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tousif2663
tousif2663
14.11.2019 • 
Chemistry

Several of the methods for water analysis that you completed with your group required the construction and use of a beer-lambert plot like the one given below for quantifying chromium (vi) ions in groundwater (cr6+). in the preparation of the unknown sample for chromium (vi) analysis, 70 ml of a groundwater sample was placed in a 100 ml volumetric flask with 1 ml of 3 m sulfuric acid and 2 ml of diphenyl carbazide (this reacts with the cr6+ ions at ph 2 to form a red-violet compound). the solution was diluted to the mark, the flask was shaken thoroughly, and the absorbance was measured at 540 nm. three unknown samples that were prepared in this way had absorbances of 0.14, 0.066 and 0.084. the following beer-lambert plot was constructed using standard chromium (vi) solutions. the equation of the line is given as y= 0.223x+0.0008. the r2 value is 0.9991. give the average concentration of the water sample after accounting for the dilution that occurred during the sample preparation described above. give your answer in units of mg cr/l

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