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Magnesium bromide is the combination of bromine and magnesium. The chemical formula of magnesium bromide is MgBr2. It is available in two different forms - anhydrous form and hexahydrate form. Magnesium bromide looks like a white hygroscopic crystal when in anhydrous form and colourless monoclinic crystal in hexahydrate form.
Key Terms: Magnesium Bromide, Crystals, Inhibitor, Catalyst, Periodic Table, Carnallite, Bischofite
Preparation of Magnesium Bromide
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Magnesium bromide can be prepared in different ways. The magnesium oxide (MgO) and hydrobromic acid (HBr) can be mixed to prepare magnesium bromide. The same can also be created from the reaction of magnesium carbonate (MgCO3 ) and hydrobromic acid (HBr). When the reactions are completed, evaporation takes place. After evaporation, a solid crystal is left which is mixable in water and alcohol. Magnesium bromide is naturally found in some minerals like carnallite or bischofite.
MgO + HBr\(\rightarrow\) MgBr2 + H2O
MgCO3 + HBr\(\rightarrow\) MgBr2 + CO2 + H2O
The below diagram depicts the chemical structure of magnesium bromide.
Structure of Magnesium Bromide
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Properties of Magnesium Bromide
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The important properties of magnesium bromide are given below:
- Chemical Formula:
- MgBr2 in anhydrous form, and
- MgBr2 .6H2O in hexahydrate form
- Molecular Weight:
- 184.113 g/mol (anhydrous form)
- 292.204 g/mol (hexahydrate form)
- Density:
- 3.72 g/cm3 (anhydrous form)
- 2.07 g/cm3 (hexahydrate form)
- Melting Point:
- 711°C (anhydrous form)
- 172.4°C (hexahydrate form)
- Boiling Point:
The boiling point of magnesium bromide is 1250°C.
Uses of Magnesium Bromide
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The different uses of magnesium bromide are given below:
- Magnesium bromide is the highest form of catalyst that is used in various reactions. It is generally used in the pharmaceutical department for solvent-free synthesis. It is used for making the calcium channel blockers in the medicines and is also used as an inhibitor. Sometimes, they are even used as tranquilizers. Since it is a combination of CH2Cl2, it is the highest form of catalyst used for the hydrogenation of alkenes.
- When magnesium bromide combines with other groups of chemicals, it does not act as a catalyst. In many practical cases, it has been used as a general group just to react with others.
- Magnesium bromide can also be used as a flame retardant. If 0.125 of magnesium bromide is added with a cotton-type item, it can behave like a flame retardant.
- The synthesis of magnesium can take place from magnesium bromide and lithium methyl. When the lithium gets exchanged with the magnesium and bromide is attached to the same, it becomes a complex compound. This compound is usable at room temperature.
- It is used as a catalyst in most medicines because magnesium bromide is helpful for the nervous cells of the human body. It can be a little sedative but highly effective if somebody faces any nerve problem. A small amount of magnesium bromide can be converted to react with the other compounds to turn it into a solid medicine.
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Reaction Between Magnesium and Bromide
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Magnesium is a metal present on the left-hand side of the periodic table. The metals on the left-hand side of the periodic table staircase tend to lose electrons. Therefore, magnesium has a charge of +2. On the other hand, bromine is found on the right-hand side of the periodic table charged with a -1 charge. When solid magnesium reacts with bromine, the two atom molecules of bromine combine and form a liquid that is reactive at room temperature. As already mentioned, the magnesium will lose electrons being plus charged and bromine being negatively-charged will gain such lost electrons. Magnesium will technically lose both its electrons and bromine whose charge is minus one will gain only one out of those two electrons. When a binary ionic compound is created after the combination of one metal and one non-metal, the charges get cancelled automatically to gain the chemical formula of an item.
Combination of Magnesium and Bromine
Technically, two bromines are required to cancel the two electrons of magnesium, however since there is no water to resolve the same and they are the solid ionic compounds, they will give rise to a single chemical with MgBr2. This whole process is called the synthesis reaction between magnesium and bromine.
In other words, magnesium is metal and bromine is non-metal and the combination of these two gives rise to an ionic compound named magnesium bromide. Always remember that pure magnesium will only have a proper reaction with pure bromine to give rise to magnesium bromide.
Read Also: Chemistry: Notes, Periodic Table, Chemical Reactions, Study Guides
Things to Remember
- The chemical formula of magnesium bromide is MgBr2.
- MgBr2 is found in two different forms - anhydrous and hexahydrate.
- MgBr2 is a strong catalyst and is also used as an inhibitor in some reactions.
- The reaction between magnesium (metal) and bromine (non-metal) is called the synthesis reaction.
- The ionic compound MgBr2 is formed when the electrons are lost by the positively-charged metal magnesium and absorbed by the negatively-charged non-metal bromine.
