Chlorine Gas (Cl2) - Structure, Molecular Mass, Properties and Uses

Edited By Shivani Poonia | Updated on Jul 02, 2025 07:24 PM IST

Imagine walking into a public swimming pool and feeling confident that the water does not contain any bacteria or viruses that will prove detrimental to your health. Alternatively, consider the convenience of turning on a tap and finding that safe potable water is already available without any second thoughts formally taken. Such everyday comforts are realized through the ubiquitous use of chlorine gas in the water treatment and sanitation process.

This Story also Contains

Physical Properties of Group 13 – 1
Group 13 - 2 Physical Properties
Hydrogen Chloride
Hydrogen bromide and Hydrogen iodide
Relevance and Applications
Some Solved Examples
Summary

Chlorine Gas (Cl2) - Structure, Molecular Mass, Properties and Uses

Discovered in 1774 by Swedish chemist Carl Wilhelm Scheele, chlorine gas has over the years evolved to become not only one of the highly used elements but also one of the essential chemicals in many industries today, from health to industrial manufacturing. It's from this gas that among the world's most powerful disinfecting actions have been developed, revolutionizing thus how hygiene and sanitation are approached today. It efficiently kills a wide spectrum of pathogens and is really of great importance to the concern for safety regarding the hygiene of drinking water and swimming pools.

Physical Properties of Group 13 – 1

Chlorine gas, though of the halogen group in the periodic table, falls under Group 17 and not Group 13. But its physical properties are of importance. Chlorine is a greenish-yellow gas with a pungent, suffocating odour. It is denser than air; the density comes to about 3.21 grams per liter at room temperature. The melting and boiling points of chlorine are -101.5°C and -34.04°C respectively, making it a gas under standard conditions: well soluble in water to give a pale-yellow solution, soluble in organic solvents like carbon tetrachloride. Such physical properties make chlorine gas very reactive and easily dispersible, the boon and bane in its applications.

Preparation

It can be prepared by anyone of the following methods:

By heating manganese dioxide with concentrated hydrochloric acid.
$
\mathrm{MnO}_2+4 \mathrm{HCl} \rightarrow \mathrm{MnCl}_2+\mathrm{Cl}_2+2 \mathrm{H}_2 \mathrm{O}
$
However, a mixture of common salt and concentrated $\mathrm{H}_2 \mathrm{SO}_4$ is used in place of HCl .
$
4 \mathrm{NaCl}+\mathrm{MnO}_2+4 \mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{MnCl}_2+4 \mathrm{NaHSO}_4+2 \mathrm{H}_2 \mathrm{O}+\mathrm{Cl}_2
$
By the action of HCl on potassium permanganate.
$
2 \mathrm{KMnO}_4+16 \mathrm{HCl} \rightarrow 2 \mathrm{KCl}+2 \mathrm{MnCl}_2+8 \mathrm{H}_2 \mathrm{O}+5 \mathrm{Cl}_2
$

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Properties

It is a greenish-yellow gas with a pungent and suffocating odour. It is about 2-5 times heavier than air. It can be liquefied easily into greenish-yellow liquid which boils at 239 K. It is soluble in water.
Chlorine reacts with a number of metals and non-metals to form chlorides.

$\begin{aligned} & 2 \mathrm{Al}+3 \mathrm{Cl}_2 \rightarrow 2 \mathrm{AlCl}_3 \\ & \mathrm{P}_4+6 \mathrm{Cl}_2 \rightarrow 4 \mathrm{PCl}_3\end{aligned}$

It has great affinity for hydrogen. It reacts with compounds containing hydrogen to form HCl.

$\begin{aligned} & \mathrm{H}_2+\mathrm{Cl}_2 \rightarrow 2 \mathrm{HCl} \\ & \mathrm{C}_{10} \mathrm{H}_{16}+8 \mathrm{Cl}_2 \rightarrow 16 \mathrm{HCl}+10 \mathrm{C}\end{aligned}$

With cold and dilute alkalies chlorine produces a mixture of chloride and hypochlorite but with hot and concentrated alkalies it gives chloride and chlorate.

