Can anybody help me to prepare 3x 10 -4 concentrated solution of carboxymethyl cellulose polymer( avg Mw 250,000)
As you know, CMC has -CH2COOH groups instead of the -OH groups & the carboxymethyl will usually have sodium replacing the acidic hydrogen. The whole substitution is about 0.4 up to 1.5 percent . If we take the upper limit, then the molar mass of the CRU "constitutional repeating unit"= 282.18 g/mol. This is what is needed in the calculation of (assuming the molar concentration or molarity): M =n/V & n = wt./molar mass . Hence 3 X 10 -4 = (wt/282.18)/1liter solution.
Therefore, the weight of CMC required = 0.08465 g. for each one liter solution. Of course, you know that we bring 1st the CMC & add the solvent until there is total solution of one liter.
In this caculation(and in others), the large average M.Wt. of the polymer is NOT used. Calculation of yields, conc'ns...etc. are based on the molar mass of the CRU.
Dear Dr. Nizar Matar,
Thanks for your reply, at the same time I have one doubt, The molar mass of Sodium carboxy methyl cellouse and carboxy methyl cellulose molar mass of the CRU is same or different?. I had purchased Na CMC from sigma aldrich http://www.sigmaaldrich.com/catalog/product/aldrich/419311?lang=en®ion=IN . I would like to prepare 3x 10 -4 of this Na CMC only. Could you please clarifi my doubt?
Dear Sir,
First of all sorry for many questions at a time, but I would like to know the polyacrylic acid http://www.sigmaaldrich.com/catalog/product/aldrich/523925?lang=en®ion=IN molar mass of the CRU and sodium alginate http://www.sigmaaldrich.com/catalog/product/aldrich/w201502?lang=en®ion=IN molar mass of the CRU.
Thanks in advance
Prathap
The molar mass of the CRU of poly (acrylic acid) = 72.02 g/mol exactly.
The molar mass of the CRU of sodium alginate "the sodium salt of alginic acid" (C6H7NaO6)n :
198.11 (theoretical); 222 (actual average). I think, the average is better adopted.
Note: the typical average molecular mass of sodium alginate is 10,000 - 600,000 .
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