satisfied that you correctly calculated 95% ETOH to make 200mL of 80% ETOH (abov

Question

satisfied that you correctly calculated 95% ETOH to make 200mL of 80% ETOH (above), you walk to the lab and take a 250mL volumetrc flask and make the dilution based on your calculation above. You add the 95% ETOH and bring the solution to volume. As you are labeling the bottle as 80% ETOH, you realize your mistake, Oops! You did not measure a 200-mL volumetrc flask. So what is the actual concentration of the solution of the solution you just made? Show your work.

[I previously calculated 168.4 stock solution and 31,6 mL of RO water]

Explanation / Answer

Using the equation

                        Initial Concentration x Initial Volume = Final concentration x final volume

Thus initially, we took

95% x Volume to be taken = 80 % x 200 ml

Volume to be taken = 80 x 200/ 95

Volume to be taken = 168.4 ml of 95% ethanol to be taken

Second scenario

168.4 ml of 95% ethanol taken and volume made was 250 ml. Thus final volume becomes 250 ml, initial volume become 168.4 ml

So using the same above equation we get

Initial Concentration x Initial Volume = Final concentration x final volume

95 % x 168.4 ml = final conc. X 250ml

Final conc of solution becomes = 95% X 168.4/ 250

Final conc of solution becomes = 63.9%

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