# Need help calculating the uncertainty for the acid dissociation constant for my IA report

## Recommended Posts

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

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 by norsul

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account. ×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.