Mercury is a naturally occurring chemical element that may be found in rocks all across the earth’s crust, including coal seams. It has the symbol Hg on the periodic table and an atomic number of 80. It may be found in both organic and inorganic substances. Mercury, also known as elemental or metallic mercury, is a gleaming silver-white metal that is liquid at ambient temperature and was once known as quicksilver. Older thermometers, fluorescent light bulbs, and certain electrical switches include it. Mercury may easily interact with chlorine, sulphur, and other elements, forming inorganic salts as a result of weathering.
Mercury (II) Chloride
Mercury (II) chloride formula is commonly known as Mercury dichloride formula or Mercuric chloride. It is synthesized chemically since it is not found naturally. It has a crystalline, solid white appearance and there is no odour to it. It dissolves easily in hot water, ethyl acetate, acetone, and ethanol, but not in cold water In carbon compounds such as benzene and pyridine, it dissolves somewhat.
Structure of Mercury (II) Chloride
The formula of Mercury (II) Chloride is made up of two chloride anions (Cl–) and one mercury (II) cation (Hg2+). Therefore, it has the molecular or chemical formula HgCl2. It has a molecular mass of 271.52 g/mol and has an orthogonal crystalline structure with linear coordination geometry and zero dipole moment.
Properties of Mercury (II) Chloride
- Pure Mercury (II) Chloride is colourless while solid and has no odour at all.
- The density of Mercury (II) Chloride is 5.43 g/cm3.
- The melting point of Mercury (II) Chloride is 276o C.
- The boiling point of Mercury (II) Chloride is 304o C.
- Mercury II Chloride is made up of linear triatomic molecules and has a sublime inclination.
- The standard enthalpy of formation of Mercury II Chloride is −230 kJ·mol−1.
- The standard molar entropy of Mercury II Chloride is 144 J·mol−1 K−1.
- The solubility of Mercury II Chloride in water is 3.6 g/100 mL at 0oC, 7.4 g/100 mL at 20oC and 48 g/100 mL at 100o C.
- It is acidic in nature with a pH of 3.2.
- The refractive index of Mercury (II) Chloride is 1.859.
- The magnetic susceptibility of Mercury (II) Chloride is -82.0 × 10-6 cm3/mol.
- It dissolves in chloride ions to give the tetrahedral coordination complex [HgCl4]2−.
- Each mercury atom is bound to two chloride ligands in its crystal form, with a Hg—Cl spacing of 2.38 Å and six additional chlorides are farther apart at 3.38 Å.
Uses of Mercury (II) Chloride
- Mercury II Chloride is an antibacterial agent. It’s capable of sterilizing bacterial cell walls.
- It’s used in anatomical specimen preservation, leather tanning, and as a reagent in analytical chemistry.
- It’s utilized in disinfectants and antiseptics, as well as an intensifier in photography.
- It’s utilized as a catalyst to convert acetylene to vinyl chloride, and its solution is used as a bulb and tuber dip.
- It’s utilized as an ant repellent and in dry battery casings.
- It’s employed in the production of amalgams with metals like aluminium.
- It’s utilized in the production of mercurography ink.
- In a umpolung reaction, it is utilized to remove dithiane groups linked to a carbonyl.
- It whitens and thickens the picture when added to a negative, increasing the opacity of the shadows and giving the impression of a positive image.
- It can be used to stabilise chemicals and analytical samples.
Sample Questions
Question 1. What is the process for the preparation of Mercury (II) Chloride?
Solution:
By adding hydrochloric acid to a heated concentrated solution of mercury(I) nitrate compounds, mercuric chloride is produced.
HgNO3 + 2 HCl → HgCl2 + H2O + NO2
Heating a combination of solid mercury(II) sulphate and sodium chloride produces volatile HgCl2, which may be separated by sublimation.
Question 2. How Mercury I Chloride is different from Mercury II Chloride?
Solution:
Calomel (Hg2Cl2) is a chemical compound that is also known as mercurous chloride or mercury(I) chloride. It is a soft, white halide mineral that is heavy, odorless, and tasteless. It is generated by the alternation of various mercury minerals, such as cinnabar or amalgams.
Question 3. How Mercury (II) chloride was used as a preserver?
Solution:
During the late nineteenth and early twentieth centuries, artefacts were dipped in or coated with a solution of Mercury (II) chloride to preserve anthropological and biological specimens. This was done to keep moths, mites, and mold from destroying the specimens. Objects in drawers were shielded by sprinkling crystalline mercuric chloride on top of them.
Question 4. Briefly explain the toxicity of Mercury (II) chloride.
Solution:
Mercuric chloride is extremely poisonous, both directly and cumulatively. This toxicity is caused not only by the presence of mercury, but also by the compound’s corrosive qualities, which may cause considerable interior damage such as stomach, mouth, and throat ulcers, as well as corrosive bowel damage.
Question 5. What are the various health hazards while using Mercury (II) chloride? Give any two safety measures to avoid them.
Solution:
Mercury (II) chloride is regarded as a highly hazardous substance. When ingested, any form of mercury is deadly. The likely fatal dose is 5-50 mg/kg. It is a hazardous mercury salt. It attacks the renal systems and gastrointestinal tract. When it comes into touch with the skin or eyes and causes extensive damage, it is deemed lethal.
Safety measures:
1. One should wear chemical masks and other protection equipment while using Mercury (II) chloride.
2. Close contact with the compound should be avoided, and it should be handled with care.