(2006? Hebei) The experimental setup for determining the oxygen content in air is shown in the figure. Experimental steps are as follows: ① add a small amount of water in the cylinder, and do a good j

(2006? Hebei) The experimental setup for determining the oxygen content in air is shown in the figure. Experimental steps are as follows: ① add a small amount of water in the cylinder, and do a good job labeling! (1) red phosphorus combustion in oxygen to produce phosphorus pentoxide, the chemical equation of the reaction is: 4P + 5O2

? Ignite? .

?

2P2O5; so the answer is: 4P+5O2

? Ignite? .

?

2P2O5;

(2) The burning of red phosphorus consumes oxygen, and when the spring clip is opened, the water in the beaker enters the gas cylinder and accounts for about one-fifth of the cylinder's volume, so it can be proved that the oxygen accounts for about one-fifth of the total volume of air

1

5

;

(3) From the experimental phenomenon in (2) it can be concluded that The conclusion about the composition of air is that oxygen accounts for about one-fifth of the volume of air;

(4) Nitrogen does not burn or support combustion, and is not soluble in water;

(5) The experimental operation should pay attention to the following problems: the device should be airtight; red phosphorus should be enough; to cool down to room temperature and then open the spring clip, and so on.

Answer:

(1) 4P+5O2

? Ignite? .

?

2P2O5

(2) Water enters the cylinder and accounts for approximately

1

5

(3) Oxygen accounts for about one-fifth of the volume of air;

(4) It does not burn or support combustion, and is insoluble in water

(5) The device is air-tight to be good