Experiments with halogens and their compounds

 

  element required compound link to experiment
*

Cl

Al (foil)

NaCl

CuSO4·5H2O

HCl (10%)

Influence of combination of copper ions and chloride ions on reactivity of aluminium. A violent reaction only occurs, when both type of ions are present.

*

Cl, I, Br

Bi(NO3)3·xH2O

HNO3 (dilute)

HCl (dilute)

NaCl

KBr

KI

Bismuth complexes with halogens. Bismuth in its +3 oxidation state forms a black precipitate with iodide ions, and a deep orange complex is formed when excess iodide ion is present. Chloride and bromide also form complexes.

*

Br

KBr

K2Cr2O7 (or subst.)

Synthesis of potassium bromate. It is shown how potassium bromate can be made by means of electrolysis.

*

Br

NaBr

NaHSO4 (pH-minus)

Any soluble hexavalent chromium compound

Bromine from OTC compounds. Bromine is prepared from standard swimming pool chemicals. Only a very small amount of chromate or dichromate is needed, but this can be made easily as well (no need to isolate and purify this).

*

Br

Br2

Al (foil)

HCl (10%)

Na2SO3

Reaction between bromine and aluminium, spontaneous ignition of aluminium after some delay . Aluminium foil is added to some liquid bromine.

*

Br

Br2-water

NH3 (10%)

Formation of dense smoke from bromine and ammonia . Bromine vapor is poured into air, containing ammonia gas.

*

Br, Cl

Br2

Cl2

P (red)

Reaction between bromine/chlorine and phosphorus . Red phosphorus, when thrown in chlorine gas or bromine vapor, is ignited and continues burning in the gas.

* Br, I

NaBrO3

NH4NO3

HIO3

NH3 (12% or better)

Ammonium halates, unstable compounds . Ammonium bromate and ammonium iodate are prepared and it is demonstrated how easily and violently they decompose on slight heating. This is a nice and fairly spectacular experiment, but it should not be scaled up.
*

Br, P

P (red)

Br2

Synthesis and isolation of phosphorus tribromide . Phosphorus tribromide is prepared by means of careful addition of red phosphorus to bromine. By means of distillation the product is purified.

*

Cl

KCl

CsCl (optional)

K2Cr2O7 (optional)

HCl (dilute, optional)

Tutorial for making a miniature electrolysis cell for chlorate production. This is not really an experiment, it is a description of how one can setup a nice small electrolysis cell, suitable for making chlorates from chlorides. The good working of this cell is demonstrated for making potassium chlorate and cesium chlorate.

*

Cl

NaClO3

HCl (30%)

Ca(ClO)2·xH2O

Colored gases - chlorine and chlorine dioxide . Chlorine gas and chlorine dioxide are made. A comparison is made of the intensity of their colors.

*

Cl

NaClO2

HCl (30%)

Explosive properties of chlorine dioxide . The brightly colored chlorine dioxide gas is prepared and ignited. This results in a nice and quite spectacular decompositon reaction.

*

Cl

NaClO2

HCl (≥ 25%)

NH3 (5%)

Explosion of chlorine dioxide, initiated by presence of ammonia . Another experiment, which demonstrates the danger of chlorine dioxide. This experiment shows how chlorine dioxide can be brought to explosion, simply by adding a few drops of household ammonia.

 

Cl

NH3 (5%)

CuSO4·5H2O

organic swimming pool chlorine

Funny experiments with organic swimming pool chlorine. Several funny experiments with TCCA. Smoke production, formation of strange precipitates.

*

Cl

H2O2 (30%)

swimming pool tablets

Red chemiluminiscence with chlorine swimming pool chemicals. Hydrogen peroxide is added to sodium dichloro isocyanurate or to calcium hypochlorite. A nice red chemiliminiscent light is produced.

 

Cl, Br, I

Cl2

Br2

I2

Colored gases from halogens. Halogens are mixed, and the interhalogen compounds formed are shown in their vapor state.

*

Cl

Cl2

CaC2 ("carbide")

Violent 'combustion' of acetylene in chlorine gas, explosions without need of supplying heat . Acetylene gas is bubbled into chlorine and this leads to violent explosions.

*

Cl

any soluble Mn salt

any soluble Fe salt

bleach

Oxidizing power of bleach, bringing iron and manganese to highest oxidation state. Simple household bleach is capable of oxidizing iron to its +6 oxidation state and manganese to its +7 oxidation state.

* Cl, P

P (white)

NaOH

Cl2

bleach

HCl

Self-ignition of phosphine in chlorine gas . In this experiment some phosphine is prepared, and the gas is bubbled in an atmosphere of chlorine, resulting in self-ignition of the gas and contraction of gas volume. This demonstrates the high reactivity of chlorine.
*

Cl, P, Al

P (red)

Cl2

KNO3

Al (powder)

Miniature fireworks (bright flashes) in a test tube. A mix of aluminium powder, potassium nitrate and red phosphorus is thrown in chlorine gas. This results in a very bright white flash.

*

Cl, N

N2H4 (dilute, 20%)

HClO4 (dilute, 20%)

Violent decomposition of hydrazine perchlorate and fairy-like sparkles. A small quantity of hydrazine perchlorate is prepared and this compound is heated, leading to a peculiar fairy-like sparkling when heating is not too strong and violent deflagration on stronger heating.

