pH Meter
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A Description
A pH meter measures the pH of a solution utilizing a glass electrode.
The electrode is made of very thin glass that allows H+ ions to
pass through it. The meter measures electrical potential and converts
this data into a pH reading for a sample.
Calibrating the pH Meter
First, soak the glass electrode in distilled water for about
half an hour. Why?
Next, begin to calibrate the pH meter by setting it to read 7.00 in a buffer solution of pH = 7.00.
Video: Calibrating to pH 7 ( 1.89 M ) Text description
The meter should be calibrated with a basic solution if the sample to
be tested is basic or with an acidic solution if the sample is acidic. Continue to calibrate the meter
according to the pH of the sample to be measured.
Video: Calibrating to pH 4 ( 2.61 M ) Text description
Finally, rinse the electrode with pH = 7 solution and measure
the pH of this solution. If the meter does not read "7.00",
re-calibrate the instrument.
If the sample to be measured is basic, follow the same general
calibration procedure as used when the sample is acidic. In this
case, however, calibrate the meter using a pH = 10 buffer solution instead
of the pH = 4 buffer.
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Video ( 1.05 M ) |
In the video, the student calibrated the pH meter and placed it into a buffer solution of pH = 7. What should he do next? Answer |
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Video ( 1.85 M ) |
In the video, the student is attempting to calibrate the pH meter in a pH = 7 buffer solution. Describe her error. Answer |
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Using the pH Meter
After calibrating the instrument, first rinse the bulb with
distilled water and then with a portion of the sample to be tested.
Then measure the pH of the sample.
Video: Measuring the pH ( 2.61 M ) Text description
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List two reasons why a pH meter would be inappropriate to
use in order to measure the pH of a solution that is approximately
12 M NaOH. Answer
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Video ( 1.75 M ) |
In the video, the student is measuring the pH of an aqueous solution. Why is this pH measurement unreliable? Answer |
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