Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Simmons on May 11, 2019, 04:36:08 AM
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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.
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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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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.
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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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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??
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I ain't getting any email notifications??
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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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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.
Thanks for the reply.
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.
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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).
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Density x total molarity (of 9 grams of NaCl + 200 grams SA) / total volume= Osmotic concentration of the sodium ascorbate?
Thanks.
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No. Osmotic concentration is a simple function of molar concentration. Never they are equal for salts.
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Then the calculation of osmotic concentration is straightforward. This time the error will be ~2 % (estimation).
How did you come up with this?
thanks.
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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.
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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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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.
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Within 20 % error - yes.
Within 5 % error - no.
Thanks.
I'm not concerned about the error 5 or 20% but the osmolarity of sodium ascorbate in grams in the final solution.
Care to share the formula how I could measure that, and how you come up with 5-20% errors?
Thanks again.
PS: An acquaintance has tried with 100 grams in 1000 ml, with normal osmolarity of 300 mosm/l....but is away, otherwise won't have bothered you.
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I told you - just find densities of sodium ascorbate solutions. Taking them as an approximation you can calculate osmotic concentrations with an error of about 2 % for 200 g sodium ascorbate and about 5% for 50 g of sodium ascorbate.
To lowering error you can measure densities of a few solutions with salt and then interpolate densities - this may give you the error even lower than 1 % (but this depends on the precision of measurements) but still neglecting osmotic coefficient which changes with concentration.
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I'm getting 1 Osmol/L, of sod. ascorbate 100 grams dissolved in 1 liter of water.
1. How much would that be in mOsmol/L?
2. How much would be Osmol/L, IF it were 0.9 % saline 1 liter?
Thanks.
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I'm getting 1 Osmol/L, of sod. ascorbate 100 grams dissolved in 1 liter of water.
1. How much would that be in mOsmol/L?
2. How much would be Osmol/L, IF it were 0.9 % saline 1 liter?
Thanks.
1 Osmol/L - this value is accepted with an error slightly less than 5 %
Converting Osmol/L to mOsmol/L is very simple.
Osmotic concentration is additive