Iodine : Properties

Iodine

source : healthworry.com

Chemical properties:

1) Reaction with KI :

Iodine is soluble in KI due to formation of Potassium tri iodide complex(brown complex)

KI+I₂ —–> KI₃

2) Reaction with NaOH

a) With Cold and dilute NaOH : sodium iodide &sodium hypo iodite is formed.

2NaOH +I₂ ——> NaI +NaIO +H₂O

b) Hot and concentrated NaOH : 

sodium iodide & sodium iodate is formed.

6NaOH + 3I₂ ——> NaIO₃ + 5NaI + 3H₂O

3) Reaction with NH3 :

nitrogen tri-iodide ammonia is formed which is an  explosive. It explodes on heating or rubbing.

5NH₃ + 3I₂ ——> NI₃.NH_{3 [}nitrogen tri-iodide ammonia (explosive)] + 3NH4I

NI₃.NH₃  ——–> N₂ +I₂ +NH₄I

4) Oxidizing properties :

Iodine is weak oxidizing agent.

a) It oxidizes SO₂ into H₂SO₄:

I₂ +H₂O ——> 2HI + O

SO₂ + [O] +H₂O —–>H₂SO₄

Equation as a whole ,

I₂ + 2H₂O +SO₂ ——>H₂SO₄ +2HI

b) It oxidizes Na3AsO₃ to Na₃AsO₄:

I₂ +H₂O —–> 2HI + O

Na₃AsO₃  + O ——-> Na₃AsO₄

Equation as a whole ,

I₂ +H₂O + Na₃AsO₃ ——> 2HI + Na₃AsO₄

c) It oxidizes H₂S into S:

I₂ + H₂O ——> 2HI +O

H₂S +O ——> H₂O + S

Equation as a whole ,

I₂ +H₂S ——->2HI + S

d) It oxidizes hypo into  sodium tetrathionate.

2Na₂S₂O₃ (hypo) + I₂  ——> 2NaI +Na₂S₄O₆ (sodium tetrathionate)

e) It oxidizes SnCl₂ to SnCl₄ :

SnCl₂ +2HCl +I₂ ——-> SnCl₄ +2HI

5) Reaction with oxidizing agents:

Oxidizing agent oxidizes I₂ into Iodic acid.

a) Oxidation by Chlorine :

5Cl₂ +5H₂O ——> 10 HCl + 5 [O]

I₂ + 5 [O] +H₂O —–>2HIO₃

Equation as a whole,

5Cl₂ + 6 H₂O + I₂ ——–> 2HIO₃ +10HCl

b) Oxidation by Nitric acid :

[2HNO₃ —–> H₂O + 2NO₂ + [O]] x 5

10 HNO₃ ——->5 H₂O +10 NO₂ +5 [O]

I₂ +5 [O] +H₂O —–>2HIO₃

Equation as a whole,

10HNO₃ +I₂ ———> 2HIO₃ +10 NO₂ +4H₂O

c) Oxidation by Ozone :

5O₃ ——-> 5O₂ +5 [ O]

I₂ + 5[O] +H₂O ——>2HIO_3PO

Equation as a whole,

5O₃ + I₂ +H₂O —–>5O₂ + 2HIO₃

6) Basic properties of I₂ :

Iodine has weak tendency to form cation. Basic property  of I_{2  is due to formation of cation.}

ICl ——> I⁺ + Cl^–

IPO₄ ——>I³⁺ + PO4^3-

Test of Iodine :

1) It gives violet color with starch.

2)On heating the solution of C₂H₅OH, NaOH and I₂, yellow precipitate of iodoform are obtained.

Uses:

1. Colloidal solution of I₂ is used in the treatment of goitre(in this disease throat swells up).
2. In making iodoform test in lab.
3. In  preparing  tincture of iodine which is used as disinfectant. Tincture of iodine is prepared by dissolving iodine in rectified spirit.