Question
(b) Susie used water as the selvent in this experiment. When she repeated the experiment with a different set of pens , it did not work. She then used ethanol instead of water. Suggest why the experiment worked with ethanol but not with water.
Answer
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Answer
The experiment worked with ethanol and not with water because the ink from the have non-polar components in their ink that are better dissolved with a non-polar solvent like ethanol and not a polar solvent like water.
Explanation
The key point in this question lies in the nature of solvents and compounds. Chemistry teaches us that "like dissolves like". This means a polar substance (like water) tends to dissolve other polar substances, and a nonpolar substance (like oil or ethanol) tends to dissolve other nonpolar substances. In this context, susie first used water—a polar solvent—to dissolve the ink from a set of pens. If it worked, then that suggests the solute (ink) was also polar or at least had ionic or polar components. However, when she tried it with a different set of pens (presumably with different ink formulation), water couldn't dissolve the ink. From the fact that ethanol worked as a solvent, not water, it's apparent that those inks were more non-polar.