In experiment V, “ISE: The Determination of Chloride”, the concentration of an Unknown Chloride solution, and the Wt% of NaCl in a sample of celery salt, were both determined. To determine the concentration of an Unknown Chloride solution, a Calibration plot is first prepared. The Calibration plot is made by first measuring a series of known concentrations of Cl- (with the same activity of the unknown solution) and obtaining a set of E-values for these standards -A graph is then plotted from the corresponding E-values vs. the logarithm of the concentration of Cl-. Once all the data points have been plotted, the slope of the line is determined (found by using a least squares calculation) -which is then used (the slope) to find the concentration of the unknown from the measured E-value of the unknown chloride solution. In the determination of the Wt% of NaCl in a sample of celery salt, the method of standard additions was used to find the Wt% of NaCl in our celery sample.
B.Standard Additions Method
A.Concentration of Chloride in the Calibration Solution
B.Calculation of Slope, Intercept and Equation of for the Calibration Line i.LLS Table
C.Theoreical Electrode Slope & Relative Error of Measured Electrode
D.Concentration of the Cl- Unknown
E.Wt% Cl- in Unknown
F.Y-Axis Variable for the Standard Additions Plot, Value of Vs’
G. Concentration of Chloride in Celery Sample (ppm & M )
H.Calculation of the Wt% NaCl in Solid Celery Salt
IV.Data and Results
See Attached Graph Calibration Plot.
Data Points for Calibration Plot.
Log [Cl-]E (mV)
B.Standard Additions Data
i.Standard Additions Graph
See Attached Graph Standard Additions Plot
ii.Standard Additions Data Table
Data points for the Standard Additions Plots
Vol (mL) KCl AddedPotential (mV)Y-Values
1.17(4) mL62 mV22.07(7) mL
5.01(2) mL56 mV28.36(2) mL
10.00(8) mL50 mV36.58(9) mL
Concentration of KCl: 0.1005M
Volume of KCl Solution Used: 250 mL
Unknown Weight: 0.1049g
Volume of Unknown Solution Used: 250mL
Concentration of Unknown: 0.00147 M
Wt% Cl- of Unknown: 12.25%
Concentration of Cl- in Celery Sample: 4.774 x 10-3M or 169.31 ppm Wt% NaCl in Celery Salt: 34.64%
In the experiment “ISE: The Determination of Chloride”, the sample of unknown: 34 was found to have a Chloride concentration of 52.12 ppm/0.0147 moles/L, and a Wt% of Cl- : 12.25%. In the development and use of the standard additions plot the concentration of a celery salt sample was determined. The concentration of the celery solution was found to be 169.31ppm/4.77 x 10-3 moles/L, and the Wt% of sample was 34.64% . In this experiment careful precision as well as accuracy, was avidly tried to be maintained throughout the entire experiment, however the possibility of systematic error may arise. An account for such error may be contributed by: 1.Inability of using the same analytical balance throughout the experiment; possibility of one balance giving a different reading than another. .
2.In potentiometric titrations with ISE electrodes, the activity of the solution will ultimately contribute in the determination of the known concentration. The possibility added activity via introduction of water may contribute to a falsely high concentration. Possible systematic errors that could have happened (not throughout my analysis however) if: a.After you dried your unknown, but before you were able to weigh it, you left it out of the desiccator and it picked up...