What is the best method to collect nitrogen, and what are the methods of collecting nitrogen?

In general, there are two common ways to collect gas:

Drainage method. : Air exhaust method (including upward evacuation method and downward evacuation method) and the density of nitrogen is approximately that of air (the relative molecular weight of nitrogen is 28, and the average relative molecular weight of air is 29).

Therefore, the evacuation method does not work, and the nitrogen received in this way is not pure.

Nitrogen, on the other hand, is poorly soluble in water, so it can be collected by drainage.

There are many ways to obtain nitrogen in the laboratory, and the 3 common methods are:

Method 1: Ammonia gas is passed into the hot copper oxide powder to obtain pure nitrogen and copper;

Method 2: Pass the air through the hot copper to obtain purer nitrogen and copper oxide powder;

Method 3: The mixed solution of sodium nitrite (nano2) and ammonium chloride is heated, and all nitrogen elements are converted into nitrogen.

The experimental instruments that can be selected for the experiment are shown in the following figure (the clamping device and heating device are omitted).

1) Method 1: The ammonia required for nitrogen production can be obtained by adding concentrated ammonia droplets to quicklime, and the generator of this reaction is best to choose the optional device number). Please write about the two roles of birth lime in this reaction:

2) Method 2: In order to ensure that the obtained nitrogen is as pure as possible, in addition to using copper, it can also be directed to the device

Optional device number) to remove other impurity gases.

3) Method 3: The chemical equation for nitrogen production is:

4) Green chemistry refers to the efficient use of (preferably renewable) raw materials, the elimination of waste and the avoidance of toxic and dangerous reagents and solvents in the manufacture and application of chemical products. Among the three methods for producing nitrogen, the combined method and method 2 have many advantages over method 3 alone, so please evaluate them from the perspective of green chemistry

5) In 1892, the British scientist Rayleigh discovered that the nitrogen obtained by method 2 was always denser than that obtained by method 3 under the same conditions5. If there are no errors in the design and operation of the above experiments, and the nitrogen is completely dry, please explain the reason for this phenomenon

Answers to test questions. Answer].

1）d；CAO reacts with water, reducing solvents; CAO reacts with water to release heat, reducing the solubility of ammonia.

2) e soda lime.

3）nano2+nh4cl nacl+n2↑+2h2o；

4) CU and CUO can be recycled to save reagents.

1.Evaporative condensation collection: It is collected by expelling air into a vacuum container to evaporate the nitrogen in the air. This method can effectively separate the nitrogen in the air, but it is less efficient, and in general, only a small amount of nitrogen can be collected from a large amount of air.

2.Liquid capillary absorption set: Liquid capillary absorption set is an advanced nitrogen collection method, which mixes the air to be collected with a certain concentration of liquid, and sucks the nitrogen in the air into the liquid through the action of the capillary, so that it is mixed into a solution with a certain degree of concentration, and then the mixture is condensed and separated to obtain the required nitrogen.

This method has the advantages of high efficiency, low energy consumption, low cost and less waste, and is one of the commonly used nitrogen collection methods.

Nitrogen and oxygen separation method Nitrogen and oxygen separation method is a method to effectively separate a large amount of nitrogen, which fills the air to be treated into a vacuum container, and then makes the oxygen and nitrogen molecules react by adding a solid adsorbent or a solid catalyst in the failure, so that the nitrogen molecules are adsorbed on the adsorbent, and the oxygen is absorbed by the reactants, and finally the nitrogen molecules adsorbed in the adsorbent are evaporated through the vacuum pump to obtain the required large amount of nitrogen.

Preparation method of nitrogen:

1. Cryogenic air separation nitrogen production: It is a traditional air separation technology with a history of more than 100 years. It is characterized by large gas production and high nitrogen purity of the product, and can produce more high-purity nitrogen without repurification.

However, its process flow is complex, covers a large area, the infrastructure cost is high, it requires special maintenance forces, there are many operators, it takes 18-24h to start each time, and the gas production is slow.

At standard atmospheric pressure, when cooled to a point where it becomes a colorless liquid, when it is cooled to a point where liquid nitrogen becomes a snow-like solid. It is suitable for large-scale industrial nitrogen production, and the cost of nitrogen is high.

2. Membrane separation nitrogen production: Membrane separation air separation nitrogen production is also a non-low-temperature nitrogen production technology, which is a new nitrogen production method rapidly developed abroad in the 80s, and it has been popularized and applied in China in recent years.

Membrane separation nitrogen production is to use air as raw material, under a certain pressure, using the different permeation rates of oxygen and nitrogen in the hollow fiber membrane to separate oxygen and nitrogen to produce nitrogen.

Compared with the above-mentioned nitrogen production methods, it has the characteristics of simple equipment structure, small size, no switching valve, easier operation and maintenance, faster gas production (less than 3min), and more convenient capacity increase, but the hollow fiber membrane has stricter requirements for compressed air cleanliness, and the membrane is easy to age and fail, difficult to repair, and needs to be replaced with a new membrane.

Membrane separation nitrogen production is more suitable for small and medium-sized users with nitrogen purity requirements of about 98%. When the purity of nitrogen is required to be higher than 98%, it is about 30% higher than that of the same type of pressure swing adsorption nitrogen generator.

3. Pressure swing adsorption nitrogen production (pressure swing adsorption, English translation as pressure swing adsorption, referred to as PSA): gas separation technology is an important branch of non-low temperature gas separation technology, which is the result of people's long-term efforts to find a simpler air separation method than cryogenic method.

Nitrogen production is based on air as raw material, using carbon molecular sieve as adsorbent, using carbon molecular sieve to select the adsorption of oxygen and nitrogen in the air of the land code cavity characteristics, at room temperature, pressure adsorption, decompression desorption, so that oxygen and nitrogen are separated, so as to produce nitrogen. Pressure swing adsorption nitrogen generator equipment is required.

Direct air fractionation is an industrial extraction method. If you want to extract nitrogen in the laboratory, you need to mix the ammonium chloride saturated solution with sodium nitrite solid and heat it. The nitrogen extracted in this way is mixed with water vapor, which can be removed in another container with desiccants such as concentrated sulfuric acid, soda lime, calcium oxide, anhydrous calcium chloride, anhydrous magnesium sulfate, etc.

For the specific chemical reaction equation, please trim it yourself:

Ammonium chloride + sodium nitrite = = sodium chloride + water + nitrogen.

Due to the influence of impurities in the reaction, the solution may turn yellow or even black; Nitrogen is not produced slowly and can be heated using a boiling water bath.

It can be made into chemical fertilizer to make protective gas to fill food packaging bags and extend the shelf life.

It's too much, let's see if your use is satisfied!