CPR – Primary Standard Solutions Preparing any solution with manufactured volumetric glassware and precision analytical balances will always yield an uncertainty in the precision of the solution’s final concentration. In this assignment, the concentration of 0.018M NaCN must satisfy a precision of 0.5% using at least a 50mL volumetric flask. To start off my procedure, I decided to test a 50mL volumetric flask because in a real lab, scientists should always minimize the amount of waste. I found 0.0009 mol of NaCN in a 50mL flask by multiplying 0.018M by 0.05L. To find grams, I multiplied 0.0009 mol by NaCN’s molecular weight (49.01g/mol) and got 0.0441g (sample weight). I rounded grams to four decimal places because it has to match the sensitivity of the balance, which has four decimal places. Finding grams is necessary because it is required for calculating relative error, which determines the precision of a solution. I calculated relative error by adding 0.0003g/0.0441g (sensitivity of balance divided by grams of NaCN) to 0.04mL/50.00mL (tolerance of 50mL flask
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This note was uploaded on 04/03/2008 for the course CHEM 14BL taught by Professor Pang during the Winter '07 term at UCLA.