You determine the acetic acid (HOAc) content of vinegar by titrating with a sodium hydroxide standard solution to a phenolphthalein (an indicator) end point. An approximately 5-mL sample of vinegar is weighed on an analytical balance in a weighing boat and this is found to be 5.0268 g. The standard deviation in making a single weighing is 0.2 mg. The sodium hydroxide must be accurately standardised (this means its concentration must be accurately determined) by titrating known mass of high-purity potassium hydrogen phthalate, and three such titrations give molar concentrations of
You determine the acetic acid (HOAc) content of vinegar by titrating with a sodium hydroxide standard solution to a phenolphthalein (an indicator) end point. An approximately 5-mL sample of vinegar is weighed on an analytical balance in a weighing boat and this is found to be 5.0268 g. The standard deviation in making a single weighing is 0.2 mg. The sodium hydroxide must be accurately standardised (this means its concentration must be accurately determined) by titrating known mass of high-purity potassium hydrogen phthalate, and three such titrations give molar concentrations of 0.1167, 0.1163 and 0.1164 mol L-1. A volume of 36.78 mL of sodium hydroxide is used to titrate each sample. The standard deviation of the burette used is 0.02 mL. Calculate the percentage of acetic acid in the vinegar and its standard deviation.
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