$\begin{aligned} & 2 \mathrm{NaOH}+\mathrm{Cl}_2 \rightarrow \mathrm{NaCl}+\mathrm{NaOCl}+\mathrm{H}_2 \mathrm{O} \\ & 6 \mathrm{NaOH}+3 \mathrm{Cl}_2 \rightarrow 5 \mathrm{NaCl}+\mathrm{NaClO}_3+3 \mathrm{H}_2 \mathrm{O}\end{aligned}$

Chlorine reacts with hydrocarbons and gives substitution products with saturated hydrocarbons and addition products with unsaturated hydrocarbons.

$\stackrel{\text { CH }}{\mathrm{CH}_4}+\mathrm{Cl}_2 \xrightarrow{\mathrm{UV}} \mathrm{CH}_3 \mathrm{Cl}+\mathrm{HCl}^{-}$

Chlorine water on standing loses its yellow colour due to the formation of HCl and HOCl. Hypochlorous acid (HOCl) so formed, gives nascent oxygen which is responsible for oxidizing and bleaching properties of chlorine.

Chlorine is a powerful bleaching agent; bleaching action is due to oxidation. It bleaches vegetable or organic matter in the presence of moisture. The bleaching effect of chlorine is permanent.

$\mathrm{Cl}_2+\mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{HCl}+\mathrm{O}$

Uses

It is used for bleaching wood pulp, cotton, and textiles
It is used in the extraction of gold and platinum
It is used in the manufacture of dyes, drugs, and organic compounds such as CCl₄, CHCl₃, DDT, refrigerants, etc.
It is used in sterilizing drinking water
It is used in the preparation of poisonous gases such as phosgene (COCl₂), tear gas(CCl₃NO₂), and mustard gas (ClCH₂CH₂SCH₂CH₂Cl).

Group 13 - 2 Physical Properties

The chlorine gas is made up of a diatomic molecule with the chemical formula Cl₂. The gas is highly electronegative in nature and hence acts as an excellent oxidizing agent because of its electronegative nature and electron affinity. It disproportionates in water to form hydrochloric acid, HCl, and hypochlorous acid, HClO—this reaction forms the basis for its disinfectant properties. Chlorine gas is also known to react with a wide range of substances, including metals, nonmetals, and organic compounds. Its reactivity and toxicity mean it has to be handled and stored safely, mostly pressurized in cylinders or as a liquid under pressure. Knowing this kind of information about properties is quite important in using chlorine gas both safely and effectively in various settings.

Hydrogen Chloride

Preparation

In the laboratory, it is prepared by heating sodium chloride with concentrated sulphuric acid.

$\begin{aligned} & \mathrm{NaCl}+\mathrm{H}_2 \mathrm{SO}_4 \xrightarrow{420 \mathrm{~K}} \mathrm{NaHSO}_4+\mathrm{HCl} \\ & \mathrm{NaHSO}_4+\mathrm{NaCl} \xrightarrow{823 \mathrm{~K}} \mathrm{Na}_2 \mathrm{SO}_4+\mathrm{HCl}\end{aligned}$

HCl gas can be dried by passing through concentrated sulphuric acid.

Properties

It is a colourless and pungent-smelling gas. It is easily liquefied to a colourless liquid (b.p.189 K) and freezes to a white crystalline solid(f.p. 159 K). It is extremely soluble in water and ionizes as follows:

$\mathrm{HCl}(\mathrm{g})+\mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{H}_3 \mathrm{O}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})$

Its aqueous solution is called hydrochloric acid. The high value of the dissociation constant (K_a) indicates that it is a strong acid in water. It reacts with NH₃ and gives white fumes of NH₄Cl.

$\mathrm{NH}_3+\mathrm{HCl} \rightarrow \mathrm{NH}_4 \mathrm{Cl}$

When three parts of concentrated HCl and one part of concentrated HNO₃ are mixed, aqua regia is formed which is used for dissolving noble metals, e.g., gold, and platinum.

Uses

It is used in the manufacture of chlorine, NH₄Cl, and glucose (from corn starch).
It is used for extracting glue from bones and purifying bone black.
It is used in medicine and as a laboratory reagent.