*

Cl, Br, I, N

N2H4.2HCl

Ca(OCl)2

NaClO2

KClO3

KBrO3

KIO3

KIO4

Reactivity of different oxohalogenate ions. Several oxohalogenate compounds are added to a concentrated solution of hydrazine dihydrochloride. In many cases this leads to a reaction, some of them being very violent. A comparison is made of the reactivity of the different oxohalogenate ions at room temperature.

*

Cl, Br, I, Te

TeO2

Na2TeO3

HCl (30% by weight)

HBr (40% by weight)

H2SO4 (dilute)

KI

Na2SO3

Colorful properties of halogen complexes of tellurium in oxidation state +4. At very low pH, tellurium in oxidation state +4 forms remarkable compounds with the halide ions. The heavier the halogen, the more stable the complex and the more intense the color. All of these complexes, however, are very prone to hydrolysis in aqueous solution.

*

F

KMnO4

NaF

H2SO4 (concentrated)

Na2S2O5 (or Na2SO3)

A volatile compound of manganese and corrosion of glass . A volatile green compound of manganese(VII) is produced from potassium permanganate, sodium fluoride and conc. sulphuric acid.

 

I

KIO4

S

Pyrotechnic mix with purple gaseous combustion product. Potassium periodate, mixed with sulphur gives a mix, which burns without smoke, but produces a nice purple gas mix of iodine and sulphur dioxide.

 

I

NaIO4

many metal salts

Colorful precipitates with periodate ion. Many metal salts are mixed with a solution of sodium metaperiodate.

*

I

CHI3

Na2SO3

CH3COCH3

Decomposition of iodoform. Iodoform is heated and its decomposition products are shown.

*

I, Cl

KIO3

HCl (30%)

CH3COCH3

H2SO4

H2O2 (3%)

Na2SO3

Preparation of polyhalide salt of potassium. Potassium iodate is added to concentrated hydrochloric acid. Chlorine gas is formed, and needle-like crystals of potassium tetrachloroiodate(III) are formed as well. This is a remarkable polyhalide compound.

*

I, Cl

Rb2CO3

HIO3

HCl (30%)

A polyhalide compound of rubidium. Rubidium is known to form polyhalide compounds fairly easily, more so than the lighter alkali metals (see experiment above). In this experiment such a compound is prepared. During the preparation a beautiful crystalline precipitate is formed.

*

I, Cl

I2

Ca(ClO)2·xH2O

Mg

HCl (dilute)

Na2SO3

Example of interhalogen compounds . Chlorine gas is made, and this gas is lead over iodine. Iodine monochloride and iodine trichloride are formed. The monochloride is reacted with magnesium.

*

I

KIO3

KH(IO3)2

NaNO2

Reaction between molten nitrite and iodate, formation of beautiful wine red gas mixes.

*

I

KIO4

NH4SCN

Colored smoke -- purple and yellow. A mix of potassium periodate and ammonium thiocyanate is ignited. This gives purple smoke, which quickly turns yellow. Quite a remarkable experiment.

*

I

H5IO6

NH3

NaOH

Preparation and properties of ammonium periodate. A simple experiment, in which ammonium (meta)periodate is made. This compound explodes when it is heated.
*

I, Mg

Mg (powder)

I2

Na2SO3

Water-initiated violent reaction between magnesium and iodine. Magnesium and iodine are mixed, and a violent reaction is initiated by adding some water.

* I, N

H5IO6

N2H4

alternatives based on KIO4 and salts of hydrazine are possible

Violent reaction between hydrazine and periodate. In this experiment it is demonstrated that hydrazine and periodate react extremely violently and so much heat is produced that iodine escapes as vapor, even from aqueous solutions!
* I

KIO3

KOH

Cl2 (generated)

HNO3

Synthesis of potassium periodate. Potassium periodate is prepared by leading chlorine gas through a solution of potassium iodate and potassium hydroxide. Some acid is used to precipitate all of the periodate as the very sparingly metaperiodate.
* I

NaI

NaOH

Cl2 (generated)

 

Synthesis of sodium orthoperiodate. Sodium orthoperiodate is prepared by leading chlorine gas through a solution of sodium iodide and sodium hydroxide. The nice thing of this synthesis is that it allows one to make periodate without needing access to any special chemicals besides the easy to obtain sodium iodide.
* I, P

H5IO6

P (red)

Delayed self-ignition of mix of periodic acid and red phosphorus. Some red phosphorus and periodic acid are mixed. After a while, this mix suddenly self-ignites and a plume of fire and smoke is produced.
* I

I2

oleum (20% SO3)

 

Formation of cationic iodine species in oleum. Iodine is dissolved in oleum and the formation of a blue cationic species is demonstrated. Iodine is brought to oxidation state +½, which is very special for iodine.
*

I, Sn

Sn (preferably powder)

I2

CH2Cl2 or CS2

Preparation of tin(IV) iodide, a volatile covalent compound. Tin and iodine are made to react in a suitable solvent for iodine. Under these conditions the interesting compound tin(IV) iodide is formed, which can easily be isolated. Some properties of this compound are shown.

 

technical

NaBr

KBrO3

H2SO4 (concentrated)

Making bromine by distillation. Bromine is made in an acidic solution and this is distilled in order to obtain the pure element. It is dried with concentrated sulphuric acid.

 

 

   

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