Exploration activity - Sodium bicarbonate and hydrochloric acid react to produce sodium chloride, water and carbon dioxide. Therefore, you will see bubbles emerging from the Erlenmeyer flask and the balloon inflates. The chemical equation is NaHCO3+HCl=NaCl +H2O+CO2↑, the foaming principle of effervescent tablets when placed in water is the result of the reaction between baking soda and the citric acid in the ingredients.

So the answer is: a large number of bubbles are generated and the balloon expands, NaHCO3+HCl=NaCl+H2O+CO2↑. Citric acid.

Exploration Activity 2

Experimental conclusion According to the experimental phenomenon, it is inferred that NaHCO3 will decompose when heated to generate carbon dioxide, while Na2CO3 does not decompose when heated. Therefore, the above conjecture is wrong. The chemical equation of the reaction that turns clear limewater in beaker C into turbid is: Ca(OH)2+CO2═CaCO3↓+H2O.

Communication and Discussion II: Because sodium bicarbonate solution is also alkaline, it cannot be inferred that it must be sodium hydroxide based on the red color of phenolphthalein.

According to the solubility of substances, calcium ions can be used to identify carbonates, so calcium hydroxide solution can be added.

Expansion and Application

① Sodium bicarbonate is easy to decompose when heated, so the heating method can be used to remove Na2CO3 solid mixed with a small amount of NaHCO3.

② Since sodium bicarbonate is unstable, it must be sealed and placed in a cool place when stored.

So the answer is: Experimental conclusion carbon dioxide, wrong Ca(OH)2+CO2═CaCO3↓+H2O.

Communication and discussion Ⅱ. Aqueous solutions of sodium carbonate and sodium hydroxide are both alkaline and can turn phenolphthalein red.

Ca(OH)2．

Expansion and application

①C

②Moisture and sun protection.