For the analysis of a sample , 3 beakers containing 25 mL of the sample ,...
For the analysis of a sample , 3 beakers containing 25 mL of the sample , each added with 5 mL phosphoric acid and then treated differently (some added with KIO4 while one was added with 5 mL of 2 mM Mn standard) before being transferred into a 50-mL volumetric flask and then added with water to the 50 mL mark. The absorbance reading after zeroing with the blank is 0.850 for the sample with added standard and 0.500 for just the sample. Determine the concentration of the Mn in the original sample
Homework Answers
Absorbance is directly proportional to concentration.
Let's say x mM of original sample in dilute.
5 mL of 2 mM standard diluted to 50 mL.concentration of standard in beaker= 5×2/50=0.2 mM
A1/A2 = x/x+0.2=0.5/0.85
0.85x=0.5x + 0.1
0.35x=0.1
x=0.286 mM.
25 mL of sample diluted to 50 mL or 50/25=2 times diluted.
Original Mn sample concentration=0.286×2= 0.572 mM.
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