Question

write the equation for the decomposition of magnesium chloride hydrate

Answer 1

The decomposition reactions can be categorized into three types depending upon the nature of sample and strength of the bonds between its atoms or associated atoms/moieties:

1. Thermal decompotion reactions (by heating the samples)

2. Electrolytic decomposition reactions (by passage of electric current through the sample, electrolysis)

3. Photo decomposition reactions ( by exposure of sample to the sunlight)

The hydrate form of Magnesium chloride salt (MgCl₂.xH₂O) generally found in hexahydrate salts of magnesium chloride, i.e., (MgCl₂.6H₂O).

When hydrated salts of magnesium chloride are heated, the loosely attached water molecules get vaporized and magnesium chloride salt become anhydrous.

MgCl₂.xH₂O (s) ------heat------------> MgCl₂ (s) + xH₂O (g)

This is called thermal decompostion of magnesium chloride hydrates.

When solution of magnesium chloride hydrate (MgCl₂.xH₂O) are exposed to electric current, i.e., electrolysis of magnesium chloride, the water molecules (xH₂O) and chlorine gas (Cl₂) get off from the salts, and only Mg metal left which deposited on the electrodes.

MgCl₂.xH₂O (l) --------electric current-----> Mg (s) + Cl₂ (g) + xH₂O (l)

This reaction generally used for separation of purification of metals from their salts or mixtures.

Magnesium salts are not photo responsive, thus they do not decomposed when exposed to sunlight.

MgCl₂.xH₂O ------hv--------> No reaction