Titration of the acid measure out 1000 ml of the

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Unformatted text preview: concentration (four significant digits) of the base and proceed to titration of the acid. For the standardization of the base, we will be using potassium hydrogen phthalate (KHP) as our primary standard (molecular mass 204.22 g/mol). Use a CLEAN DRY spatula to measure out about 0.4 grams of KHP (you do not need exactly 0.4 g, but you do need to know exactly how much you do have to as many significant figures as possible). If your lab instructor requests you to do so, add a couple of drops of phenolphthaliene. Titrate the sample either to the endpoint, or using the Pasco system to collect data as your lab instructor requests. Perform at least three titrations; if any of the runs are off by more than 0.04 mL from any other run, perform a fourth titration and discard the titration that seems to most significantly disagree with the other runs. Determine the exact concentration of the base from this step. Dilution of the Acid: The vinegar is too concentrated as it is to perform a titration, so make a dilution by putting 5.00 mL of vinegar (using a pipette) into a 50.00 mL volumetric flask and diluting as usual. This dilution means the solution you will be titrating is 10 times Dakota State University page 162 of 232 Experiment 15: Titration of Vinegar General Chemistry I and II Lab Manual weaker than the original vinegar. To take this dilution factor into account, multiply the concentration of the diluted sample by 10 to get the concentration of the original vinegar. Titration of the Acid: Measure out 10.00 mL of the diluted solution using a pipette. If your lab instructor requests you to do so, add a couple of drops of phenolphthaliene. Titrate the sample either to the endpoint, or using the Pasco system to collect data as your lab instructor requests. Perform at least three titrations; if any of the runs are off by more than 0.04 mL from any other run, perform a fourth titration and discard the titration that seems to most significantly disagree with the other runs. Determine the concentration of the acid from this step. Calculations: Standardization: KHP is a monoprotic acid, so the reaction can be simplified as KHP (aq) + NaOH (aq) à KNaP (aq) + H2 O (l) Using standard stoichiometric techniques, calculate the molarity of NaOH for each run. Take the average and determine the standard deviation. Concentration of the Acetic Acid: The acid is monoprotic, so again, we can write HA (aq) + NaOH (aq) à NaA (aq) + H2 O (l) Use standard stoichiometric techniques to calculate the moles of acid for each run. Don’t forget to take the dilution into account; once you calculate the concentration of acetic acid in the diluted solution, multiply by four to get the concentration of the original vinegar. Convert the concentration from molarity to % w/v in the standard method. Take the average and determine the standard deviation. Dakota State University page 163 of 232 Experiment 15: Titration of Vinegar General Chemistry I and II Lab Manual Observations: Standardization: Run Mass KHP Initial buret Final buret volume base molarity 1 2 3 4 (if necessary) Average molarity: Standard Deviation: Observations: Dakota State University page 1...
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