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?

pink to colourless

Explanation:

In the ammonium hydroxide solution, the phenolphthalein will exist in its anion form due to the OH- concentration this has a pink colour. As ammonium chloride is added, the ammonium ion concentration increases far beyond the hydroxide ion concentration. The ammonium ions donate protons to the anionic form of phenolphthalein and the colour changes to colourless. The equilibrium involved is shown in the image attached.

< > according to newton's third law of motion, forces always act in equal but opposite pairs. another way of saying this is for every action, there is an equal but opposite reaction.< >