Determination Of Chlorides

ISE: The Determination of Chloride

Unknown: #34

I. Purpose:

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.

II. Experimental Parameters:

A. Theoretical Equations

B. Standard Additions Method

III. Sample Calculations

A. Concentration of Chloride in the Calibration Solution

B. Calculation of Slope, Intercept and Equation of for the Calibration Line

i. LLS Table

ii. Calculations

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

A. Calibration Data

i. Calibration Graph

See Attached Graph Calibration Plot.

ii. Calibration DataTable

Data Points for Calibration Plot.

Log [Cl-] E (mV)

-1.2142 -1

-1.3579 8

-1.552 19

-1.7874 34

-2.0511 49

-2.2574 61

-2.7184 88

-3.0167 106

-3.4115 129

-3.7117 147

-3.9332 157

-4.1671 170

-4.41 194

-4.7109 194

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 Added Potential (mV) Y-Values

1.17(4) mL 62 mV 22.07(7) mL

5.01(2) mL 56 mV 28.36(2) mL

10.00(8) mL 50 mV 36.58(9) mL

Data

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