Hydrogen bromide and Hydrogen iodide

$\begin{aligned} & \mathrm{NaI}+\mathrm{H}_3 \mathrm{PO}_4 \rightarrow \mathrm{HI}+\mathrm{NaH}_2 \mathrm{PO}_4 \\ & \mathrm{NaBr}+\mathrm{H}_3 \mathrm{PO}_4 \rightarrow \mathrm{HBr}+\mathrm{NaH}_2 \mathrm{PO}_4\end{aligned}$

In the laboratory, HBr and HI are prepared in the following ways:

$\begin{aligned} & 2 \mathrm{P}(\text { red })+3 \mathrm{Br}_2 \rightarrow 2 \mathrm{PBr}_3 \xrightarrow{+6 \mathrm{H}_2 \mathrm{O}} 6 \mathrm{HBr}+2 \mathrm{H}_3 \mathrm{PO}_3 \\ & 2 \mathrm{P}(\text { red })+3 \mathrm{I}_2 \rightarrow 2 \mathrm{PI}_3 \xrightarrow{+6 \mathrm{H}_2 \mathrm{O}} 6 \mathrm{HI}+2 \mathrm{H}_3 \mathrm{PO}_3\end{aligned}$

Relevance and Applications

There are a number of industries and public health initiatives where chlorine gas is put into practice every day. Mainly applied in purifying water to kill bacteria, viruses, and many other types of pathogens, it works to ensure safe drinking water across the globe. In the manufacture of paper, chlorine is broadly used in textile production and plastics like polyvinyl chloride or PVC. This, however, is a fairly versatile plastic used in construction and packaging. Chlorine compounds in the medical field are antiseptics and disinfectants; hence, these will prove useful in avoiding infections. It is further used by many pharmaceutical firms for making a large number of remedial pharmaceutical products, some of which are life-saving drugs. However, since chlorine itself is a toxic and corrosive gas, causing respiratory troubles and skin irritations, it needs handling with due care. Proper measures of safety and regulations related to handling such a dangerous gas will keep their risks under check.

Some Solved Examples

Example 1
Question:

When O₃reacts with HCl, it converts HCl into

1)HClO

2) (correct)Cl₂

3)Cl^-

4)ClO₃^-

Solution:

As we have learned,

Halides generally react with good oxidizing agents and are converted to the respective halogen. Thus, ozone oxidizes HCl to form Chlorine gas.

$2 \mathrm{HCl}+\mathrm{O}_3 \rightarrow \mathrm{Cl}_2+\mathrm{H}_2 \mathrm{O}+\mathrm{O}_2$

Hence, the answer is the option (2).

Example 2
Question:

Pure Cl₂ is obtained by heating

1)AgCl

2)MgCl₂

3) (correct)AuCl₃

4)FeCl₃

Solution:

As we have learnt,

Pure Chlorine can be obtained by heating the chlorides of metals having low reactivity like Au or Pt. The reactions are given as,

$2 \mathrm{AuCl}_3 \xrightarrow{\Delta} 3 \mathrm{Cl}_2+2 \mathrm{Au}$

$\mathrm{PtCl}_4 \xrightarrow{\Delta} 2 \mathrm{Cl}_2+\mathrm{Pt}$

Hence, the answer is the option (3).

Example 3
Question:

When sodium thiosulphate reacts with Cl₂ it forms

1)NaOH

2) (correct)NaHSO₄

3)Na₂S₂O₃

4)Na₄S₄O₆

Solution:

As we have learnt,

Reaction of Chlorine with Sodium thiosulfate,

_{$\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3+4 \mathrm{Cl}_2+5 \mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{NaHSO}_4+8 \mathrm{HCl}$}

Hence, the answer is the option (2).

Summary

Among the myriad important chemicals that find versatile applications in almost all spheres of human life is water purification, through industrial manufacturing, to healthcare-stands chlorine gas. The physical properties, such as high reactivity and good solubility, make chlorine gas a good disinfectant and a valuable industrial reagent. However, its very toxic nature does guarantee that extra care is exercised during its handling and stringent safety measures are ensured.

Frequently Asked Questions (FAQs)

1. 1. What are the main uses of chlorine gas?

