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### Topic: Sodium Ascorbate in mOsm/L?  (Read 1038 times)

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#### Simmons

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##### Sodium Ascorbate in mOsm/L?
« on: May 11, 2019, 04:36:08 AM »
If 200 grams of Sodium ascorbate is dissolved in 1000 mL of normal saline, what would the net osmolarity in mOsm/L of the solute and what formula is used to calculate it?

Thanks.

#### Borek

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #1 on: May 11, 2019, 05:48:39 AM »
Per forum rules you have to show your attempts at solving the problem before receiving help.

Hint: what formulas related to osmolarity do you know?
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#### Simmons

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #2 on: May 11, 2019, 05:22:36 PM »
Apologize for that..

I have scarce info regrading molarity..

solute weight/ molar mass= moles of solute.

In this case 50 grams of sodium ascorabte / 198.11 (gm/L) = 0.25 moles.

Osmolarity=  (total mOsm/ total mL) X (1000/L)= mOsm/L.

That's it....what do I put in since have sodium ascorbate 99% and in 0.9% saline???

Thanks.

#### Borek

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #3 on: May 11, 2019, 07:47:04 PM »
Hint: total osmolality is a sum of all individual osmolalities.

(That's only an approximation, that works best for diluted solutions, but I doubt you are expected to use more advanced approach).
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#### Simmons

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #4 on: May 12, 2019, 03:40:44 AM »
total osmolality is a sum of all individual osmolalities. ..Thanks.

But I want the individual osmolarity of sodium ascorabte 200 grams 99% in .9% of saline??

Any more hints??

#### Simmons

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #5 on: May 12, 2019, 03:47:23 AM »
I ain't getting any email notifications??

#### AWK

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #6 on: May 12, 2019, 05:18:08 AM »
Adding 200 g of sodium ascorbate to 1 L of saline you change volume, I guess, more than 100 ml. In the calculation of the osmotic concentration without taking into account the density of solution, this gives you an error of about 20 %.
Such calculations make no sense. In student calculation, usually, 5 % error is a limit.
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#### Simmons

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #7 on: May 12, 2019, 05:36:34 AM »
Adding 200 g of sodium ascorbate to 1 L of saline you change volume, I guess, more than 100 ml. In the calculation of the osmotic concentration without taking into account the density of solution, this gives you an error of about 20 %.
Such calculations make no sense. In student calculation, usually, 5 % error is a limit.

Volume changed, correct....so I destroyed approx 200ml of saline prior to mixing sod acorabte.

What formula did you use to calculate the osmolarity that gave an error of 20%?

I want to know the formula to calculate osmolarity of 200 grams sod. acorbate in the final solution.

#### AWK

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #8 on: May 12, 2019, 05:49:36 AM »
It does not matter how you prepared your solution. I do not believe that you got a clear solution with 200 ml of saline. The final volume will be over 1100 ml. You can find a density table for sodium ascorbate (food additive E301) but rather not for mixed solution E301 + NaCl. Use the density of 16.67 % sodium ascorbate and calculate molarity for 9 g of NaCl and 200 g of E301 in the new volume. Then the calculation of osmotic concentration is straightforward. This time the error will be ~2 % (estimation).
« Last Edit: May 12, 2019, 06:06:15 AM by AWK »
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#### Simmons

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #9 on: May 12, 2019, 06:05:26 AM »
Density x total molarity (of 9 grams of NaCl + 200 grams SA) / total volume= Osmotic concentration of the sodium ascorbate?

Thanks.

#### AWK

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #10 on: May 12, 2019, 06:07:59 AM »
No. Osmotic concentration is a simple function of molar concentration. Never they are equal for salts.
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#### Simmons

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #11 on: May 12, 2019, 06:10:29 AM »
Then the calculation of osmotic concentration is straightforward. This time the error will be ~2 % (estimation).

How did you come up with this?

thanks.

#### Simmons

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #12 on: May 12, 2019, 06:13:13 AM »
Is it possible to calculate the osmolarity in mosm/L of sodium ascorbate in 0.9% saline ( any amount 50 grams-200 grams/ volume 500-1000 ml)..simple...yes or no?

thanks.

#### AWK

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #13 on: May 12, 2019, 06:19:51 AM »
Then the calculation of osmotic concentration is straightforward. This time the error will be ~2 % (estimation).

How did you come up with this?

thanks.

Estimation of the error before doing the calculations is a real skill for scientific and engineering calculations. I did this based on an estimate of the density of the solution within 0.02 error for a density of about 1.1
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#### AWK

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##### Re: Sodium Ascorbate in mOsm/L?
« Reply #14 on: May 12, 2019, 06:20:38 AM »
Is it possible to calculate the osmolarity in mosm/L of sodium ascorbate in 0.9% saline ( any amount 50 grams-200 grams/ volume 500-1000 ml)..simple...yes or no?

thanks.
Within 20 % error - yes.
Within 5 % error - no.
AWK