No, mercury does not dissolve in water.
In this article, we will talk about mercury and its properties, including, why it does not dissolve in water.
Does Mercury Dissolve In Water? (EXPLAINED)
Polarity exists when there is an uneven partial charge distribution between various atoms in a compound.
What is a polar molecule?
Well, it is a molecule that has opposite electric charges- positive and negative.
When we combine two substances with polar molecules, they can be attracted to each other.
Water is an excellent example of a polar molecule.
That is why water is considered a universal solvent- it dissolves a large number of elements.
Water Solubility: Structure of Water Molecule
As we know, not all elements or substances are water-soluble.
The structure of the water molecule is what determines if a substance dissolves in water or not.
Water consists of two elements, namely, hydrogen and oxygen.
Of the two, oxygen exhibits a stronger attraction to electrons.
As a result, bonding electrons (also known as shared electrons) spend more time in the neighborhood of oxygen than in the vicinity of hydrogen.
This is why oxygen demonstrates an excess negative charge, whereas hydrogen exhibits a more positive charge.
It is this unequal charge distribution that results in water being a polar molecule, which, in turn, results in its ability to dissolve substances.
Water has the ability to dissolve both ionic and non-ionic substances.
Now that we understand the structure of the water molecule, let’s try to understand why some substances do not dissolve in water.
As a general rule, substances that are non-polar and do not interact well with water molecules will not dissolve in water.
As we know, oil is another substance that does not dissolve in water.
Or, in other words, it is not water-soluble.
Properties of Mercury (Hg)
Mercury is a naturally-occurring chemical element, with the symbol Hg and atomic number 80.
Mercury exists in several forms, such as metallic mercury, inorganic mercury compounds, and methylmercury.
Unlike some other elements, pure mercury is quite stable.
At ordinary temperatures, it does not tarnish. Just like other metals (gold and lead), mercury does not dissolve in water.
Metals have a different molecular structure than that of water (H2O).
However, unlike other metals, mercury is a liquid at standard temperature and pressure.
Also, it is a relatively poor conductor of heat. It also differs from other metals in the sense that it is a mild electrical conductor.
While, in its pure form, mercury does not dissolve in water and other liquids, it does dissolve in fats and oils.
It is useful to note that mercury is the only common metal that is liquid at room temperature.
Interestingly, with a density of 13.53, mercury’s density is 13.6 times greater than that of water.
Mercury has a boiling point of 356.73 and a melting point of -38.534.
Understanding Water Solubility
Water (H2O) behaves differently with charged and polar substances than with non-polar elements.
This is due to the polarity of its own molecules.
As mentioned earlier, the hydrogen atoms carry a partial positive charge, while the oxygen atom carries a partial negative charge.
Due to this unequal charge distribution inside the H2O molecule, there is a high level of electronegativity of oxygen compared to that of hydrogen.
Thanks to its polarity, the water molecule can form electrostatic interactions with other polar molecules and ions.
What kind of substances dissolve in water?
Broadly speaking, ionic compounds and compounds with larger molecules will dissolve in water.
For example, table salt (sodium chloride) is an ionic compound that is water-soluble.
On the other hand, ammonia is a compound with larger molecules; yet, it is soluble in water.
Ammonia (NH3) has a unique molecular arrangement.
The three hydrogen atoms (H3) are asymmetrically arranged on the nitrogen atom (N).
This creates a positive charge on one side and a negative charge on the other.
When we add a polar substance (or solute) to water, water molecules are attracted to the metal.
They surround the charged molecules of the substance until their force of attraction exceeds the bond holding the substance together.
With the weakening of each solute molecule, the force of attraction of water molecules becomes stronger.
As a result, the solute dissolves into the water.
In the case of a solid solute, the process of dissolving may be gradual.
The dissolving begins with surface molecules.
A solution can also reach saturation if enough molecules are added to it.
A container holds a definite number of water molecules- it is not infinite.
When all water molecules have bonded to the solute atoms (or molecules), the solution is said to become saturated.
In other words, the solution will not dissolve the solute.
As mentioned earlier, some substances dissolve in water, and others do not.
Like most other metals, the molecular structure of mercury does not resemble that of water.
Due to this difference in molecular structure (and polarity), mercury does not dissolve in water in its pure form.
However, in other forms, such as mercuric chloride and methyl mercury, mercury is soluble in most organic solvents.
In fact, mercuric chloride is soluble in water as well.
In terms of solubility, we can classify elements into hydrophilic and hydrophobic.
Substances that easily dissolve in water are known as hydrophilic elements.
On the other hand, those that do not readily dissolve in water are called hydrophobic elements.
The latter (hydrophobic) generally contains large, non-polar molecules, such as fats and oils.
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