Identify-The Structure of SnCl₂

JEE Crash Course 2022

What is Tin (II) chloride – SnCl₂?

In solid form, SnCl2 is a crystalline mass whose chemical name is Tin (II) chloride. Some other names of Tin (II) chloride are Tin dichloride, or Dichlorotin, or Tin Proto Chloride, or Stannous chloride. It has a lone pair of electrons where the molecule in the gaseous phase is bent.

It appears as a white crystalline solid which is odourless. It is toxic when swallowed and irritates eyes and skin when it comes to contact. It is widely used in the manufacturing of pharmaceuticals, as a tanning agent, and in the production of dyes.

Properties of Tin (II) chloride – SnCl2

Chemical Formula- SnCl2

Chemical name is Tin (II) chloride

The molecular weight of SnCl2

189.60 g/mol (anhydrous)

The density of Tin (II) chloride

3.95 g/cm3 (anhydrous)

The boiling point of Tin (II) chloride

623 °C

The melting point of Tin (II) chloride

247 °C

The Structure of Tin (II) Chloride SnCl2

The structure of SnCl2 is a trigonal pyramidal shape or we can say that V shape due to the presence of a lone pair of electrons based on VSEPR theory.

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The exact mass and the mono-isotopic mass of Tin dichloride is 189.84 g/mol. The number of hydrogen bond acceptors and the number of hydrogen bond donors equals to zero. This compound is canonicalized and has one covalently bonded unit only.

VSEPR Theory

In chemistry, VSEPR Theory is used to predict the shape of the molecules from the electron pairs that surround the central atoms of the molecule. This theory is based on the assumption that the molecule will take a shape such that electronic repulsion in the valence shell of that atom is minimized.

The VSEPR theory is based on the principle that there is a repulsion between the pairs of valence electrons in all atoms. The arrangement of atoms will always be in such a manner in which this electron pair repulsion is minimalized. With the help of this arrangement of the atom, we determine the geometry of the resulting molecule.

Trigonal Planar Shape of Molecule

  • In the Trigonal Planar Shape of the molecule, we find three molecules attached to a central atom.

  • Atoms are arranged in such a manner that repulsion between the electrons can be minimized towards the corners of an equilateral triangle.

For Example: SnCl2

How VSEPR Theory Predicts the Shapes of Molecules

The strength of the repulsion between a lone pair and a bond pair of electrons lies in between the repulsion between two lone pairs and between two bond pairs. 

  1. Total number of electron pairs around the central atom = 1/2  x (number of valence electrons of central atom + number of atoms linked to central atom by single bonds)

  • For negative ions, add the number of electrons equal to the units of negative charge on the ions to the valence electrons of the central atom.

  • For positive ions, subtract the number of electrons equal to the units of positive charge on the ion from the valence electrons of the central atom.

  1. The number of Bond pairs = Total number of atoms linked to the central atom by single bonds.

  2. So, the number of lone pairs in a molecule = Total number of electron – Number of shared pair

  3. The electron pairs around the central atom repel each other and move so far apart from each other that there are no greater repulsions between them. As a result of this, the molecule has minimum energy and maximum stability.

Estimating the Shapes of the Molecules

The following steps must be followed in order to decide the shape of a molecule.

  • The least electronegative atom must be selected as the central atom (since this atom has the highest ability to share its electrons with the other atoms belonging to the molecule).

  • The total number of electrons belonging to the outermost shell of the central atom must be counted.

  • The total number of electrons belonging to other atoms and used in bonds with the central atom must be counted.

  • To obtain the valence shell electron pair number or the VSEP number, we must add these two values.

Uses of SnCl2

  • Tin (II) chloride is used as a strong reducing agent.

  • Used in the manufacturing of pharmaceutical products.

  • Used in removing ink stains.

  • Used as an additive in lubricating oils.

  • Used as a catalyst.

  • Used to manufacture colour pigments.

  • Used in tin-plating of steel.

  • Used in radionuclide angiography.

  • Used as a mordant in textile dyeing.

  • Used to produce plastic polylactic acid.

Production of Tin (II) Chloride

When we treat dry hydrogen chloride gas with tin metal we obtain Anhydrous Dichlorotin. The dihydrate is prepaid by using hydrochloric acid (HCl):

Sn(s) + 2HCL(aq) ⟶ SnCl2 + H2(g)

The dihydrate is dehydrated to anhydrous by treating with acetic anhydride.

Health Hazards

There are harmful effects of SnCl2 on our health. Tin Proto Chloride is toxic and corrosive in nature but it is a non-combustible compound. Inhaling, swallowing, or skin contact with this compound can cause severe injuries or lead to death. In its molten form, it may result in severe burns on the skin and in the eyes. When heated, it liberates corrosive, irritating, and toxic gases.

Did You Know?

  • Tin (II) chloride is made when tin dissolves in hydrochloric acid.

  • SnCl2 is a better reducing agent than HgCl2

  • Nowadays many toothpaste brands have been adding SnCl2 as protection against enamel erosion to their formula.

  • SnCl2 also reduces quinones to hydroquinones.

  • SnCl2 molecule is angular as Sn is sp2 hybridized with a bond angle of 120o

FAQs (Frequently Asked Questions)

1. Does Tin dissolve in hydrochloric acid?

Ans. Metallic tin is brittle and abrasive. It dissolves gradually in dilute non-oxidizing acids, or in hot concentrated HCl  more readily. The meta stannic acid, H2SnO3, is formed when it interacts with HNO3 , which is an insoluble white material in alkali or acids.

2. Is SnCl4 aqueous?

Ans. Anhydrous Stannic chloride is a colorless fuming liquid with a pungent scent. With heat evolution it is soluble in cold water and decomposed by hot water to form hydrochloric acid. Tin Chloride (SnCl4) is a food-borne antioxidant.