(20 1 1? Xianning simulation) a chemical interest group conducted an experiment as shown in the figure when studying the chemical properties of alkali. (1) An experiment can prove that hydrochloric acid. At the beginning of (1), sodium hydroxide is alkaline and turns red when it meets phenolphthalein. Sodium hydroxide reacts with hydrochloric acid to produce sodium chloride and water. With the dropping of hydrochloric acid, the red color of the solution in the beaker gradually faded.

(2) When opening K 1, sodium hydroxide reacts with carbon dioxide to generate sodium carbonate and water, which reduces the pressure in the bottle. Under the action of atmospheric pressure, the balloon bulged. After K2 is opened, hydrochloric acid reacts with sodium carbonate generated by the reaction to generate carbon dioxide, which increases the pressure in the bottle and deflates the balloon again.

(3) Both reactions produce sodium chloride, so it must contain sodium chloride. Both sodium hydroxide and sodium carbonate are alkaline and can coexist. Calcium chloride+sodium carbonate = calcium carbonate ↓+sodium chloride. As can be seen from the image, adding calcium chloride solution will produce precipitation, and the waste liquid must contain sodium carbonate, not just sodium hydroxide. Whether it contains sodium hydroxide can be judged according to whether the solution of sodium carbonate is still red after complete reaction.

So the answer is: (1) With the dropping of hydrochloric acid, the red color of the solution in the beaker gradually fades;

(2) Carbon dioxide +2 sodium hydroxide = sodium carbonate+H2O; Bubbles are generated and balloons become smaller;

(3) sodium chloride; Sodium carbonate and sodium hydroxide; a； The red color of waste liquid fades; ? muriatic acid