Objective: To explore the reason why the solution first turns red and then fades after the reaction of sodium peroxide with water. According to the analysis and speculation of peroxide (1)

(1) In the reaction equation of sodium peroxide and water, only sodium hydroxide and oxygen are produced, so we can only guess the cause of fading in three situations: oxygen has bleachability, sodium hydroxide has bleachability, and oxygen and sodium hydroxide have bleachability together; In the experiment 1, phenolphthalein was added to the sodium hydroxide solution to prove whether the fading was caused by sodium hydroxide, so the corresponding guess was b; In experiment 3, oxygen was introduced to prove that oxygen can change the color of the solution; In order to enhance persuasiveness and avoid interference, the sodium hydroxide solution in experiments 1 and 2 must be prepared with sodium hydroxide solid.

So the answer is: oxygen and sodium hydroxide are bleaching; b； a； Sodium hydroxide solid;

(2) During the reaction of sodium peroxide with water, sodium forms a stable compound, and other elements combine to form an unstable bleachable substance X, which can only be H 2 O 2 with strong oxidation.

So, the answer is: H2O2

(3) Hydrogen peroxide can decompose and release oxygen under the action of manganese dioxide as a catalyst. The purpose of the device in the figure is to explore the instability of hydrogen peroxide, so the material at ① is a mixed solution of sodium peroxide and water, and the material at ② is manganese dioxide as a catalyst.

So, the answer is: b; c；

(4) The gas ③ in the device is oxygen generated by the decomposition of hydrogen peroxide; Because the hydrogen peroxide generated by the reaction of sodium peroxide and water is unstable and has been decomposed to generate oxygen, hydrogen peroxide molecules are not written.

So, the answer is: O2; H 2 O 2 is unstable and has been decomposed.