Mel Posted June 16, 2009 Report Share Posted June 16, 2009 (edited) Okay, so I've been struggling in chemistry all year..I'm in HL right now but I'm switching into SL next year.My problem is that I have one final experiment that I have to do, and I am completely and utterly lost.Can anyone help me with my error calculations?(PS: I did a titration)example:pipette = +/- 0.06 mLgraduated cylinder = +/- 1.0 mLCa(OH)2 = +/- 0.001 gtitration (HCl mL difference) = +/- 0.4& PS: I'm having trouble figuring out the molarity of the Ca(OH)2I dissolved 0.1g of it in 100mL of water and titrated that with HCl, trying to figure out how stirring affected an equilibrium constant. Edited June 16, 2009 by Aboo Does the thread title really have to be in Caps? Reply Link to post Share on other sites More sharing options...
sweetnsimple786 Posted June 16, 2009 Report Share Posted June 16, 2009 (edited) Okay I'm probably no help whatsoever because I never learned how do figure out error. However, stirring wouldn't affect the equilibrium constant--only temperature does.Edit: Also, I'm not sure if you're asking, but to find [Ca(OH)2], you can convert grams to moles. Then multiply this by two because of the subscript. Once you have the number of moles, you can get molarity b/c your volume=.1L. Edited June 16, 2009 by sweetnsimple786 Reply Link to post Share on other sites More sharing options...
Sandwich Posted June 16, 2009 Report Share Posted June 16, 2009 (edited) For molarity of Ca(OH)2, mols = mass / mol massSo mols Ca(OH)2 = 0.1 / molar mass of Ca(OH)2.Mols = conc x volumeSo mols Ca(OH)2 = conc x 0.01 (0.01 being, unless I am mistaken, which I often am, 100mls in dm3)I don't have a periodic table to work it out.Do you have that big blue textbook by Geoffrey Neuss? He explains error calculations very well at the back of it Edited June 16, 2009 by Sandwich Reply Link to post Share on other sites More sharing options...
Mel Posted June 16, 2009 Author Report Share Posted June 16, 2009 However, stirring wouldn't affect the equilibrium constant--only temperature does.omg thank you for reminding me.. I knew that, I can't believe I forgot. Wow, that's really dumb of me.Thanks Reply Link to post Share on other sites More sharing options...
Steven Posted July 18, 2009 Report Share Posted July 18, 2009 i think to find error it is the smallest measurement marking on the measurement instrument you are using and divide that by half. for example if you are using a regular ruler then the smallest measurement marking is 1mm and thus the error is +/- 0.5mm Reply Link to post Share on other sites More sharing options...
Tilia Posted July 19, 2009 Report Share Posted July 19, 2009 You appear to know how to calculate, it's just the errors troubling you, right?When you add/subtract two values you add their absolute uncertainties.Eg, 2+-0.2 + 4 +-0.5 = 6 +_0.7When you multiply/divide you add the percentage errors, which are found byabsolute error/measurement x 100%So if the value is 4 +- 0.2, the percentage error is0.2/4 x 100% Reply Link to post Share on other sites More sharing options...
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