norsul Posted May 31, 2012 Report Share Posted May 31, 2012 (edited) Hi guys, I'm sorry that the title is a little vague, but I really couldn't come up with anything more clever. So, this is the case: For my lab report I needed to calculate the the acid dissociation constant of an unknown weak monoprotic acid. The values which I could measure were mass (the acid was pure), volume and ph (plus the molar mass of the acid given by the teacher). So to simplify the process, I derived a fancy formula that allows me to do it in one step, instead of going through like five of them (don't worry, I've checked the correctness a million times, so there are no errors in this part). But then I had to calculate the uncertainty for my acid dissociation constant, I got stuck. I have no problems with the uncertainty calculation rules, but my formula has like fractions within fractions and stuff in exponents. I first though that I could avoid the complexity if I just didn't use the formula, but went step by step, and I was wrong, it seemed just as complicated. So I came here to seek help from you people . And the question is: How on earth do I calculate the damn uncertainty for the acid dissociation constant? dx - uncertainty of x m - mass of the acid V - total volume of the solution ph - ph-value of the solution M - Molar mass of the acid (doesn't have an uncertainty because it's provided by the teacher) Here are the values: dm -> +/- 0.001 g, dV -> +/- 0.001 dm^3, d(pH) -> +/- 0.05, M = 46.026 gmol^-1 The formula is in the attachment or here is a download link: http://www.mediafire...3jnei8c16e7khx6. By the way, from reading my explanation, you may see some fundamental errors in how I collected or processed data, this is because I only explained the things relevant to the question, and I would appreciate if your answers would also be focused on the question, and not on the other parts. Edited May 31, 2012 by norsul Reply Link to post Share on other sites More sharing options...
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