(2010?Changzhou) One of the experiments on the city's Chemistry Laboratory Operations Examination this year is "Oxygen Production from Potassium Permanganate". The following is an excerpt from a stude

(2010?Changzhou) One of the experiments on the city's Chemistry Laboratory Operations Examination this year is "Oxygen Production from Potassium Permanganate". The following is an excerpt from a student's experiment (1) According to the principle of the reaction in the laboratory with potassium permanganate to make oxygen can be known as the chemical equation of the reaction is: 2KMnO4

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K2MnO4+MnO2+O2↑;

So the answer is: 2KMnO4

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K2MnO4+MnO2+O2↑;

(2) According to the different roles of the three knobs on the iron frame table, based on the diagram, it can be seen that A can be adjusted to the entire height of the test tube, so choose A;

(3) According to the method of checking the airtightness of the device: Insert the catheter into the water and hold the test tube with your hand, if there are bubbles coming out of the mouth of the tube The rubber plug was not plugged tightly after adding the drug;

(4) According to the laboratory device for the production of oxygen, the operation steps, precautions:

Collection of oxygen by the drainage method: the catheter extends into the cylinder when collecting the gas is just over the mouth of the cylinder, because the air in the test tube is just starting to be discharged;? The cylinder is filled with water (there can be no bubbles) and then placed upside down into the sink; to wait until the bubbles are released continuously and uniformly, and then begin to collect, otherwise the collected oxygen is impure, mixed with air;

This shows that the steps in the question: ③ bubbles appeared at the bottom of the cylinder; ⑤ bubbles were produced at the mouth of the catheter, and then immediately collected with the cylinder; resulting in the collection of oxygen is impure; the correct method: ③ bottom of the cylinder Can not appear bubbles; ⑤ to wait until the bubbles are released continuously and evenly, and then start collecting, so the answer is: ③ ⑤;

(5) according to the experimental operation: even → check → load → set → point → collect → move → extinguish, and the precautions: after the experiment is completed, the catheter should be moved out of the water, and then extinguished after the alcohol lamp, to prevent the alcohol lamp because of extinguishing the alcohol lamp caused by the temperature in the test tube to decrease, resulting in the pressure inside the test tube decreased suddenly, the water in the sink along the catheter, the water in the water tube, and the alcohol lamp is not used for the collection of oxygen. The water in the sink enters the test tube along the conduit and makes the test tube explode; so the answer is: backsiphonage (or large test tube rupture)