Preparation of various types of gases, general ideas and methods for producing gases

Nitrogen Lab NH4Cl + Nano2 == Heating == NaCl + N2 + 2H2O

Industrial separation of liquid empty.

General idea of preparing gases:

1. Find the reaction that generates the gas, and screen out a reasonable reaction as the reaction principle.

2. Select a reasonable reaction device, collection device and verification method according to the reaction principle and gas properties.

3. Design the operation steps for gas production and the treatment method of toxic tail gas.

Method of collecting gas when making gas:

1.Drainage method.

1) Insoluble or slightly soluble in water, and no chemical reaction with water.

can be collected by drainage.

2) Generally, the gas that can be collected by the drainage method should be used as much as possible, because the gas collected by the drainage method is of high purity, but contains a certain amount of water vapor.

2.Exhaust method.

1) It does not react with air, and the density is the same as the density of air.

Gases with large differences can be collected by the exhaust air method, relative to the molecular mass.

Gases greater than 29 are vented upward.

Collected, gases with a relative molecular mass of less than 29 are collected by the downward exhaust air method. The gas collected by the drainage method is purer.

2) The exhaust air collection method is characterized by simple operation, but the purity of the collected gas is not high.

Principle: CAC2+2H2O C2H2 +Ca(OH)2

Drug: CAC2: calcium carbide ion crystal commonly known as calcium carbide or disturbance, calcium carbide often contains calcium sulfide calcium arsenide calcium phosphide, they are combined with water to form H2S ash3 ph3 and other toxic odorous gases can be used with copper sulfate solution to remove impurities.

The use of calcium carbide in bulk form instead of powder form in the experiment is to slow down the reaction rate.

Saturated saline is often used instead of water in the experiment, the purpose is to slow down the reaction rate and obtain a stable acetylene gas flow The rate of acetylene formation can be controlled by adding water dropwise and the speed of saturated saturated saline.

Generator: Solid-liquid room temperature type Collect gas by draining method.

Procedures and precautions:

After assembling the device, check the air tightness first, then add calcium carbide, and then add saturated salt water drop by drop with a separating funnel.

When preparing acetylene, due to the violent reaction between calcium carbide and water and the formation of foam, if the test tube is used as a reactor, in order to prevent the foam from blocking the catheter, a small amount of cotton should be plugged at the mouth of the test tube.

This reaction cannot be used for the following reasons.

1. > reaction is violent and difficult to control.

2. > calcium carbide and water form powdery solids, which will block the lower mouth.

3. The reaction > violently exothermic and easy to burst the reactor.

Phenomenon Potassium permanganate solution fades Bromine's carbon tetrachloride solution fades Flame bright Thick black smoke.

Conclusion: Acetylene is reductive Acetylene can have addition reaction with bromine Acetylene is flammable.

As for your last question, it is safer to use a round-bottom flask due to the intensity of this experiment, but it is not necessary to use a test tube Erlenmeyer flask.

The test tube plus cotton has already been explained earlier.

This is my organic chemistry notes.,It's very complete.,The test center is basically in it.,The test center also has an electronic electronically for calcium carbide The air tightness inspection method of the device, etc.

There are generally two main methods of gas collection: the evacuation method and the drainage method

1. Emptying method: divided into upward emptying and downward emptying method, the upward emptying method is suitable for collecting gases with a density greater than air, and its principle is to use dense gases to squeeze out gases that are less dense than air, such as collecting carbon dioxide gas.

The downward emptying method is suitable for collecting gases with a density smaller than air, and the opposite of upward emptying, it is to use a gas with a density smaller than air to squeeze the air upward, such as the collection of hydrogen suitable instruments: alcohol lamps, iron frames, gas collection cylinders, wooden blocks, gas generating devices, etc., because it is to remove the air, so the collected air is not pure.

Therefore, it is generally only necessary to collect gases that are easily soluble in water, but it is easier to operate than the drainage gas collection method.

2. Drainage method: From the knowledge of physics, it can be seen that if a gas cylinder filled with a certain liquid is reversed (short in and long out), it is not soluble in the liquid and will not have a chemical reaction with the liquid. The liquid in it can be discharged and the container can be filled with the gas, according to which the gas can be collected directly by discharging some liquid by using the gas collection cylinder.

Advantages, the drainage gas collection method is a conventional method for collecting gas in the laboratory, which has the advantages of high purity, sufficient collection, no need to be full, less waste, and less pollution than the exhaust air method for gas collection.

The disadvantage is that this method also has a limited amount of gas that can be collected, and cannot collect gases that are soluble in water. The gas has disadvantages such as large water content and inconvenient operation.

Here's how to collect the gas:

1. Drainage and gas collection method.

A certain gas that is usually used for preparation is insoluble in water and can be collected by the drainage gas collection method. For example, potassium permanganate is pyrolytically decomposed to produce oxygen.

2. Upward air exhaust method.

It is usually used when the gas density is greater than the air (relative molecular mass is greater than 29) and does not react with the components in the air, and the upward air exhaust method can be used. For example, copper reacts with concentrated sulfuric acid to produce sulfur dioxide.

Sulfur dioxide has a relative molecular mass of 64, which is much larger than air and will sink.

3. Downward air exhaust method.

It is usually used when the gas density is less than air (relative molecular mass less than 29) and does not react with the components in the air, and the downward air exhaust method can be used. For example, if the relative molecular mass of ammonia is 17, which is much smaller than air and will float upward, the downward air exhaust method can be used.

A gas is a fluid that has no shape and volume that can be compressed and expanded. A gas is a state of matter. Gases are fluids like liquids:

It can flow and be deformable. Unlike liquids, gases have a large distance between their molecules and can be compressed and expanded. If there is no restriction (container or force field), the gas can expand without limiting its volume.

The atoms or molecules of gaseous matter can move freely with each other. The kinetic energy of atoms or molecules of gaseous substances is comparatively high. The form of a gas can be affected by its volume, temperature, and pressure. These elements make up a number of gas laws, and the three can influence each other.

There are many ways to collect gases. The common ones are the drainage method, the upward exhaust air method, and the downward exhaust air method. Different methods require the preparation of different instruments and materials, some methods require the preparation of partial chemicals, while taking into account the difference in density of the collected gases and air.

First of all, prepare a glass bottle and glass tube blind, if the collected gas is insoluble in water, you can prepare a basin of water, using the drainage gas collection method, for example: potassium permanganate heating decomposition to produce oxygen.

The upward air exhaust method is also to prepare glass bottles and glass tubes, and the gas to be collected in this method requires that the gas density is greater than that of air, and the relative molecular mass is greater than 29and does not react with components in the air.

The downward exhaust air method, after the above instruments have been prepared, is usually used to collect gases that are less dense than air and have a relative molecular weight of less than 29A gas that does not react with air components.

1. The drainage method is suitable for gases that are not easily soluble in water. For example, hydrogen, oxygen.

2. Upward air exhaust method, suitable for gases that are denser than air and soluble in water, such as carbon dioxide and chlorine.

3. Downward air exhaust method, suitable for gases that are less dense than air and soluble in water, such as ammonia.

If the density is greater than the air, the upward air exhaust method is used, the density is less than the air is used by the downward air exhaust method (all the air exhaust method cannot react with the components in the air), the insoluble water can be drained by the drainage method, and the chlorine gas is discharged with saturated salt water.

Upward exhaust air method, downward exhaust air method, and drainage gas collection method.

Unwanted polluting gases can be collected by devices such as balloons at the end of the device.

Unwanted flammable gases or identified flammable gases can ignite at the end of the device if the product does not pollute the environment.