McqMate
| Q. |
A 'breath test' used by traffic police to check drunken driving uses: |
| A. | potassium dichromate-sulphuric acid |
| B. | potassium permanganate-sulphuric acid |
| C. | turmeric on filter paper |
| D. | silica gel coated with silver nitrate |
| Answer» A. potassium dichromate-sulphuric acid | |
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Explanation: The main constituent of alcohol is Ethanol and the concentration of ethanol in a sample can be determined by back titration with acidified potassium dichromate. Reacting the sample with an excess of potassium dichromate, all ethanol is oxidized to acetic acid. One major application for this reaction is in old police breathalyzer tests. When alcohol vapor makes contact with the yellow dichromate-coated crystals, the color changes from yellow to green. |
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