Magnesium Nitrate – Structure, Formula, Properties, Reactions

Magnesium nitrate or magnesium dinitrate is an inorganic nitrate salt of magnesium. It is a white crystalline solid commonly used in pyrotechnics, that is hygroscopic in nature. It occurs naturally in mines and caverns. The following sections explore the formula, its molar mass, structure, properties, and uses.

The Formula for Magnesium Nitrate

The formula is Mg(NO₃)₂. The formula is derived using the crisscross method. The valency of magnesium is plus one, while that of nitrate is minus two. So, the formula is written as follows:

Magnesium Nitrate

Due to this chemical formula, It has the following names:

• Magnesium dinitrate (IUPAC name)
• Magniosan
• Nitromagnesite
• Magnesium nitrate hexahydrate

When this is exposed to air, it transforms into its hexahydrate form (Mg(NO₃)₂.6H₂O) as it is highly hygroscopic. However, magnesium nitrate is called nitromagnesite when it naturally occurs in the hexahydrate form.

Magnesium Nitrate Structure

This comprises magnesium and nitrate ions. The structure of magnesium is as follows:

Magnesium Nitrate

It contains a magnesium cation and two nitrate anions. An ionic bond occurs between magnesium and nitrate ions. Therefore, the compound is an ionic compound. Covalent bonds do exist in the compound nitrate anions as each nitrogen is covalently bonded to three oxygen atoms.

Lewis Dot Structure of Magnesium Nitrate

To draw the Lewis structure of Mg(NO₃)₂, you must understand the following concepts:

Ionic compounds are formed when metals react with nonmetals and give rise to a neatly packed crystalline solid. It is an ionic compound, and it is held together by ionic bonds. The compound has an overall neutral charge despite containing positively and negatively charged ions.

The nitrate anion in the compound contains covalent bonding. We can write its covalent Lewis structure as follows:

Nitrate ion

However, when you have to write the final Lewis structure of magnesium nitrate, you must follow the ionic compounds’ rule as write as follows:

Lewis Structure of Magnesium nitrate

Preparation of Magnesium Nitrate

Several methods have been employed to prepare in laboratories. Some of the most popular preparation methods are shared below:

From Magnesium Hydroxide and Nitric Acid

When one mole of magnesium hydroxide reacts with two moles of nitric acid, it gives one mole of magnesium nitrate. Nitric acid works as a dehydrating agent in the reaction. The balanced chemical reaction is as follows:

Mg(OH)₂+2 HNO₃→Mg(NO₃)₂+2 H₂O

From Magnesium Sulphate and Calcium Nitrate

It can be obtained when magnesium sulphate reacts with calcium nitrate. The balanced chemical equation for the reaction is as follows:

MgSO₄ + Ca(NO₃)₂ → Mg(NO₃)₂ + CaSO₄

From Magnesium Oxide and Nitric Acid

Just like the previous preparation method, when nitric acid reacts with magnesium oxide, it gives magnesium nitrate and water. The chemical reaction can be represented as follows:

MgO+ 2 HNO₃→Mg(NO₃)₂+H₂O

From Magnesium Carbonate and Nitric Acid

Another salt of magnesium, magnesium carbonate, can react with nitric acid to produce magnesium nitrate. The chemical equation for the reaction can be represented as follows:

MgCO₃+ 2 HNO₃→CO₂ + Mg(NO₃)₂+H₂O

From Magnesium and Dilute Nitric Acid

You can also use magnesium rather than its salts to produce magnesium nitrate. The chemical equation can be represented as follows:

Mg(s) + 2 HNO₃(aq) → Mg(NO₃)₂(aq) + H₂(g)

Properties of Magnesium Nitrate 

Magnesium nitrate molar mass	148.32 g/mol (anhydrous)
Density	2.3 g/cm3 (anhydrous)
Colour	White
State	Crystalline solid
Melting point	129 °C
Boiling point	330 °C
Solubility	Readily soluble in water and moderately in ammonia and ethanol
Nature	Hygroscopic
Crystal structure	Cubic

 

Magnesium Nitrate Molar Mass Calculation

You can easily calculate the magnesium nitrate molar mass using its chemical formula Mg(NO₃)_2.

The atomic weight of an atom of Mg is 24.

Nitrogen = 14

Oxygen = 16

The molecular mass of magnesium nitrate = Atomic weight of 1 Mg atom + Atomic weight of 2 Nitrogen atoms + Atomic weight of 6 oxygen atoms

Magnesium nitrate molecular mass = 1×24 + 2×14 + 6×16

Total mass = 24 + 28 +96

Total mass =148 g/mol

Therefore, the molecular mass of magnesium nitrate is 148 g/mol.

