How is nitrogen made in a laboratory


Gases are required in a variety of ways in the laboratory. Various processes can be considered for producing gases in schools. Difficult-to-melt test tubes, which are connected to a stopper and a drainage tube, serve their purpose for simple student exercises.




Thermal decomposition of solids


The test tube is clamped horizontally in a stand and carefully heated. Since oxygen is heavier than air, it is introduced into a vertical test tube with the opening facing upwards. In this way, oxygen can be produced by heating potassium permanganate to over 240 ° C (> student exercise):

10 KMnO4  3 K2MnO4 + 2 K2O • 7 MnO2 + 6 O2


name of Gas
formula
Manufacture by Heating of:
Made of 1 g of fabric arise at most:
oxygen
O2
Potassium permanganate
110 ml
ammonia
NH3
Mixture of ammonium chloride
and calcium hydroxide
150 ml
Hydrogen sulfide
H2S.
Mix 1 part by mass of paraffin and kieselguhr with 2 parts by mass of sulfur
225 ml
Nitrogen dioxide
NO2
Lead (II) nitrate
80 ml
Carbon monoxide
CO
Mix 2 parts by weight of zinc and 1 part by weight of calcium carbonate
not specified


Expelling gases from liquids by heating

If gases are dissolved in liquids, they can be expelled by simply heating them. As a rule, two round-bottom flasks made of Duran glass are used, a stopper with a gas discharge tube being placed on the lower flask. Careful heating fills the upper, inverted round-bottomed flask with the expelled gas. This apparatus is suitable, for example, for the production of hydrogen chloride or ammonia for fountain experiments:




The disadvantage of this method is the high moisture content of the expelled gases. They may therefore have to be dried (> drying gases). Two thick-walled test tubes placed one on top of the other are also suitable for student exercises, the lower one being heated in a water bath. It should be noted, however, that students are not allowed to work with concentrated acids.


name of Gas
formula
The production takes place by heating:
A maximum of 10 ml of liquid results in:
Hydrogen chloride
HCl
Smoking hydrochloric acid
700 ml
ammonia
NH3
Ammonia solution 10%
900 ml
Sulfur dioxide
SO2
sulphurous acid
225 ml



Gas development through chemical reaction with a liquid

A simple, unregulated gas generator consists of a reaction vessel, for example a round-bottom flask or an Erlenmeyer flask with a drain and an attached dropping funnel. The amount of liquid fed into the reaction vessel can be regulated via the tap. An interruption by closing the drain is not possible, since the container would then burst if it does not have pressure equalization.




Gas generator with test tubes
for simple student exercises
Ground joint gas generator with
Dropping funnel and pressure equalization
   
   
If poisonous or aggressive gases such as chlorine are produced, a grinding device must always be used. In addition, the gas development should be carried out in a well-pulling fume cupboard. The dripping speed and thus also the speed of gas development can be controlled with the tap on the gas generator.


Surname of the gas
formula
Dripped liquid
Submitted material
From 1 g of solid, a maximum of:
hydrogen
H2
Hydrochloric acid 10%
Zinc granulated
350 ml
oxygen
O2
Hydrogen peroxide
solution 10%
Manganese (IV) oxide
from 10 ml of H2O2
250 ml
nitrogen
N2
Sodium nitrite solution
Ammonium chloride solution
from 10 ml A.
250 ml
chlorine
Cl2
Hydrochloric acid conc.
Potassium permanganate
150 ml
Hydrogen chloride
HCl
Sulfuric acid conc.
(heat)
Sodium chloride
370 ml
Hydrogen bromide
HBr
Phosphoric acid conc.
(heat)
Potassium bromide
80 ml
Hydrogen sulfide
H2S.
Hydrochloric acid 10%
Ferrous sulfide
230 ml
ammonia
NH3
Caustic soda conc.
Ammonium chloride
400 ml
carbon dioxide
CO2
Hydrochloric acid 10%
Calcium carbonate
210 ml
Carbon monoxide
CO
Sulfuric acid conc.
Sodium formate
not specified
Sulfur dioxide
SO2
Sulfuric acid 20%
Sodium sulfite
55 ml
methane
CH4
warm water
(only small amounts)
Aluminum carbide
180 ml
Ethine
C.2H2
water
(only small amounts)
Calcium carbide
310 ml



The rate of gas evolution depends on several factors, including the rate of reaction. Hydrogen can also be easily produced by throwing granular calcium into water. Calcium hydroxide is formed with the formation of hydrogen (> student exercise):
  
Ca + 2H2O Ca (OH)2 + H2   
  
The best-known device for continuous gas development is the Kipp gas generator invented by the pharmacist Petrus Jacobus Kipp (1808–1864) in 1860. This works according to the following principle:

a) After filling in the solid (e.g. zinc granulated) and the liquid (e.g. hydrochloric acid) with the tap closed, the liquid in the lower container rises until the air above prevents it from rising further.
b) By opening the tap, air escapes first, so that the liquid rises again and reaches the middle container. As a result, the liquid reacts with the solid and a gas (for example hydrogen) is created.
c) When the tap is closed, the liquid is pushed back by the gas that is initially still generated, so that the development of gas stops again.




Kipp'scher gas generator for the continuous extraction of hydrogen


When working with a Kipp gas generator, there are a few safety considerations that must be observed. The stoppers should be greased with ground joint grease and secured with wire clamps so that they are not squeezed out by the gas produced. When producing hydrogen, the oxyhydrogen gas test must be carried out before the gas is ignited.