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Author Topic: mEq and mOsm and particles released  (Read 5381 times)

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nathanpaula

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mEq and mOsm and particles released
« on: January 09, 2006, 03:51:39 AM »

I have a couple of problems that i ahve been working on and I want to make sure that I am headed in the correct direction before I continue on.  My High School chemistry was long ago and far away...

Problem #1:  The first problem deals with magnesium sulfate MgSO4
     a.  One millimole of magnesium sulfate produces 4mEq = 2mOsm
     b.  The symbols for the two ions released are Mg(2+) and SO4(2-)
Is this correct?

Problem#2:  This problem deals with sodium sulfate.  Na2SO4
     a.  One millimole of sodium sulfate produces 4mEq = 3mOsm
THIS IS WHERE I AM NOT SURE...
     b.  The correct symbols for the particles released are Na(2+), S(2-) and O(2-)
     c.  The sulfate ion would have two charges.

Is my thinking and calculating correct?
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Borek

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Re:mEq and mOsm and particles released
« Reply #1 on: January 09, 2006, 04:19:23 AM »

Please clarify what you mean by Eq and Osm.

You are at least partially wrong, but I would prefer clarification before going into details.
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nathanpaula

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Re:mEq and mOsm and particles released
« Reply #2 on: January 09, 2006, 05:14:18 AM »

Hi,

     I guess I should have been clearer.  By mEq, what I am refering to is really milligrams/liter.  The human body has solutions which are dilute, so the measurements are given in mEq, which are milligrams per liter.  Example: One mEq of Na+ is 23, divided by one positive charge and is expressed as milligrams = 23 mg/L.  In another example, one mEq of Ca(+2)is 40 (atomic weight), divided by two (two positive charges) and is expressed in milligrams as 20mg/L.
     Using Na+, we know that one millimole(1/1000 of a mole) of sodium produces one mEq and one mOsm(milliosmole)

For question #1, I know that  1 millimole of magnesium sulfate produces 4 milliequivalants= 3 milliosmoles
   I believe a magnesium ion has two positive charges and a sulfate ion has two negative charges.
For question #2, I know that 1 millimole of sodium sulfate produces 4 milliequivalents = 3 milliosmoles
   I am not entirely sure about the charges and symbols on the individual particles

Thanks.  maybe this makes it a bit clearer.
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sdekivit

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Re:mEq and mOsm and particles released
« Reply #3 on: January 09, 2006, 05:15:26 AM »

Please clarify what you mean by Eq and Osm.

You are at least partially wrong, but I would prefer clarification before going into details.

no it's almost correct!

--> 1 mmol MgSO4 will yield 2 mmol ions, thus 2 mOsmol, and the charge is +2 for Mg thus 1 * 1 * 2 = 2 mEq  MgSO4

the amount of osmoles tells us something about the ions in solution, while equivalents are defined as amount of mols * charge * amount of ions produced

with Na2SO4 1 mmol yields 3mOsmol and 1 * 2 * 1 = 2 mEq
« Last Edit: January 09, 2006, 05:19:43 AM by sdekivit »
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nathanpaula

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Re:mEq and mOsm and particles released
« Reply #4 on: January 09, 2006, 05:57:40 AM »

no it's almost correct!

--> 1 mmol MgSO4 will yield 2 mmol ions, thus 2 mOsmol, and the charge is +2 for Mg thus 1 * 1 * 2 = 2 mEq  MgSO4

the amount of osmoles tells us something about the ions in solution, while equivalents are defined as amount of mols * charge * amount of ions produced

with Na2SO4 1 mmol yields 3mOsmol and 1 * 2 * 1 = 2 mEq

Thanks for the reply, but I want to understand how you got there.  I understand the 2 mOsm in MgSO4, but I do not quite understand how you get to 2 mEq.  When you say 1*1*2 =2, what does that represent?  I have dug through all sorts of resources and have not found a clear presentation of this.
Also, are my symbols correct for question#2?
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sdekivit

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Re:mEq and mOsm and particles released
« Reply #5 on: January 09, 2006, 06:20:00 AM »

Well, chemical equivalents are defined as amount of moles * charge of ion * number of ions

So if we have 1 mol NaCl and we take a look at Na-ions, than we get to 1 * (+1) * 1(ion) = 1 Eq
When looking at osmols, then you only look at the amount of ions that will be in solution, so 1 mol NaCl = 2 osmol NaCl

In Na2SO4, Na is (+1) and therefore 2 Na-ions are needed for 1 sulphate-ion: SO4(2-)
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nathanpaula

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Re:mEq and mOsm and particles released
« Reply #6 on: January 09, 2006, 07:10:51 AM »

Let's take a look at NaCl first, since it should be very basic and let's see if my reasoning is correct.

Looking at Na first, we have one mole of Na and multiply that by the charge of the ion which is (+1) and multiplied by number of ions which is 1.  Therefore we get 1*(+1)*1.  Is that correct?  We then take Cl and do the same thing.  We have one mole of Cl and multiply that by the charge which is (-1) and then multiply that by the number of ions which is 1.  We then get 1*(-1)*1 and equal 1.  This is where I am a bit fuzzy.  Does that mean that we have a mEq of 2 for NaCl?

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sdekivit

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Re:mEq and mOsm and particles released
« Reply #7 on: January 09, 2006, 09:40:23 AM »

no, we have 1 Eq of NaCl

--> we only look at the charge as a number, not if it's positive or negative.
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nathanpaula

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Re:mEq and mOsm and particles released
« Reply #8 on: January 09, 2006, 10:38:41 AM »

Thanks for the patience...Lets see if I have this right.  

NaCl  produces 2 mOsm and 1mEq
     1mEq is derived from multiplying 1*1*1=1  I don't use 2mOsm in the equation.

Na2SO4 yields 3mOsm and 2mEq because 1*2*1=2  

MgSO4 yields 2 mOsm and 2 mEq because 1*1*2=2

Question:  Why would I not use the equation 1*2*2 for NaSO4?  Do I not have 2 ions?  How do I compute this number?  Is it additive and I end up with 1 ion?  
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sdekivit

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Re:mEq and mOsm and particles released
« Reply #9 on: January 09, 2006, 10:44:56 AM »

if i have Na2SO4 (1 mmol) and we look at SO4(2-)-ions we get:

1 * 1(ion) * 2(charge) = 2 mEq, but because we have 2 Na and 1 SO4(2-) we get 3 mOsmol solution.

remember that Na = +1 and SO4 = 2-, so we need 2 Na for 1 SO4 to gain an electrical neutral salt.
« Last Edit: January 09, 2006, 10:47:33 AM by sdekivit »
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