E9
CONDUCTIVITY MEASUREMENTS
You are required to submit a report for this exercise. A report includes results, calculations and
questions.
PURPOSE
To calibrate a conductivity cell, and use it to measure the specific conductance of samples.
PROCEDURE
Calibration
1.
Calculate the mass of KCl required to prepare 250 mL of 0.01 M solution.
2.
Prepare 250 mL of exactly 0.0100 M KCl solution from dried KCl (your weighed mass must be
within 0.5 mg of the calculated exact mass).
3.
You will be shown how to read the Metrohm conductivity meter, which measures the
conductance (G) of the solution. Note the cell constant marked on the electrode body.
4.
Rinse a 150 mL beaker with some of the KCl solution, and rinse the cell by immersing it in the
KCl solution. Discard.
5.
Measure the conductance and the temperature of the solution.
Sample measurement
6.
Measure the conductance and temperature of:
•
tap water
•
distilled water
•
Throsby Creek water
•
quality control standard
•
0.01 M HCl
•
0.01 M NaOH
•
0.01 M NaCl
•
0.01 M CH3COOH
•
0.01 M NaCH3COO
CALCULATIONS
•
using the equation in your notes, calculate the temperature-corrected conductance for the
calibration standard, and each sample solution in step 6
•
using the table value for the specific conductance of 0.01 M KCl in your notes, calculate the
value of the cell constant (Cc)
•
calculate the % difference between your value for the cell constant and the manufacturer’s
•
using your value for Cc, calculate the specific conductance of the solutions in step 6
QUESTIONS
1.
Explain the differences in the conductances of the 0.01 M solutions measured in this exercise.
2.
Explain why conductivity is a good measure of water purity in applications such as boiler water
monitoring.
3.
Why is specific conductance the quoted measure when testing water for environmental license
reporting?
E9 - CONDUCTIVITY MEASUREMENTS
RESULTS SHEET
Quality control standard code
Cell constant
Solution
Measured Conductance
Temperature
0.01 M KCl standard
tap water
distilled water
Throsby creek water
QC standard
0.01 M HCl
0.01 M NaOH
0.01 M NaCl
0.01 M CH3COOH
0.01 M CH3COONa
Tester’s signature ________________________________
Date _______________
Supervisor’s signature ______________________________
Date ______________