Reaction between copper sulfate and iron

What can you see when iron reacts with copper sulfate?

Copper sulfate crystals [Wikimedia]

Iron is an el­e­ment of the eighth group of the fourth pe­ri­od in the Pe­ri­od­ic Ta­ble. It is a mal­leable sil­very met­al with good elec­tro­con­duc­tiv­i­ty and pro­nounced mag­net­ic prop­er­ties. In na­ture iron is main­ly en­coun­tered in an ox­i­dized state – for ex­am­ple brown iron ore Fe₂O₃·3H₂O, red iron ore Fe₂O₃ (hematite), pyrite FeS₂, mag­net­ic iron ore Fe₃O₄.

Ob­tain­ing iron and its re­ac­tion with sim­ple sub­stances

Iron [Wikimedia]

Metal­lic iron is ob­tained in in­dus­try by re­duc­ing it from iron ox­ide with car­bon monox­ide CO:

  • Ob­tain­ing car­bon (IV) ox­ide from coal:

C + O₂ = CO₂;

  • Ob­tain­ing car­bon II ox­ide (re­duc­er for ob­tain­ing iron):

CO₂ + C = 2CO;

  • Re­duc­tion of iron from iron ox­ide:

Fe₂O₃ + 3CO = 2Fe + 3CO₂.

Iron can also be ob­tained di­rect­ly by re­duc­ing it with hy­dro­gen at a tem­per­a­ture of 1000 ᵒC (1832 ᵒF):

Fe₂O₃ + 3H₂ = 2Fe + 3H₂O.

Chem­i­cal­ly pure iron is ob­tained by elec­trol­y­sis of the so­lu­tion of its salt:

K(-): 1) 2H₂O + 2e = H₂ + 2OH⁻;

  1. Fe²⁺ + 2e = Fe(0).

A(+): 2H₂O - 4e = O₂ + 4H⁺.


Fe­S­O₄ + 2H₂O = Fe + H₂ + O₂ + H₂­SO₄.

With non-met­als, iron re­acts at high tem­per­a­tures:

  • 3Fe + 2O₂ = Fe₃O₄ (a mix­ture of iron (II) and (III) ox­ides form);

  • Fe + S = FeS;

  • 2Fe + 3Br₂ = 2FeBr₃.

Fe₃O₄ [Wikimedia]

Re­ac­tions of iron with com­plex sub­stances

At a tem­per­a­ture of 700 ᵒC (1292 ᵒF), iron re­acts with ben­zol with the for­ma­tion of iron car­bide:

18Fe + C₆H₆ = 6Fe₃C + 3H₂.

At room tem­per­a­ture in air and in the pres­ence of mois­ture, iron cor­rodes (cor­ro­sion is the spon­ta­neous dis­in­te­gra­tion of met­al un­der the im­pact of the en­vi­ron­ment):

4Fe + 3O₂ + 6H₂O = 4Fe(OH)₃ (re­ac­tion takes place rather slow­ly in nor­mal con­di­tions).

Corrosion [Wikimedia]

When iron is fused with an al­ka­li in the pres­ence of ni­trate, fer­rates form on the cation of the al­ka­li:

Fe + 3NaNO₃ + 2NaOH = Na₂FeO₄ + 3NaNO₂ + H₂O.

Click here for ex­cit­ing ex­per­i­ments with iron.

Iron en­ters into a dis­place­ment re­ac­tion read­i­ly (re­ac­tions in which atoms or groups of atoms of the same ini­tial sub­stance re­place atoms or groups of atoms of an­oth­er ini­tial sub­stance – for ex­am­ple ac­cord­ing to the scheme АВ + С = АС + В). With di­lut­ed acids, iron re­acts with the for­ma­tion of iron (II) salt and hy­dro­gen:

Fe + 2HCl = Fe­Cl₂ + H₂.

Con­cen­trat­ed ni­tric acid (and con­cen­trat­ed cold sul­fu­ric acid) pas­si­vates iron, and this re­ac­tion does not take place. With con­cen­trat­ed hot sul­fu­ric acid and di­lut­ed ni­tric acid, acid re­acts as fol­lows:

  • Fe + 6H₂­SO₄ = Fe₂(SO₄)₃ + 3SO₂ + 6H₂O (only with heat­ing);

  • Fe + 4H­NO₃ = Fe(NO₃)₃ + NO + 2H₂O.

With salts, iron may also en­ter into a dis­place­ment re­ac­tion. Be­tween cop­per (II) sul­fate and metal­lic iron, the fol­low­ing re­ac­tion takes place (an ex­am­ple of a typ­i­cal dis­place­ment re­ac­tion be­tween in­or­gan­ic sub­stances):

Fe + Cu­SO₄ = Fe­S­O₄ + Cu (iron dis­places cop­per in the salt so­lu­tion; the iron dis­solves, turn­ing into so­lu­tion, and metal­lic cop­per of a red­dish col­or is re­leased).

Copper sulfate [Wikimedia]

The re­ac­tion does not take place in this way with all salts – dis­place­ment is only pos­si­ble if the dis­plac­ing met­al is more re­ac­tive than the dis­placed one. As iron is to the left of cop­per in the re­ac­tiv­i­ty se­ries (is re­ac­tiv­i­ty in the se­ries de­creas­es from left to right), we may say that iron is a more ac­tive met­al than cop­per. This is why it dis­places cop­per from cop­per salt so­lu­tion.

We may ob­serve some vis­ual ef­fects when car­ry­ing out this re­ac­tion. Cu­SO₄ (“cop­per sul­fate” or cop­per (II) sul­fate) is a salt with a bluish col­or. When a sil­very iron bar is put in a cop­per sul­fate so­lu­tion, the so­lu­tion slow­ly starts to change col­or – the bright blue col­or grad­u­al­ly turns green (the salt Fe­S­O₄ which forms in re­place­ment has a green col­or). Metal­lic cop­per of a red­dish col­or also starts to form around the dis­solv­ing iron bar. As the cop­per in this re­ac­tion has a rather loose struc­ture, it may sep­a­rate from the iron bar and pre­cip­i­tate.

The re­ac­tion be­tween cop­per sul­fate and iron is ox­i­da­tion-re­duc­tion: iron is ox­i­dized and cop­per is re­duced:

Fe + Cu­SO₄ = Fe­S­O₄ + Cu;

There are two pro­cess­es:

  • Cu²⁺ + 2e = Cu⁰ (re­duc­tion process, Cu²⁺ is the ox­i­diz­er);

  • Fe⁰ – 2e = Fe²⁺ (ox­i­da­tion process, Fe⁰ is the re­duc­er).

Metal­lic cop­per is of­ten used for the man­u­fac­ture of pipes, wires and pow­er ca­bles. Cop­per al­loys are also of­ten used in prac­tice – for ex­am­ple, bronze (cop­per and tin), brass (cop­per and zinc) and du­ra­lu­min (cop­per and alu­minum).

Iron has found an ap­pli­ca­tion in prac­ti­cal­ly all branch­es of in­dus­try – iron salts are used as cat­a­lysts in or­gan­ic syn­the­sis (for ex­am­ple Fe­Cl₃), to pu­ri­fy­ing wa­ter and man­u­fac­tur­er iron al­loys – for ex­am­ple cast iron and var­i­ous steels (both types of al­loys con­tain iron and car­bon in dif­fer­ent ra­tios).