2. you are given an unknown solution that is one of the following: 0.1 m hcl, 0.1 m h₂so₄, or 0.1 m h₃po₄…

2. you are given an unknown solution that is one of the following: 0.1 m hcl, 0.1 m h₂so₄, or 0.1 m h₃po₄. given only 0.1 m naoh, deionized water, phenolphthalein, and a few test tubes, describe how you would identify the unknown acid.

2. you are given an unknown solution that is one of the following: 0.1 m hcl, 0.1 m h₂so₄, or 0.1 m h₃po₄. given only 0.1 m naoh, deionized water, phenolphthalein, and a few test tubes, describe how you would identify the unknown acid.

Answer

Explanation:

Step1: Dilute the acids

Dilute each of the three acids (0.1 M HCl, 0.1 M H₂SO₄, 0.1 M H₃PO₄) with deionized water.

Step2: Add phenolphthalein to NaOH

Add a few drops of phenolphthalein to the 0.1 M NaOH solution. The solution will turn pink.

Step3: Titrate with unknown acid

Take the pink - colored NaOH solution in test tubes. Titrate each of the diluted unknown acid solutions (from Step1) against the NaOH solution (from Step2).

  • For HCl ($\text{HCl}+\text{NaOH}=\text{NaCl}+\text{H}_2\text{O}$), the mole ratio of acid to base is 1:1.
  • For H₂SO₄ ($\text{H}_2\text{SO}_4 + 2\text{NaOH}=\text{Na}_2\text{SO}_4+2\text{H}_2\text{O}$), the mole ratio of acid to base is 1:2.
  • For H₃PO₄ ($\text{H}_3\text{PO}_4+3\text{NaOH}=\text{Na}_3\text{PO}_4 + 3\text{H}_2\text{O}$), the mole ratio of acid to base is 1:3.

Since the concentrations of the acids and the base ($\text{NaOH}$) are the same (0.1 M), the volume of the acid required to neutralize a fixed volume of NaOH will be different. The acid that requires the least volume to neutralize the NaOH (i.e., make the pink color of phenolphthalein - NaOH solution disappear) is H₃PO₄ (because of the 1:3 mole ratio), the acid that requires an intermediate volume is H₂SO₄ (1:2 mole ratio), and the acid that requires the largest volume (for the same volume of NaOH) is HCl (1:1 mole ratio).

Answer:

Dilute the acids. Add phenolphthalein to NaOH (turns pink). Titrate each acid against NaOH. The volume of acid needed to neutralize NaOH (pink color disappearance) will identify the acid: least volume - H₃PO₄, intermediate - H₂SO₄, most volume - HCl.