Hello,

For a Chemistry project i have to determine the starch concentration of two solutions of which i only know the extinction (which i had of course determined using a colorimeter) using a calibration line plotted in excel derived from samples  of which the concentration + extinction was known. The problem is that i forgot to note the molarity of the starch-solution - from which i derived my samples -, even though i did note the mass concentration in g/L. Therefore i made a graph in excel with the concentration is in g/L and the extinction. Is this a valid relation? Or do i need to know the molarity of the starch-solution?

Best regards,

Hans

Well since

[math]molarconcentration = \frac{{massconcentration}}{{molecularmass}}[/math]

and the molecular mass is a constant the form of your graph is OK,

but obviously for any result that needs to involve the the molar mass you will need that constant.

Thank you, very much!

Unless the starch molecule has a defined number of glucose monomers, I don't see how it can have a single molecular weight.  Polymers are not my strongest suit, but it might be possible to define an average molecular weight.

2 hours ago, BabcockHall said:

Unless the starch molecule has a defined number of glucose monomers, I don't see how it can have a single molecular weight.  Polymers are not my strongest suit, but it might be possible to define an average molecular weight.

I presume there is a particular starch involved.

This may be for a pharmacy course and pharmacists often use average molecular weights.

And 'starch' is a common constituent of pills various.