Why do the gas collectors that collect oxygen be covered with glass sheets and placed upright on the

The reason why the molecular mass of oxygen is larger than the average value of the air, that is, the oxygen can be guaranteed not to overflow, but to be stable at the bottom of the bottle, and the glass sheet is naturally isolated from the air to ensure the purity of oxygen.

It is upright because the density of oxygen is higher than the average density of air, and the popular point is that it is heavier. The glass sheet is covered to prevent convection with air and to maintain the purity of oxygen.

The molecular weight of oxygen is 32 The average molecular weight of air is 29 So oxygen is heavier than air, so you have to put the bottle mouth up and cover the glass sheet, the main reason is that we are afraid that the air inside will be polluted instead of pure oxygen, we know that the small molecules in the air are constantly doing irregular Brownian motion, so even if they are heavier than the air, they will still run out of the bottle... In this way, the air from the outside enters ·· The oxygen inside is polluted and no longer pure

The reason for standing is that the oxygen density is high and prevents it from escaping. The lid glass prevents other gases from entering the bottle. Affects purity.

Because oxygen is slightly denser than air.

For gases with a greater density than air, the gas collector cylinder should be placed positively;

If the density is less than air, the gas collector cylinder should be placed upside down.

Oxygen is one of the components of air and is colorless, odorless, and tasteless. Oxygen is heavier than air, has a density of grams in the standard condition (0 and atmospheric pressure 101325 Pa), and is soluble in water, but with very little solubility.

Since the density of oxygen is greater than that of air, the oxygen is transferred to the underside of the air, and the gas collector cylinder is placed upside down, and the gas collector cylinder cannot collect the slightest oxygen; When the cylinder is placed upright, the oxygen sinks to the bottom of the cylinder and the air is transferred over the oxygen until the oxygen fills the cylinder.

There are three commonly used methods of gas collection:

a. Upward air exhaust method: the gas density is greater than that of air (relative molecular mass is greater than 29) and does not react with the components in the air can be collected by the upward air exhaust method (Figure 1 below);

b. Downward air exhaust method: the gas density is less than that of air (relative molecular mass less than 29) and does not react with the components in the air can be collected by the downward air exhaust method (Figure 2 below);

cDrainage method: suitable for difficult or insoluble gases that do not react with water, and the catheter is slightly extended into the bottle (as shown in Figure 3 below); <

If the gas to be collected is toxic and soluble in water, you can use the following diagram:

1) If the density of the gas is greater than that of air, it enters through port A;

2) If the density of the gas is less than that of air, it enters through port B;

<>3) If the density of the gas is greater than that of air, it enters through port B;

4) If the density of the gas is less than that of air, it enters through port A;

Gas incoming from port B: An inverted funnel or dryer can be used to prevent sucking.

Regardless of whether it is the upward or downward exhaust method, the air in the cylinder can only be removed from the bottom by going deep into the bottom of the cylinder.

If you put the air trap at the mouth of the bottle, it can also be collected, but in this way, a larger part of the oxygen will run out, and if you go deep into the bottom of the cylinder, the denser oxygen will squeeze the air away, and it will rarely run out of itself, so it will be collected faster.

First of all, the mouth of the gas collector cylinder is frosted (this is also the only place where the gas collector cylinder is different from the jar, the inner wall of the jar is frosted. Therefore, the glass sheets used in the gas collection cylinders are ground glass sheets, that is, frosted. First exclude.

O2—The matte side is facing up"This is also not right, the frosted side is facing up, that is, the mouth of the gas collection cylinder is facing down, and the oxygen density is greater than the air density, so it should be collected by the upward exhaust air method, and the bottle mouth is facing up. "CH4 — Matte side up"This correct CH4 density is less than air meters, so it is collected by the downward exhaust air method, with the mouth of the gas collector bottle facing downwards and the frosted side of the glass sheet facing upwards.

i f u you didn't say it earlier.