Chlorine gas is mostly used in disinfecting drinking water and swimming pool water. It kills bacteria and other average microorganisms to obtain safe and clean water. Other than this, chlorine gas finds its application in the manufacture of paper, textiles, and plastics like polyvinyl chloride popularly known as PVC. The compounds of chlorine are also used as antiseptics and disinfectants in hospitals in order to prevent infections.

2. 2. How is chlorine gas obtained?

Chlorine gas is prepared by the usual electrolysis of sodium chloride solution, common table salt. An electric current is introduced in this industrial process called the chloralkali process into brine or a concentrated solution of sodium chloride. Chlorine gas, hydrogen gas, and sodium hydroxide are formed through this electrolysis. The chlorine gas formed is collected and purified for industrial and commercial uses.

3. 3. What are the safety precautions when handling chlorine gas?

The most critical safety measures adopted to prevent exposure and other related hazards of chlorine gas in its handling are protective equipment such as gloves and safety goggles, gas masks, good ventilation in an area where chlorine is either used or stored, storing cylinders in a safe and upright position away from the direct rays of the sun and heat sources.
- Follow established processes for responding to leaks and spills of chlorine gas with access to first aid apparatus including emergency showers and eyewash
- Provision for regular training of all personnel handling and storing chlorine gas on good safety techniques in their handling and storage.

4. 4. Can chlorine gas be harmful to humans?

Yes, chlorine gas is toxic and thus poses a potential threat to human life. Chlorine gas, when inhaled into the lungs, can cause acute respiratory effects ranging from cough, chest tightness, and shortness of breath. Much higher concentrations may cause fatal pulmonary edema. Exposure through contact with chlorine gas causes serious skin and eye irritation. If exposed, immediate medical attention should be sought with decontamination procedures followed to minimize health risk.

5. 5. What is the product of the reaction of chlorine gas in water?

Upon dissolving in water, chlorine gas, Cl₂ reacts to become a mixture of hypochlorous acid, HClO, and hydrochloric acid, HCl. Such a reaction can be front-lined by the following chemical equation:
$[ \text{Cl}_2 + \text{H}_2\text{O} \rightarrow \text{HClO} + \text{HCl} ]$
Hypochlorous acid is a strong disinfectant that accounts for the majority of the sanitizing properties of chlorine. It kills bacteria, viruses, and other pathogens efficiently in water and forms an important constituent for the treatment of this very resource.

6. What is the significance of chlorine's atomic radius in the formation and properties of Cl2?

Chlorine's atomic radius (79 pm) is smaller than other halogens except fluorine. This small size contributes to the strength of the Cl-Cl bond and affects the molecule's reactivity. The compact size allows for effective orbital overlap in bonding and influences properties such as bond length, bond strength, and the molecule's overall size.

7. What is the relationship between the electronic configuration of chlorine and the magnetic properties of Cl2?

Cl2 is diamagnetic, meaning it is slightly repelled by magnetic fields. This is due to the pairing of all electrons in the molecule, including the electron involved in the covalent bond. The diamagnetic property arises from the electronic configuration of chlorine atoms and how they combine to form the Cl2 molecule, with no unpaired electrons in the ground state.

8. What is the significance of chlorine's electronegativity in understanding the polarity of Cl2?

Chlorine's high electronegativity (3.16 on the Pauling scale) is crucial in understanding why Cl2 is non-polar despite chlorine's tendency to attract electrons. In Cl2, both atoms are equally electronegative, resulting in an equal sharing of electrons and no net dipole moment. This contrasts with compounds like HCl, where the difference in electronegativity leads to a polar molecule.

9. How does the molecular orbital theory explain the bonding in Cl2?

In molecular orbital theory, the bonding in Cl2 is described by the overlap of atomic orbitals to form molecular orbitals. The single covalent bond results from the overlap of one 3p orbital from each chlorine atom, forming a bonding σ molecular orbital. The theory also accounts for the presence of non-bonding orbitals containing lone pairs.

