Question s: Atomic absorption spectroscopy: Iron tablet Name: Liz Zharovsky Bench #: C19 Lab day and section: Tuesday - 2 1. How would each of the following problems in the procedure affect the measured value of the weight % of iron in the tablet (make it larger, smaller, no effect, or random effect). Explain why. i) The tablet is chipped off and its weight is smaller than the weight of other tablets. ii) The tablet is already wet when its weight is measured on a balance. iii) In Step 2 the boiling was performed for only 10 minutes and the tablet was not completely dissolved in HCl. iv) 30 mL of 6M HCl is used in Step 2 to dissolve the tablet instead of 25 mL of 6M HCl. v) In Step 7 the 5 mL pipet is rinsed only with distilled water and not with the solution from the 250 mL flask. vi) In Step 8 the meniscus of the added distilled water is below the 100 mL mark. Answer: i) If the weight is smaller than other tablets, that affects the measurement of weight % of iron by lessening the denominator of the fraction (weight of iron/weight of tablet). Thus, the weight % would be higher than it should be because the weight of iron stays the same divided by a smaller amount. ii) If the tablet is already wet when its weight is measured, it could have a greater mass than the tablet itself does.
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This note was uploaded on 01/23/2012 for the course CHEM 18a taught by Professor Dolnik during the Fall '06 term at Brandeis.