In part iii, the phenolphthalein indicator is used to monitor the equilibrium shifts of the ammonia/ammonium ion system. the phenolphthalein equilibrium established with water is hph(aq)(colorless) + h2o (l) h3o+ (aq) + ph-(aq)(pink or red). you compared the color of the solutions in three test tubes that initially contained 3 ml of 0.1 m ammonium hydroxide and a few drops of phenolphthalein indicator. in the first test tube, you added 1 m nh4cl dropwise. what color change was observed and what did this color change indicate about the shift in the phenolphthalein equilibrium? a. the solution turned a more intense pink or red color indicating that the phenolphthalein equilibrium shifted to the left, producing more of the pink or red colored hph.

The pink color in the solution fades. Some of the colored indicator ion converts to the colorless indicator molecule.

What's the initial color of the solution?

is a salt soluble in water. dissociates into ions completely when dissolved.

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The first test tube used to contain . is a weak base that dissociates partially in water.

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There's also an equilibrium between and ions.

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ions from will shift the equilibrium between and to the right and reduce the amount of in the solution.

The indicator equilibrium will shift to the right to produce more ions along with the colored indicator ions. The solution will show a pink color.

What's the color of the solution after adding NH₄Cl?

Adding will add to the concentration of ions in the solution. Some of the ions will combine with ions to produce .

The equilibrium between   and ions will shift to the left to produce more of both ions.

The indicator equilibrium will shift to the left as the concentration of increases. There will be less colored ions and more colorless molecules in the test tube. The pink color will fade.