Which of the following sets comprises liquids which are poor conductors of…
2021
Which of the following sets comprises liquids which are poor conductors of electricity?
- A.
tap water, shampoo, honey
- B.
salt solution, lemon juice, vinegar
- C.
shampoo, vegetable oil, distilled water
- D.
sugar solution, vinegar, lemon juice
Show answer & explanation
Correct answer: C
Electrical conductivity in a liquid, as judged by the standard school-level conductivity test (a battery-and-bulb/LED tester), depends on the presence of freely moving ions. Strong electrolytes (salts, strong acids, strong bases) dissociate almost completely and light the tester brightly; weak acids ionize only partially but still release enough ions to light it noticeably; liquids that release very few or no free ions under this test — non-polar substances, sugars, purified water, and other liquids that do not ionize appreciably — are classed as poor conductors.
Liquid | Conductivity in the standard test (and why) |
|---|---|
Tap water | Conducts weakly to moderately — contains dissolved mineral salts that release ions |
Salt solution | Conducts strongly — sodium chloride fully dissociates into ions in water |
Lemon juice | Conducts well — citric acid is a weak acid that ionizes only partially, but releases enough ions to carry current |
Vinegar | Conducts well — acetic acid is a weak acid that ionizes only partially, but releases enough ions to carry current |
Sugar solution | Conducts poorly — sugar dissolves as neutral molecules and does not ionize |
Shampoo | Conducts only weakly in this test — it does not ionize/release ions as effectively as a true electrolyte solution |
Vegetable oil | Conducts poorly, practically a non-conductor — non-polar, so it has no free ions |
Distilled water | Conducts poorly, practically a non-conductor — free of dissolved salts, so it has almost no ions |
Honey | Conducts poorly — made mainly of neutral sugar molecules |
The set of tap water, shampoo, and honey includes tap water, which contains dissolved mineral salts and so conducts electricity to a noticeable degree rather than being a poor conductor — the set does not fit the description.
The set of salt solution, lemon juice, and vinegar pairs a fully dissociating salt with two weak acids that still ionize enough to conduct well, so this trio conducts electricity well, the opposite of what is asked.
The set of sugar solution, vinegar, and lemon juice pairs one poor conductor with two weak acids that ionize enough to conduct well, so it is not a uniformly poor-conducting set either.
Only the set made up of shampoo, vegetable oil, and distilled water consists entirely of liquids that fail to release enough free ions to conduct electricity well in this test, so it is the correct set of poor conductors.