Chemical Reactions of Magnesium Nitrate 

Magnesium reacts with various hydroxides and carbonates to give desired products. Following are some of the important  reactions of magnesium nitrate:

Reaction with Hydroxides

It reacts with sodium hydroxide or other alkali metal hydroxide to give the following reaction:

Mg(NO₃)₂ + 2 NaOH → Mg(OH)₂ + 2 NaNO₃

Decomposition Reaction

This possesses a strong affinity for water. On heating, it decomposes into oxygen, magnesium oxide, and nitrogen oxide.

2 Mg(NO₃)₂ → 2 MgO + 4 NO₂ + O₂

Double Decomposition Reaction with Sodium Carbonate

It reacts with sodium carbonate to produce magnesium carbonate and sodium nitrate.

Mg(NO₃)₂ + Na₂CO₃ → MgCO₃ + 2 NaNO₃

Reaction with Water

It decomposes in water to give magnesium hydroxide, oxygen and ammonia. The following equation represents the reaction:

Mg(NO₃)₂ + 4 H₂O → Mg(OH)₂ + 2 NH₃ + 4 O₂

Thermal Decomposition On Heating

When magnesium nitrate is heated, it decomposes to give magnesium oxide. The reaction proceeds as follows:

2 Mg(NO₃)₂ → 2 MgO + 4 NO₂ + O₂

Reaction with Sulphuric Acid

Magnesium nitrate and sulphuric acid react to form nitric acid and magnesium sulphate. The chemical equation can be represented as follows:

H₂SO₄ +Mg(NO₃)₂→ MgSO₄ +2 HNO₃

Magnesium Nitrate Uses

This finds usage in various industries, including

• It is used as a desensitizer for lithographic plates.
• It is used as a dehydrating agent in the preparation of concentrated nitric acid and its purification.
• In the manufacturing of petrochemicals
• In manufacturing ammonium nitrate.
• As a viscosity adjuster in various industries
• In the manufacturing of agricultural products
• In the mining process
• It is used in making toner and colorant products.
• It can also be used as a binding agent.

Benefits of Using Magnesium Nitrate Fertilisers

These fertilizers provide plants with readily-available macro nutrient-magnesium. The primary benefits are as follows:

• It is essential for the healthy growth of plants.
• It also facilitates the uptake of magnesium by the plant.
• Lack of proper magnesium leads to necrosis in plants.
• It enriches plant nutrition and provides them with vitality.
• Since magnesium is the central atom in a chlorophyll molecule, its deficiency causes a shortage of chlorophyll and thus stunts plant growth. Conversely, a sufficient magnesium supply augments growth.

Health Hazards of Magnesium Nitrate

The seriousness of the impact of it depends on the exposure level. Less exposure to it can lead to the following conditions:

• Mild irritation in the mucous membranes
• Shortness of breath
• Coughing

Exposure to large quantities of this can lead to:

• Dizziness
• Vomiting
• Weakness
• Collapse
• Abdominal pain
• Bloody diarrhoea
• Convulsions

When this comes into contact with the skin, it causes:

• Redness
• Irritation
• Pain

In addition to its impact on humans, the compound can be dangerous if handled carelessly. It can result in violent combustion when in contact with oxidizable compounds. Also, one should be careful when heating this compound as it decomposes to emit toxic fumes of nitrogen oxides.

Conclusion

We now know that this is an inorganic chemical compound with the chemical formula Mg(NO₃)₂. It is hygroscopic in nature and usually occurs as a white crystalline solid at room temperature. It is an ionic compound.

You can easily obtain magnesium nitrate by reacting nitric acid with magnesium salts. It finds its application in textiles, mining, agriculture, and several other industries. However, one must be careful while handling magnesium nitrate as it serves as an irritant.

Frequently Asked Questions

1. What is the use of magnesium nitrate in nitric acid production?

A. It is used in the manufacture of concentrated nitric acid as it extracts water and provides concentrated acid vapors up to 90–95 percent.

2. Is magnesium nitrate acidic?

A. It is a crystalline solid, but it is highly hygroscopic. It has a pH of about 5-7 and is thus acidic in nature.

3. What metal will react with magnesium nitrate?

A. This does not react with zinc, lead, and copper because magnesium is higher than these in the reactivity series, i.e., it is more reactive than other metals. So, these metals cannot displace magnesium ions from the solution.

4. Is magnesium nitrate healthy?

A. No, It is harmful if ingested or inhaled. It can cause skin irritation as well as allergic reactions in the eyes and the respiratory tract. It irritates or burns the respiratory tract depending on the level of exposure. The person experiences coughing and shortness of breath.

5. How can you obtain magnesium nitrate crystals?

A. Although this is hygroscopic, you can obtain its crystals by drying it. You will have to heat it gently in a water bath. Cool the concentrated solution to obtain crystals. The heating process has to be slow; else, this would decompose and give magnesium oxide, nitrogen oxides, and oxygen.