(20 13? Qujing), an inquiry learning group, uses the following improved device to explore the conditions of material combustion. Access to information ① White phosphorus is highly toxic.

(1) Mars is produced around the white phosphorus, and a large amount of white smoke is produced above the liquid surface, indicating that oxygen is produced, which proves that one of the conditions of combustion is contact with oxygen.

(2) The function of sodium hydroxide is to prevent phosphorus pentoxide produced by white phosphorus combustion from escaping and endangering human health;

(3)

guess

The substances involved in the reaction are Na2O2 and H2O. By analyzing their elemental composition, there are only three elements: Na, H and O. According to the law of conservation of mass, the product should also contain these three elements, so the other substance produced can only be sodium hydroxide, not Na2CO3.

Experimental demonstration

Phenolphthalein turns red when it meets alkaline solution. Now the colorless phenolphthalein test solution is dropped into the solution after the reaction, and it is found that the phenolphthalein test solution turns red, indicating that the solution obtained after the reaction is alkaline;

result expression

According to the experimental results, the substances generated after the reaction are sodium hydroxide and oxygen, and the equation is: 2na2o2+2h2o ═ 4 NaOH+O2 ↑;

Extension extension

Sodium peroxide solid reacts with carbon dioxide at room temperature to produce sodium carbonate and oxygen. The way to judge whether sodium peroxide is stored in a bottle of air for a long time is to add dilute hydrochloric acid. If bubbles are generated, it is proved to be deteriorated.

Answer:

(1) oxygen; Contact with oxygen

(2) It can prevent phosphorus pentoxide generated by white phosphorus combustion from escaping and endangering human health;

(3)

guess

There is no carbon element in the reaction substance.

Experimental demonstration

Experimental operation Experimental phenomena Experimental conclusion Take a small amount of sodium peroxide solid in a test tube, add enough water, and drop a small amount of colorless phenolphthalein test solution. The conjecture that phenolphthalein test solution turned red was expressed.

2Na2O2+2H2O═4NaOH+O2

Extension extension

Add dilute hydrochloric acid, and if bubbles appear, it proves deterioration.