The % error in the extrapolated results is highly dependent on the error associa
ID: 502255 • Letter: T
Question
The % error in the extrapolated results is highly dependent on the error associated with the volume of lead (II) nitrate solution used in each titration and the volume of potassium iodide solutions need to initiate precipitation in each trial. Given the data below, calculate maximum % error associated with each of the typical measurements below. a. 100.00 mL of lead(II) nitrate solution measured using a 50.00 mL pipette with a tolerance of plusminus 0.05 mL. b. 100.00 mL of lead(II) nitrate solution measured using a 100.00 mL of volumetric flask with a tolerance of plusminus 0.02 mL. c. 7.42 mL of potassium iodide solution titrated from a 50.00 mL buret with a tolerance of plusminus 0.02 mL. Based on the calculations in question 1, which measurement introduces the greatest error? Can you suggest at least one possible modification to the procedure to improve the precision associated with individual titration points? Discuss how each of the following conditions might affect the volume of 0.200 M potassium iodide needed to reach the precipitation end point in a typical titration. a. The lead(II) nitrate solution was prepared in 0.05 M NaCl instead of deionized water. b. The temperature in the lab increased by 3 degree C.Explanation / Answer
1.
(a). 50 ml pipette having tolerance of 0.05 ml, so max. error would be 0.05x2 = 0.1 ml
so for 100 ml of solution it will be 0.1x2 = 0.2 ml
(b) 100 ml volumetric flask having a tolerance of 0.02 ml, so max. error will be 0.02x2 = 0.04 ml
(c) 50 ml buret have tolerance of 0.02 ml, so max. error 0.02x2 = 0.04 ml
For 7.42 ml pf solution max. error = (0.04x7.42)/50 = 0.006 ml
2. based on the calculation it is measurement a. which incorporates greatest error.
one possible suggestion is to use 100 ml pipette for measuring 100 ml of lead solution rather than using 50 ml of pipette.
3. If KI is prepared in NaCl solution, then during titration PbCl2 will also precipitate from the solution incorporating error in the measurement.
Temperature has effect on the solubility product of ionic compound. So if temperature increases then solubility of lead nitrate will increase to some extent as a result more KI will be required to induce precipitation.
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