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I have magnesium ribbons, blue litmus paper, battery connected to a bulb and carbon...

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mansoor1 | eNotes Newbie

Posted August 25, 2013 at 2:32 PM via web

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I have magnesium ribbons, blue litmus paper, battery connected to a bulb and carbon electrodes, solid citric acid and solution of citric acid in propanone.
i gotta design an experiment to show that acids only exhibit acidic properties when dissolved in water. How could i do this?

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mvcdc | Student, Graduate | (Level 1) Associate Educator

Posted August 25, 2013 at 3:05 PM (Answer #1)

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The main objective is to show that acids only exhibit acidic properties when dissolved in water. An experiment should contain different variables. In this case, we only want to test acidic properties of acid and show that these only appear when the acid is in water. Hence, we need a set-up that contains acid dissolved in water. Next, to show that acids need to be DISSOLVED IN WATER, another set-up would be acid dissolved in propanone (to emphasize that the solvent needs to be water). Lastly, we use solid citric acid (to emphasize the id needs to be DISSOLVED). [Note: Solid acid emphasizes that the acid needs to be dissolved/solubilized, while acid in propanone emphasizes that the solvent should be water.]

After this, we only need to verify acidic properties. The following are the properties we need to verify:

  • Metals dissolved in acid will release hydrogen gas (bubbling is observed). We therefore expect that if the magnesium ribbon is added to acid in water, bubbles will be formed, whereas the bubbles (if any) won't be as evident in the propanone solution, and wouldn't react with the solid citric acid.
  • Acids turn blue litmus paper to red. The litmus paper will become red when added to the water solution, but not to the propanone solution. Placing the solid acid in the litmus paper shouldn't do anything.
  • When acids dissolve, they dissociate. Strong acids dissociate completely, while weak acids don't dissociate as much. Citric acid is weak, but we still expect an incomplete dissociation. This dissociation allows them to carry electrical charge, and hence conduct electricity (they are electrolytes!). Hence, if you create a circuit (submerge wirings in solution -- check if circuit is correct, of course), we expect the bulb to light up with the water solution only.

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