10. What is the significance of chlorine's electron affinity in understanding its chemical behavior?

Chlorine has a high electron affinity (349 kJ/mol), which means it readily accepts an electron to form a chloride ion. This property contributes to chlorine's strong oxidizing ability and its tendency to form ionic compounds. It also explains why chlorine often exists as Cl- in many compounds rather than maintaining its Cl2 form.

11. How does the ionization energy of chlorine atoms relate to the properties of Cl2?

The high ionization energy of chlorine (1251 kJ/mol for the first ionization) contributes to its tendency to form covalent bonds rather than ionic bonds in its elemental state. This property influences the formation of Cl2 molecules and affects its reactivity, as it's more likely to share electrons or accept electrons rather than lose them to form cations.

12. How does the polarizability of Cl2 compare to other halogens, and what effect does this have on its properties?

Cl2 is more polarizable than F2 but less polarizable than Br2 and I2. This intermediate polarizability affects its reactivity, solubility, and physical properties. For example, it contributes to stronger van der Waals forces compared to F2, resulting in a higher boiling point, but weaker forces than Br2 or I2.

13. How does the dipole moment of Cl2 compare to other molecules containing chlorine?

Cl2 has a dipole moment of zero due to its symmetrical structure and the equal sharing of electrons between identical atoms. This is in contrast to molecules like HCl or ClF, which have significant dipole moments due to the difference in electronegativity between chlorine and the other atom. The lack of a dipole moment in Cl2 affects its solubility and intermolecular interactions.

14. What role do van der Waals forces play in the properties of Cl2?

Van der Waals forces, specifically London dispersion forces, are the primary intermolecular forces between Cl2 molecules. These weak attractive forces contribute to the physical properties of chlorine, such as its boiling point and condensation behavior. They are stronger in Cl2 compared to lighter diatomic gases due to its larger electron cloud.

15. How does the bond length in Cl2 compare to other halogen molecules?

The bond length in Cl2 (198 pm) is longer than that of F2 (142 pm) but shorter than Br2 (228 pm) and I2 (267 pm). This trend is due to the increasing atomic size as you move down Group 17, which affects the overlap of atomic orbitals in the covalent bond.

16. How does the electron configuration of chlorine atoms influence the formation of Cl2?

The electron configuration of a chlorine atom is [Ne]3s23p5. The unpaired electron in the 3p orbital allows for the formation of a covalent bond with another chlorine atom, resulting in the Cl2 molecule. This configuration also explains chlorine's tendency to form a single bond rather than multiple bonds in its elemental state.

17. How does the electronic structure of Cl2 influence its spectroscopic properties?

The electronic structure of Cl2, with its single σ bond and lone pairs, influences its spectroscopic properties. The molecule can undergo rotational and vibrational transitions, which are observable in its infrared and Raman spectra. The presence of lone pairs also affects its UV-visible spectrum, contributing to its characteristic color.

18. How does the bond order in Cl2 compare to other diatomic halogens?

The bond order in Cl2 is 1, indicating a single covalent bond between the two chlorine atoms. This is the same for all diatomic halogens (F2, Br2, I2) in their elemental state. The bond order affects properties such as bond strength and reactivity.

19. How does the molecular mass of Cl2 affect its behavior as a gas?

The molecular mass of Cl2 is approximately 70.9 g/mol. This relatively high mass for a diatomic gas contributes to its density, which is greater than air. As a result, chlorine gas tends to sink and accumulate in low-lying areas, which is an important consideration for safety and handling.

20. How does the polarity of Cl2 compare to other molecules containing chlorine?

Cl2 is a non-polar molecule because it consists of two identical atoms sharing electrons equally. In contrast, many other molecules containing chlorine, such as HCl or ClF, are polar due to the difference in electronegativity between chlorine and the other atom(s) in the molecule.

21. How does the electronegativity of chlorine atoms influence the properties of Cl2?

Chlorine atoms are highly electronegative, which means they have a strong tendency to attract electrons. In Cl2, the equal sharing of electrons between two identical atoms results in a non-polar molecule. However, the high electronegativity contributes to chlorine's reactivity and its ability to form strong bonds with other elements.

