When cleaning up the laboratory after a science lesson, Lily found three unlabelled beakers containing colourless liquids on a benchtop. The class had just been working with acids and one group had forgotten to clean up. One beaker contained distilled water, another one contained dilute hydrochloric acid (HCl) and the third beaker contained dilute acetic acid (CH3COOH).
Design an experiment for Lily to correctly identify the liquids. Your answer must include the following:
A hypothesis with correct scientific reasoning.
A logical, complete and safe procedure to be followed, in which you have applied the most suitable property of acids in solution.
Type your answer in the space below:
Hypothesis:
If
then
because
Procedure:
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Lily can easily do a pH paper test to distinguish between them.
- She just knew that the three chemicals or liquids are water, hydrochloric acid and acetic acid.
- She can bring up some pH paper strips to dip in the liquids and can easily distinguish between the chemicals through their pH values.
- When dipped in the first liquid, she found out that there is a change of colour to green and found out that the pH is 7 which is neutral. Thus, it came out to be water.
- When dipped in the second liquid, the pH paper changed its colour into an orangish-yellow and the pH for this colour is 2 to 3 and it came out to be hydrochloric acid.
- The last liquid left has to be acetic acid, but she did so as to confirm it.
- The paper turned into greenish-yellow colour which shows a value of 4. Thus, the liquids were identified by pH paper test.
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