HW 8-calibration curves

HW 8-calibration curves - gave an absorbance of 0.262 in an...

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Due Friday Oct 21 1. Use the following mass spectrometry data and blank to construct a calibration curve with trend line: CH 4 (vol%): 0 0.062 0.122 0.245 0.486 0.971 1.921 Signal (mV): 9.1 47.5 95.6 193.8 387.5 812.5 1671.9 2. Replicate measurements of an unknown gave 152.1, 154.9, 153.9, and 155.1 mV, and a blank gave 8.2, 9.4, 10.6, and 7.8 mV. (a) Find the concentration of the unknown. (b) Why might the replicate series of blanks be taken right before the unknown rather than for the calibration curve? What might be good or bad about doing that? 3. An unknown sample of Cu 2+
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Unformatted text preview: gave an absorbance of 0.262 in an atomic absorption analysis. Then 1.00 mL of a solution containing 100.0 g/mL Cu +2 was mixed with 95.0 mL of unknown, and the mixture was diluted to 100.0 mL in a volumetric flask. The absorbance of the new solution was 0.500. a) Denoting the initial, unknown concentration as [Cu 2+ ] i , write an expression for the final concentration, [Cu +2 ] f , after dilution. Units of concentration are ug/mL. b) In a similar manner, write the final concentration of added standard Cu 2+ , designated as [S] f . c) Find [Cu 2+ ] i in the unknown....
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