, the one about the behavior in question? Or is it OK for moderators to do start such discussions, but not regular members? After all, I'm only replying to your raising the issue here.

DubaiAmateurRocketry - 10-8-2013 at 13:05

Quote: Originally posted by Dany  
To avoid complication due to solvation i suggest you to perform calculation on LiCLO4 as if it is in the condensed form. On one hand this approximation is justified by the fact that the percentage of LiCLO4 in your polymer matrix is low compared to NH4ClO4 and on the other hand not all LiCLO4 present is in the ionic form when dissolved in the polymer. some will stay in crystalline state. So taking these two effect into account the error introduce to your calculation will be minimal. but just a question, are you sure that your polymer is capable to dissociate the LiCLO4 to form a Solid Polymer Electrolytes (SPE)? maybe you need to check out the electric conductivity of the matrix.

Dany.


Umm nice idea, I will try that when i get back to my small lab.

Do you have any idea how would i calculate the thermal decomposition of Lithium perchlorate without considering the energy to break the ionic bond ?

can i calculate it just like the bond enthalpies ? 3 Cl-O, 1 Cl=O

broken, to form one LiCl ionic bond and 2 O=O ? Is that true ?

DubaiAmateurRocketry - 10-8-2013 at 14:15

Okay, now we know that Li+ and ClO4- have a 723 kJ/mol lattice energy bond, how do i calculate That, to my exothermic decomposition ?

The formation of enthalpy of LiClO4 = -380.99 kJ/mol

Formation of LiCl = -408.59 kJ/mol

I am trying to find how exothermic the decomposition of Lithium perchlorate would be , assuming that the lattice energy is ignored, so if i cancel 723 kJ/mol during the decompostion, and the decomposition is already -7 kj/mol, how do i calculate then ? does it become -730 kJ/mol ? but it would be TOO exothermic and dosnt make sense ? since the formation of LiCl is only -408.59, how can this get over -730 ? I dont think i can just add or subtract the lattice energy ? can i ?


I am so eager to know the answer can someone help me please ? Cant fall asleep without knowing it !

Many thanks.

[Edited on 10-8-2013 by DubaiAmateurRocketry]

Dany - 10-8-2013 at 20:55

Here's the calculation, with example of decomposition of KClO4 and a reference value. first, all heat of formation are taken from NIST webbook:

KClO4: -430.12 kJ/mol
KCl: -436.68 kJ/mol

LiClO4: -380.74 kJ/mol
LiCl: -408.27 Kj/mol

the assumed decomposition reaction is:

MClO4=MCl+2O2 (where M= K or Li)

in the case of KCLO4, heat of formation of product (KCl)-heat of formation of KClO4= -436.68+430.12= -6.56 kJ/mol, the value reported in the attached article is -4.02 kJ/mol (close value).

doing the same calculation for LiCLO4 you'll find -27.26 kJ/mol (and not -7 kJ/mol).

and for the last time: the lattice energy is the heat required to separate the 2 ion in gas phase. DECOMPOSITION IS ANOTHER STORY!
And yes, compared to KClO4, LiClO4 decomposition is approximately 4 time more exothermic.

Dany.


Attachment: Heat of Decomposition of Potassium Perchlorate.pdf (1.1MB)
This file has been downloaded 455 times

[Edited on 11-8-2013 by Dany]

DubaiAmateurRocketry - 27-8-2013 at 10:41

hey i just tested if my propellant conduct electricity, and it does !!!!