Methods for obtaining oxygen

Oxy­gen is a gas with­out taste, smell or col­or. It is the sec­ond most com­mon gas on the plan­et af­ter hy­dro­gen. It is a strong ox­i­diz­ing agent and a chem­i­cal­ly ac­tive non-met­al. This gas was dis­cov­ered by sev­er­al sci­en­tists at the same time in the 18th cen­tu­ry, and the first sci­en­tist to ob­tain oxy­gen was the Swedish chemist Scheele in 1772. The French chemist Lavoisi­er con­duct­ed re­search into the el­e­ment, and gave it the name of "oxygène". You can de­tect oxy­gen with a smol­der­ing piece of wood, which flares up bright­ly on con­tact with the gas.

The im­por­tance of oxy­gen

This gas par­tic­i­pates in com­bus­tion pro­cess­es, and oxy­gen is pro­cessed by green plants, which car­ry out the process of pho­to­syn­the­sis with their leaves, en­rich­ing the at­mos­phere with gas that is vi­tal for life.

How can we ob­tain oxy­gen? The gas is ob­tained from the air by in­dus­tri­al meth­ods, in which the air is pu­ri­fied and com­pressed. Our plan­et has enor­mous sup­plies of wa­ter, the chem­i­cal com­po­si­tion of which par­tial­ly con­sists of oxy­gen. This means that the gas can be ob­tained by break­ing down wa­ter. We can do this at home.

How to ob­tain oxy­gen from wa­ter

The fol­low­ing tools and ma­te­ri­als are re­quired for the ex­per­i­ment

• wa­ter;

• elec­tric­i­ty source;

• 2 plas­tic cups;

• 2 elec­trodes;

• Gal­van­ic bath.

Let’s ex­am­ine the process. Pour wa­ter into a gal­van­ic bath un­til it is over half full, and add 2 ml of caus­tic ni­trate or di­lut­ed sul­fu­ric acid – this in­creas­es the elec­tri­cal con­duc­tiv­i­ty of the wa­ter. Make holes at the bot­tom of the plas­tic cups, and pull elec­trodes through the holes – car­bon plates. We must iso­late the air lay­er be­tween the cup and the plate. We place the cups in the bath so that the elec­trodes are in the wa­ter, and the cups are up­side down. Be­tween the wa­ter sur­face and the bot­tom of the cup, there should be a min­i­mum of air.

We sol­der a met­al wire to each elec­trode, and con­nect them to the elec­tric­i­ty source. The elec­trode con­nect­ed to the neg­a­tive pole is called the cath­ode, and the one con­nect­ed to the pos­i­tive pole is the an­ode.

An elec­tric cur­rent pass­es through the wa­ter – elec­trol­y­sis of the wa­ter is car­ried out.

A chem­i­cal re­ac­tion takes place, form­ing two gas­es. Hy­dro­gen col­lects in the cup with the cath­ode, and oxy­gen in the cup with the an­ode. We de­ter­mine that gas has formed in the cups with the elec­trodes by the bub­bles of air that rise out of the wa­ter. Through a pipe we draw the oxy­gen out of the cup into an­oth­er con­tain­er.

Safe­ty rules

The chem­i­cal ex­per­i­ment to ex­tract oxy­gen from wa­ter should only be car­ried out ob­serv­ing safe­ty rules. The gas­es ob­tained in the process of wa­ter elec­trol­y­sis must be mixed. The hy­dro­gen ob­tained should not come into con­tact with the air be­cause of its ex­plo­sive na­ture. For safe and in­ter­est­ing ex­per­i­ments with dif­fer­ent gas­es click here.

How to ob­tain oxy­gen by the lab­o­ra­to­ry method

First method: pour cal­ci­um per­man­ganate into a test tube, and put the test tube over a burn­er. The man­ganese crys­tal heat up, and oxy­gen is re­leased. We catch the gas with a gas bath. Re­sult: 10 g of cal­ci­um per­man­ganate re­leas­es 1 l of oxy­gen.

Sec­ond method: we pour 5 g of ni­trate into a test tube, and seal the test tube with a fire-re­sis­tant cork with a glass pipe in it. We hold the test tube in place on a stand, and place a bath with sand un­der it, to avoid ex­ces­sive heat­ing. We turn on the gas burn­er and di­rect the flame at the test tube. The sub­stance melts, and oxy­gen is re­leased. We col­lect the gas through the glass tube in a bal­loon placed over it.

Third method: we pour potas­si­um chlo­rate into a test tube and place the test tube on a gas burn­er, af­ter seal­ing it with a fire-proof cork with a glass tube in it. The potas­si­um chlo­rate re­leas­es oxy­gen in the process of heat­ing. We col­lect the gas through the pipe in a bal­loon placed over it.

Fourth method: we hold a test tube in place with a stand, and pour hy­dro­gen per­ox­ide into the test tube – the un­sta­ble com­pound breaks down into oxy­gen and wa­ter on con­tact with air. To ac­cel­er­ate the re­ac­tion of the re­lease of oxy­gen, we add ac­tive char­coal to the test tube. We seal the test tube with a fire­proof cork with a glass pipe in it, place a bal­loon over the pipe and col­lect the oxy­gen.

You can or­der a month­ly sub­scrip­tion with cool sci­ence ex­per­i­ments kits for kids.