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.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.