Iron and chlorine as simple substances, and their interaction

In this ar­ti­cle, we will ex­am­ine iron and chlo­rine, and also the re­ac­tion of these two sub­stances.

Iron is one of the most abun­dant met­als in the Earth’s crust. This met­al has been known from an­cient times, and it would prob­a­bly be im­pos­si­ble to imag­ine hu­man life to­day with­out iron, which is used in large-scale pro­duc­tion and takes part in the hu­mans' and an­i­mals' bi­o­log­i­cal pro­cess­es.

Phys­i­cal prop­er­ties of iron

In pure form, the met­al is quite mal­leable, but cer­tain ad­di­tives can in­crease its brit­tle­ness or strength. Iron has a dark sil­ver col­or and ac­tive­ly dis­plays mag­net­ic prop­er­ties. Iron is a high-melt­ing met­al and dis­plays medi­um chem­i­cal ac­tiv­i­ty.

The met­al melts at the rather high tem­per­a­ture of 1539 °C and boils at 2862 °C.

Chem­i­cal prop­er­ties of iron

Metal­lic iron re­acts with wa­ter va­por only at a high tem­per­a­ture of up to 800 °C. Mixed iron ox­ide Fe₃O₄ and hy­dro­gen form. Iron also re­acts quite well with di­lut­ed ni­tric acid. It can also re­act with halo­gens when heat­ed, with air, with non-met­als etc.

What is chlo­rine?

Chlo­rine is a chem­i­cal­ly ac­tive sub­stance which un­der stan­dard con­di­tions is in a gaseous state, and this gas has an acrid smell and a yel­low­ish tinge. If iron is one of the most abun­dant met­als in the Earth’s crust, chlo­rine is the most abun­dant halo­gen. It also takes part in im­por­tant bi­o­log­i­cal pro­cess­es of all liv­ing crea­tures on Earth.

Chlo­rine is heav­ier than air and is wide­ly used in in­dus­try. In pure form, the 17th el­e­ment is tox­ic to hu­mans and caus­es suf­fo­ca­tion if it en­ters the lungs.

This suf­fo­cat­ing gas boils at a tem­per­a­ture of -34 °C and melts at a tem­per­a­ture of -101.5 °C.

Chlo­rine re­acts read­i­ly with non-met­als, form­ing chlo­rides. For ex­am­ple, the equa­tion of the for­ma­tion of phos­pho­rus chlo­ride is:

3Cl₂ + 2P → 2P­Cl₃

Chlo­rine re­acts with hy­dro­gen. Hy­dro­gen chlo­ride forms, which when di­lut­ed with wa­ter gives strong hy­drochlo­ric acid:

H₂ + Cl₂ → 2HCl

Chlo­rine has quite a spec­tac­u­lar re­ac­tion with an­ti­mo­ny pow­der. An­tin­o­my is a semi-met­al, or a met­al­loid. If heat­ed an­ti­mo­ny pow­der is added to chlo­rine gas with a spe­cial spoon, flames, sparks and a thick white smoke of an­tin­o­my chlo­ride will form at the bot­tom of the flask:

2Sb + 3Cl₂ = 2S­b­Cl₃

This sub­stance can en­ter into a re­ac­tion with al­most all met­als.

Let us ex­am­ine the re­ac­tion with one of the ac­tive al­ka­lis - potas­si­um. The heat­ed met­al burns in chlo­rine, and potas­si­um chlo­ride forms:

2K + Cl₂ = 2KCl

With low-ac­tive met­als, for ex­am­ple cop­per, chlo­rine also re­acts, form­ing cop­per(II) chlo­ride.

Cu + Cl₂ → Cu­Cl₂

But the re­ac­tion with iron is es­pe­cial­ly vi­o­lent – let’s ex­am­ine it. This ex­per­i­ment can only be car­ried out in a lab­o­ra­to­ry.

For the ex­per­i­ment we will need:

• iron rod;
• gas burn­er;
• chlo­rine.

As we said, chlo­rine is heav­ier than air, so for the ex­per­i­ment, it can be stored in an open flask. The re­ac­tion takes place with an iron heat­ed up to 200 de­grees, so the rod should be heat­ed with the burn­er. Then low­er the rod into the green­ish gas, and ob­serve an im­me­di­ate vi­o­lent re­ac­tion: the chlo­rine ox­i­dizes the iron to a triva­lent state. The re­ac­tion is ac­com­pa­nied by the re­lease of tox­ic brown fumes, and crys­tals of iron chlo­ride start to form in the flask:

2Fe + 3Cl₂ = 2Fe­Cl₃

Warn­ing! Be­fore con­duct­ing the ex­per­i­ment, get to know with safe­ty rules, wear pro­tec­tive gloves and a mask. Do not breathe in the chlo­rine and the brown fumes that form! Iron chlo­ride has the for­mu­la Fe­Cl₃ and con­sists of small yel­low­ish crys­tals, which dis­solve well in wa­ter. Iron chlo­ride is used for in­dus­tri­al pur­pos­es, for ex­am­ple for wa­ter pu­rifi­ca­tion. The sub­stance is tox­ic.