22. How does the boiling point of Cl2 compare to other diatomic gases?

The boiling point of Cl2 (-34.6°C) is relatively high compared to many other diatomic gases like H2 or N2. This is due to its larger molecular mass and stronger intermolecular forces (van der Waals forces). The higher boiling point affects its behavior and handling in industrial and laboratory settings.

23. What is the relationship between the structure of Cl2 and its reactivity?

The structure of Cl2, with its single covalent bond and high electronegativity, contributes to its high reactivity. The relatively weak Cl-Cl bond can be easily broken, allowing chlorine to react with many elements and compounds. The presence of lone pairs on each chlorine atom also enhances its ability to act as an oxidizing agent.

24. What is the molecular structure of chlorine gas (Cl2)?

Chlorine gas (Cl2) consists of two chlorine atoms covalently bonded together. The molecule is linear, with the two atoms sharing a single covalent bond. This structure results in a non-polar molecule due to the equal sharing of electrons between identical atoms.

25. Why is chlorine gas yellow-green in color?

The yellow-green color of chlorine gas is due to its absorption of light in the violet region of the visible spectrum. When white light passes through chlorine gas, the violet light is absorbed, and the remaining colors combine to produce the characteristic yellow-green appearance.

26. What is the oxidation state of chlorine in Cl2?

The oxidation state of chlorine in Cl2 is 0. This is because the molecule consists of two identical atoms sharing electrons equally, so there is no net transfer of electrons between the atoms. Each chlorine atom maintains its full complement of seven valence electrons.

27. What role does the octet rule play in the formation of Cl2?

The octet rule is satisfied in Cl2 through the formation of a covalent bond. Each chlorine atom shares one electron with its partner, allowing both atoms to achieve a stable octet (8 electrons) in their outermost shell. This electron configuration contributes to the stability of the Cl2 molecule.

28. What is the significance of chlorine's position in Group 17 of the periodic table?

Chlorine's position in Group 17 (the halogens) indicates that it has seven valence electrons. This electronic configuration makes chlorine highly reactive, as it readily accepts one electron to achieve a stable octet. Its position also influences its properties relative to other halogens, such as reactivity and electronegativity.

29. What is the hybridization of chlorine atoms in Cl2?

The chlorine atoms in Cl2 exhibit sp3 hybridization. Although only one of the four sp3 hybrid orbitals is used for bonding (forming the sigma bond), the other three contain lone pairs. This hybridization contributes to the molecule's geometry and reactivity.

30. How does the Lewis structure of Cl2 relate to its molecular geometry?

The Lewis structure of Cl2 shows a single bond between two chlorine atoms, with three lone pairs on each atom. This structure results in a linear geometry with a bond angle of 180°. The presence of lone pairs doesn't affect the geometry due to the symmetrical distribution around each atom, unlike in molecules like H2O or NH3.

31. How does the presence of antibonding orbitals in Cl2 affect its stability and reactivity?

In Cl2, antibonding orbitals are present but not occupied in the ground state. The presence of these orbitals affects the overall bond order and stability of the molecule. When Cl2 reacts, electrons can be promoted to these antibonding orbitals, weakening the Cl-Cl bond and facilitating reactions, particularly in photochemical processes.

32. What is the significance of chlorine's standard electrode potential in understanding its reactivity?

Chlorine has a high standard electrode potential (E° = +1.36 V for Cl2/Cl-). This positive value indicates that chlorine is a strong oxidizing agent, readily accepting electrons to form chloride ions. This property is crucial in understanding chlorine's reactivity and its applications in various chemical processes.

33. How does the solubility of Cl2 in water affect its properties and uses?

Cl2 is moderately soluble in water, forming chlorine water. This solubility is important for its use as a disinfectant in water treatment. When dissolved, Cl2 undergoes a disproportionation reaction, forming hypochlorous acid (HOCl) and hydrochloric acid (HCl), which contribute to its disinfecting properties.

34. What is the relationship between the molecular structure of Cl2 and its ability to act as a bleaching agent?

The molecular structure of Cl2, with its weak Cl-Cl bond and high electronegativity, allows it to easily decompose in the presence of water to form hypochlorous acid (HOCl). This compound is a strong oxidizing agent that can break down color-causing molecules, making Cl2 an effective bleaching agent.

