Properties of lithium, and the reactions of water and certain acids with lithium

In 1817, a met­al of the first group of the sec­ond pe­ri­od in the pe­ri­od­ic ta­ble was dis­cov­ered – lithi­um. The dis­cov­ery was made by the Swedish sci­en­tist Jo­hann Au­gust Ar­fwed­son, who was in­ves­ti­gat­ing var­i­ous min­er­als. The el­e­ment was found in petal­ite, spo­dumene and lep­i­do­lite. Short­ly af­ter­wards, in 1818, metal­lic lithi­um was ob­tained by Humphrey Davy.

Lithi­um and its com­pounds are es­sen­tial chem­i­cal el­e­ments in the life of hu­man be­ings, and are used in many spheres of in­dus­try:

• in the man­u­fac­ture of chem­i­cal sources of elec­tri­cal en­er­gy;
• in the man­u­fac­ture of fire­works: lithi­um ni­trate turns flames red;

• lithi­um is of­ten used as a met­al for al­loys, mak­ing it pos­si­ble to cre­ate light but durable sol­ders;

• lithi­um is also used in ra­dio elec­tron­ics and nu­cle­ar en­er­gy;

• lithi­um salts are wide­ly used in medicine. Lithi­um is vi­tal for hu­man health in small amounts, and takes part in the func­tion­ing of vi­tal or­gans such as the heart, liv­er and lungs.

This is far from all the spheres where this met­al and its com­pounds are used.

Phys­i­cal prop­er­ties of lithi­um

Lithi­um is an al­ka­line met­al of a sil­very-white col­or. It is soft and eas­i­ly mold­ed, and a cube of metal­lic lithi­um can be cut with a knife.

It is in­ter­est­ing that lithi­um is the only met­al from this group which boils and melts at rather high tem­per­a­tures: 1340 and 180.54 de­grees Cel­sius re­spec­tive­ly. But it is also in­ter­est­ing that com­pared with its “al­ka­line neigh­bors”, lithi­um has the low­est den­si­ty – half the den­si­ty of wa­ter. This prop­er­ty means that lithi­um does not even sink in kerosene.

Chem­i­cal prop­er­ties

Lithi­um is clas­si­fied in the al­ka­line group of met­als, but it be­haves sta­bly in air and prac­ti­cal­ly does not in­ter­act with oxy­gen, not even dry oxy­gen. Ow­ing to the un­usu­al prop­er­ties of this met­al, un­like oth­er al­ka­line met­als it is not stored in kerosene, es­pe­cial­ly as its low den­si­ty means that it will float. Lithi­um should be stored in paraf­fin, pe­tro­le­um ether, gaso­line or min­er­al oil in a her­met­ic met­al con­tain­er.

In hu­mid air, lithi­um may en­ter into slow re­ac­tions with ni­tro­gen and oth­er gas­es con­tained in air. Li₃N, LiOH и Li₂­CO₃ — lithi­um ni­tride, hy­drox­ide and car­bon­ate — form.

Oth­er chem­i­cal prop­er­ties of lithi­um

When heat­ed with oxy­gen, lithi­um burns with the for­ma­tion of lithi­um ox­ide Li₂O.

Lithi­um and its salts turn flames a carmine red col­or.

This qual­i­ta­tive re­ac­tion for lithi­um was es­tab­lished by Leopold Gmelin in 1818.

At tem­per­a­tures from 100 to 300 de­grees Cel­sius, a dense ox­ide film forms on the sur­face of lithi­um, which pro­tects the met­al from fur­ther ox­i­da­tion. It eas­i­ly re­acts with halo­gens, with the ex­cep­tion of io­dine.

Lithi­um re­acts calm­ly with wa­ter: the re­ac­tion is not ac­com­pa­nied by com­bus­tion or an ex­plo­sion.

Lithi­um in­ter­acts with al­co­hols, form­ing al­co­ho­lates

When heat­ed it re­acts with sul­fur, sil­i­con, io­dine and hy­dro­gen, form­ing lithi­um sul­fide, sili­cide, io­dide and hy­dride re­spec­tive­ly.

Re­ac­tion of lithi­um with wa­ter

The re­ac­tion takes place quite calm­ly. Like all al­ka­line met­als, if lithi­um is placed in wa­ter, an al­ka­li be­gins to form, and hy­dro­gen is re­leased, and the met­al floats on the sur­face and lit­er­al­ly melts be­fore your eyes. The re­ac­tion of the dis­so­lu­tion of lithi­um in wa­ter is ac­com­pa­nied by a char­ac­ter­is­tic hiss­ing.

The al­ka­li that forms in the so­lu­tion is called lithi­um hy­drox­ide LiOH, which con­sists of white crys­tals, and is quite a strong base:

2Li + 2H₂O → 2LiOH + H₂↑

Re­ac­tion of lithi­um and sul­fu­ric acid

If a small piece of lithi­um is added to con­cen­trat­ed sul­fu­ric acid, lithi­um sul­fate, hy­dro­gen sul­fide and wa­ter form.

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This re­ac­tion is dan­ger­ous, es­pe­cial­ly at home, as lithi­um im­me­di­ate­ly burns with a bright flame:

8Li + 5H₂­SO₄ → 4Li₂­SO₄ + Н₂S + 4H₂O

With di­lut­ed sul­fu­ric acid, lithi­um in­ter­acts with the for­ma­tion of lithi­um sul­fate and hy­dro­gen.

2Li + H₂­SO₄ → Li₂­SO₄ + Н₂

Re­ac­tion of lithi­um with ni­tric acid

If a piece of lithi­um is placed in di­lut­ed ni­tric acid, lithi­um ni­trate, am­mo­ni­um ni­trate and wa­ter form:

8Li + 10H­NO₃ → 8Li­NO₃ + NH₄NO₃ + 3H₂O

With con­cen­trat­ed ni­tric acid, lithi­um re­acts dif­fer­ent­ly, and the prod­ucts of re­ac­tion will be lithi­um ni­trate, wa­ter and ni­tric diox­ide.

Li + 2H­NO₃ → LiNO₃ +NO₂ + H₂O

Re­ac­tion with hy­drochlo­ric acid

With hy­drochlo­ric acid, lithi­um re­acts like oth­er met­als, form­ing lithi­um chlo­ride and hy­dro­gen.

2Li + 2HCl = 2Li­Cl + H₂

We should note that the re­ac­tion of lithi­um and oth­er al­ka­line met­als with acids takes place in a com­plex man­ner, as the acid so­lu­tions con­tain wa­ter, with which lithi­um ac­tive­ly in­ter­acts with the for­ma­tion of lithi­um hy­drox­ide, which en­ters into a re­ac­tion with acids with the for­ma­tion of salt and wa­ter.