1 and 4 are definitely not true. (The downward exhaust method should be used, and it should be reversed) All that remains is 2 and 3 2 pairs of frosted sides should touch the gas collector cylinder.

Precautions for use:

Cannot be used for heating. If the substance and gas are exothermic reactions, an appropriate amount of water or a layer of sand should be placed in the gas collection cylinder.

The main method of gas gathering in this paragraph:

The method of collecting gas is divided into the drainage method, the upward air exhaust method and the downward air exhaust method.

The drainage method now fills the gas collection cylinder with water and buckles it upside down in the water tank, inserts the conduit into the gas collection cylinder, and covers the ground glass sheet and takes it out after the water in the bottle is fully emptied.

Only suitable for gases that are insoluble in water or slightly soluble in water.

Upward exhaust air method.

Now place the mouth of the dry and clean empty gas collector cylinder on the experimental table, and extend the catheter into the bottom of the gas collector cylinder to start collecting gas. After a period of time, a full test can be performed:

Oxygen: Put the wooden strip (match) with sparks on the mouth of the bottle, if the wooden strip (match) is rekindled, it means that the oxygen in the bottle is full;

Carbon dioxide: Put a wooden stick (match) with a flame on the mouth of the bottle, if the wooden stick (match) is extinguished, it means that the carbon dioxide in the bottle is full;

The upward air exhaust method is generally used to collect gases that are easily soluble in water or will chemically react with water, and the density of the gas must be greater than that of air; Not suitable for gas collection that reacts with substances in the air or is less dense than air.

Downward exhaust air method.

The downward exhaust air method is used to collect gases that are less dense than air, such as hydrogen.

Purpose of this paragraph:

It is used to collect or store small amounts of gas.

Satisfied with the answer. Enthusiastic to ask friends.

2011-08-01Oxygen density is a little greater than air, so it should be square, and cover it to prevent gas impurity.

Follow-up question: Why is it necessary to put it forward when the density is a little higher than the air?

Otherwise, the oxygen will escape.

Follow-up: Can't you play it upside down? Still don't get it.

No, if you put it upside down, the oxygen will run out.

Follow-up: It's not a piece of glass.

It's useless, it's the rules for producing oxygen.

Follow-up: I still don't understand.

Anyway, no gas cylinder can be put upside down.

Follow-up: Hydrogen is OK, and NH3 is available

When it is full, it is necessary to put it up, and when it is collected, hydrogen and ammonia must be collected by the blind air method.

Follow-up: The book says that NH3 and hydrogen should be reversed.

Oh yes, the oxygen is really being put on anyway.

Follow-up question: But why, although I know that the density is greater than the air, it seems that it will not affect the forward or backward release.

Yes, there's pressure.

Follow-up: Mainly embodied in **?

The oxygen in the bottle is more pressurized than the oxygen in the outside world.

Follow-up: What about the positive release?

It's okay to put it on!

Follow-up: Understood.

There are mainly 1Upward exhaust air method. 2. Downward exhaust air method.

3. Drainage method. The air exhaust method is determined according to the density of the gas to be collected (the relative molecular mass is 29 and the average relative molecular weight of the air is 29 to know the weight by comparing the size).That is, if the density is greater than the air (gas sinking), the upward air exhaust method is used, and after it is full, it is covered with a glass sheet and squared on the table.

Because of the high density, that is, sinking, if the bottle mouth is downward, the gas will escape from the gap between the bottle mouth and the glass sheet).If the density is smaller than the air (gas floating), the downward air discharge method is used, and after it is full, the glass sheet is covered and placed upside down on the table (because the density is small, the gas floats upward, and if the bottle mouth is upward, the gas will escape from the gap between the bottle mouth and the glass sheet).If the gas is not soluble or insoluble in water, the drainage method can also be used (this method can collect the purer gas).

Whether to put it upside down or upside down on the desktop after collection, the principle is the same as above. Hope you can see it.