Sample Questions
Ques. How to write the formula of Magnesium Bromide? (5 marks)
Ans. The formula of magnesium bromide is written as MgBr2. You can use the periodic tables to write the formula of magnesium bromide. Follow the left side of the periodic table staircase for the metals where you'll find the magnesium and the right side of the periodic table staircase where you will find the bromine which is a nonmetal. As already mentioned, the metal and the non-metal give rise to a unique compound. Always remember to take charge of the compounds of both the metal and the non-metal. You must ensure that the charges of the metals and the nonmetals are balanced. When the plus two charges of magnesium react with minus one charge of bromine, the final charge of magnesium bromide does not balance out. To do the same, move the charges of magnesium to the bottom of bromide and the plus one charge of bromide to the bottom of magnesium. Remove the charges and you are left out with the final balanced formula of magnesium bromide (MgBr2). In the end, the net charge of magnesium bromide stands out to be 0 after the adjustment of the plus and the minus power.
Ques. Mention the solubility power of magnesium bromide in water in its two different forms. (3 marks)
Ans. In anhydrous form, magnesium bromide can mix in the water at 102g/100ml. In Hexahydrate form, magnesium bromide can mix in the water at 316g/100ml.
When working with ethanol and methanol, magnesium bromide can show up solubility of 6.9g/100ml and in methanol, the same can show the solubility of 21.8g/100ml
Ques. What are the uses of magnesium bromide in medicine? (3 marks)
Ans. The uses of MgBr2 in medicine are as follows:
- Magnesium bromide is a strong catalyst that can be used as a strong sedative in medicines.
- It is used to treat various nerve disorders and is used at all temperate levels in almost all medicines.
- Its solubility in water is 102g/100ml and is more efficient than any other compound.
- Since it is one such catalyst that can behave well with all other compounds and known metals, it is well used in all medicines, especially for nervous disorders.
Ques. State if magnesium bromide is safe? (5 marks)
Ans. It can only be used by the people who deal with the chemicals regularly. The combination of magnesium bromide with the other components can give rise to the solid particles of other compounds. But it can cause acute health hazards such as indigestion issues, irritation on the skin, and serious eye issues. If necessary precautions are not taken then it can also lead to respiratory issues and other serious exposures. It is stated that magnesium bromide if not used cautiously can target any organ and can affect the same toxically. Hence, to avoid such corrosion it is better to avoid raw magnesium bromide and must be dealt with optimum care.
Ques. State whether magnesium bromide is an electrolyte? (3 marks)
Ans. The electrolyte is something that dissolves in the water and produces ions to conduct electricity. Magnesium bromide is an ionic compound that helps in conducting electricity. It is soluble. When it is in the water, it will break in parts and will create ions. Hence, magnesium bromide is an electrolyte because the magnesium metal and the bromine non-metal dissolve in the water and have a high solubility power. The solution can generate electricity very well because the dissociation takes place nicely in the water.
Ques. Mention where you can get magnesium bromide. (2 marks)
Ans. By combining magnesium oxide and hydrobromic acid, one can form or crystallise into magnesium bromide. Once the synthesis process is completed the same gets evaporated and converted into solid. The solid is soluble in water as well as in alcohol. Furthermore, one can also get magnesium bromide in several minerals specially carnallite and bischofite.
Ques. Calculate the mass of the magnesium bromide if 720 ml of the aqueous solution is required with 0.0939 M. (5 marks)
Ans. M stands for Molarity.
If the 720ml is converted in L then it stands to be 0.72L.
Here, MgBr2 will be
0.0939mol/L × 0.72L
= 0.0676 mol
The mole of magnesium bromide is found in the absolute figure required. To find out the mass of magnesium bromide the mass is required to be added.
24.3g/mol Mg + 2(79.9g/mol Br)
=184g/mol MgBr2
Hence,
0.0676 mol MgBr2× 184g/mol MgBr2
= 12.4 g MgBr2.
Ques. When was bromine first found and where? (3 marks)
Ans. It was first found by a French chemist in 1826 in sea salt water residues. While checking the chlorine that can pass through the residues of the water, he came across the manganese bromide that was found in the water. When the manganese dioxide and sulphuric acid vaporizer, it got converted into a dark liquid. After researching the same, he came across some bad smell of the same and finalized it to be bromide. The mix was finally determined to be manganese bromide with high solubility in liquid and effective ion components.
Ques. Mention 4 uses of magnesium bromide. (3 marks)
Ans. The uses are as follows:
- It acts as a strong catalyst.
- It can be used as a sedative in medicines.
- It can be used as a tranquilizer.
- It can be used to determine the genesis of triglycerols.
Ques. State the properties of magnesium bromide. (5 marks)
Ans. The properties of MgBr2 are as follows:
| Property | Anhydrous Form | Hexahydrate Form |
|---|---|---|
| Chemical Property | MgBr2 | MgBr2 6H2O |
| Density | 3.72 g/cm3 | 2.07 g/cm3 |
| Molecule | 184.113 g/mol | 292.204 g/mol |
| Melting Point | 711°C | 172.4°C |
| Boiling Point | 1250°C | |
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