35. How does the density of Cl2 gas compare to air, and why is this important?

Cl2 gas is about 2.5 times denser than air due to its higher molecular mass. This property causes chlorine gas to sink and accumulate in low-lying areas, which is crucial for safety considerations in handling and storage. It also influences the dispersion patterns of chlorine in the event of a leak.

36. What is the significance of the bond dissociation energy of Cl2 in its chemical behavior?

The bond dissociation energy of Cl2 (242 kJ/mol) is relatively low compared to many other diatomic molecules. This low energy requirement for breaking the Cl-Cl bond contributes to chlorine's high reactivity and its tendency to participate in many chemical reactions, particularly as an oxidizing agent.

37. What is the relationship between the structure of Cl2 and its ability to form addition compounds?

The linear structure of Cl2 and the presence of lone pairs on each chlorine atom allow it to form addition compounds with various unsaturated organic molecules. In these reactions, the Cl-Cl bond breaks, and the chlorine atoms add across double or triple bonds, demonstrating the electrophilic nature of chlorine.

38. How does the presence of isotopes affect the properties of Cl2?

Chlorine has two stable isotopes: 35Cl (75.77%) and 37Cl (24.23%). This results in Cl2 molecules with different masses: 35Cl-35Cl, 35Cl-37Cl, and 37Cl-37Cl. While these isotopic variations don't significantly affect chemical properties, they can be important in precise analytical measurements and in understanding the natural abundance of chlorine compounds.

39. What is the relationship between the structure of Cl2 and its photochemical reactivity?

The Cl-Cl bond in Cl2 can be broken by UV light, producing highly reactive chlorine radicals. This photochemical reactivity is important in atmospheric chemistry, particularly in the depletion of ozone in the stratosphere. The ability of Cl2 to undergo photolysis is related to its electronic structure and the energy of the Cl-Cl bond.

40. What is the significance of chlorine's oxidation states in understanding its chemistry?

Chlorine can exist in oxidation states ranging from -1 to +7. In Cl2, the oxidation state is 0. This range of oxidation states allows chlorine to participate in a wide variety of reactions, both as an oxidizing agent (reducing its oxidation state) and as a reducing agent (increasing its oxidation state in compounds like ClF3 or HClO4).

41. What is the relationship between the structure of Cl2 and its ability to form interhalogen compounds?

The structure of Cl2, with its single covalent bond and high electronegativity, allows it to react with other halogens to form interhalogen compounds. In these reactions, chlorine can act as either the more electronegative or less electronegative element, forming compounds like ClF or ICl. The reactivity is influenced by the relative electronegativity and size of the halogens involved.

42. What is the relationship between the structure of Cl2 and its ability to act as a Lewis acid?

While Cl2 itself is not typically considered a Lewis acid, its structure allows it to act as an electrophile in many reactions. The polarizable Cl-Cl bond can interact with electron-rich species, leading to reactions where the Cl2 molecule accepts electron density. This behavior is important in understanding chlorine's reactivity with unsaturated compounds and in certain inorganic reactions.

43. How does the bond angle in Cl2 compare to other triatomic molecules containing chlorine?

The bond angle in Cl2 is 180°, as it is a linear molecule. This differs from triatomic molecules containing chlorine, such as ClO2 (bent, ~117°) or Cl2O (bent, ~111°). The linear structure of Cl2 is due to the symmetrical distribution of electron density around each chlorine atom, while the bent structures in other molecules result from the presence of lone pairs affecting molecular geometry.

44. How does the molecular mass of Cl2 affect its diffusion rate compared to other gases?

The molecular mass of Cl2 (70.9 g/mol) is relatively high for a diatomic gas. According to Graham's law of diffusion, the rate of diffusion is inversely proportional to the square root of the molecular mass. Therefore, Cl2 diffuses more slowly than lighter gases like H2 or He. This property is important in understanding the behavior of chlorine gas in air and its containment.

45. How does the presence of lone pairs in Cl2 affect its reactivity compared to molecules without lone pairs?

The presence of three lone pairs on each chlorine atom in Cl2 significantly affects its reactivity. These lone pairs make chlorine a good electron donor in certain reactions, allowing