Acetylene Formula: Structure, Bond Angle, Dipole Moment, Lewis Structure

Edited By Team Careers360 | Updated on Jul 02, 2025 05:10 PM IST

Acetylene is also known as ethylene. It is the simplest compound in the series of alkynes. It is a known member of the alkyne series that consists of triple bonds. The formula of acetylene is C2H2. It is a colourless gas that is flammable by nature. Its application is as a raw material in the synthesis of organic plastics.

This Story also Contains

The Structure Of Acetylene
Bond Angle
Dipole Moment
Acetylene Lewis Structure

The Structure Of Acetylene

Formula of acetylene

The structure of acetylene can be classified as a hydrocarbon because it consists of carbon and hydrogen atoms. It has two carbons and contains an unsaturated hydrocarbon consisting of a triple bond between the atoms of carbon and two sigma bonds with the hydrogen) atoms.

Eth- is the name of the parent, with "-yne" added as a suffix for triple bonds. Hence, ethyne is the IUPAC name. C2H2 is the chemical formula of acetylene.

The molar mass of acetylene

Use this formula to calculate the molar mass of C2H2

Molecular mass = 2 x (atomic mass of C(carbon) atom) + 2 x (atomic mass of H (hydrogen atom))

= 2 X (12.010)+ 2 X (01.007) = 26.040 g per mol

Hence, 026.040 g is the weight of 1 mole of acetylene formula.

Acetylene hybridization

Each carbon atom has sp-hybridization in ethyne. In the ground state of carbon, there are two electrons in the 2s orbital and one electron each in the 2Px and 2Py orbitals. 2Pz orbitals are empty. However, in its excited state, the paired electron pops out of the 2s orbital and fills the empty 2Pz orbital. So there are four orbitals 2s, 2Px, 2Py and 2Pz which are individually paired and willingly accept electrons from other atoms. However, there is a difference in how they overlap. In sp-acetylenic hybridization, the single electrons present in the 2Py and 2Pz orbitals are not hybridised. Instead, they overlap laterally with the unhybridized 2Pz and 2Py atomic orbitals of another carbon atom.

This forms a C-C triple bond. It includes the following:

1. The sigma (σ) bond is formed by the carbon atoms overlapping sp orbitals.

2. Pi (π) bonds are formed when unhybridized 2py orbitals overlap laterally.

3. Pi (π) bonds are formed by the lateral overlap of unhybridized 2Pz orbitals.

This 2sp hybrid orbital of ethyne (C2H2) forms a linear structure with a bond angle of 180 degrees.

Molecular Geometry

All the atoms present in ethyne lie in the same plane. There is no asymmetry present in the molecule. Therefore, C2H2 has a linear molecular geometry.

Bond Angle

Acetylene is an example of an unsaturated hydrocarbon. This is due to the triple bond formed by its two carbon atoms. The carbon-carbon triple bond results in the placement of all four atoms in the same straight line. As a result, acetylene has a bond angle of 180o.

Dipole Moment

C2H2 is composed of two types of atoms: carbon and hydrogen. The electronegativity difference between carbon and hydrogen is approximately 0.35, less than 0.4. Therefore, the C-H bond is nonpolar. Moreover, the atoms of ethyne are arranged linearly, so the distribution is uniform on both sides. Therefore, even if there is a dipole moment, it will be cancelled because the direction is opposite. Therefore, ethyne is a non-polar molecule.

Acetylene Lewis Structure

An atom of carbon has four valence electrons in its outer shell. Ethyne has two carbon atoms. Therefore, the carbon atom of C2H2 has eight valence electrons. An atom of hydrogen has one valence electron that is present in its outer shell. Therefore, a hydrogen atom has two valence electrons.

C2H2 valence electrons = 8 + 2 = 10

The C2H2 molecule has 10 valence electrons.

In the Lewis structure, both carbon atoms are centred because the carbon atom has a higher valence than the hydrogen atom. So two carbon atoms occupy the central position, and hydrogen atoms are arranged around them. Both the hydrogen atoms will have to share one valence electron of the carbon atom to form a bond.

The couple of both hydrogen atoms is complete now, but the octet of carbon atoms is not yet complete. So, to attain a structure that is stable, the carbon atom will have to share the three valence electrons that are remaining with the help of a triple bond. A total of six valence electrons out of 10 valence electrons are used to form a triple bond. It is formed between carbon atoms. In the Lewis structure of C2H2, the octets of all the atoms are completely filled, and no lone pairs of electrons are left in the molecule.

Frequently Asked Questions (FAQs)

1. Can you write about the Acetylene Formula Structure?

Eth- is the name of the parent, with "-yne" added as a suffix for triple bonds. Hence, ethyne is the IUPAC name with "-yne" added as a suffix for triple bonds. Hence, ethyne is the IUPAC name. C2H2 is the chemical formula of acetylene.

2. What is the molar mass of acetylene?

Use this formula to calculate the molar mass of C2H2.

The atomic mass of the C (carbon) atom plus the atomic mass of the H (hydrogen) atom equals the molecular mass.

= 026.040 g per mol = 02.000*(12.010) + 02.000*(01.007)

Hence, 026.040 g is the weight of 1 mole of the acetylene formula.

3. What is the bond angle of the acetylene formula?

Acetylene is an example of an unsaturated hydrocarbon. This is due to the triple bond formed by its two carbon atoms.The carbon-carbon triple bond results in the placement of all four atoms in the same straight line. As a result, acetylene has a bond angle of 180°.

4. Tell us about the Lewis structure of the acetylene formula

5. What is the acetylene formula's dipole moment?

6. How many sigma and pi bonds are present in acetylene?

Acetylene contains three sigma (σ) bonds and two pi (π) bonds. The sigma bonds include two C-H bonds and one C-C bond, while the two pi bonds form the triple bond between the carbon atoms.

7. What is the hybridization of carbon atoms in acetylene?

The carbon atoms in acetylene are sp hybridized. This hybridization allows for the formation of a linear molecule with a 180° bond angle.

8. Why is the acetylene molecule linear?

Acetylene is linear because of the sp hybridization of its carbon atoms. The sp hybrid orbitals are arranged 180° apart, resulting in a linear geometry with the hydrogen atoms at opposite ends of the molecule.

9. How does the triple bond in acetylene affect its reactivity?

The triple bond in acetylene makes it highly reactive. The pi electrons are easily accessible, allowing acetylene to participate in addition reactions, forming various products with different functional groups.

10. What is the Lewis structure of acetylene?

The Lewis structure of acetylene shows two carbon atoms connected by a triple bond (one sigma and two pi bonds), with each carbon also bonded to a hydrogen atom. It can be represented as H-C≡C-H.

11. What is the bond angle in acetylene?

The bond angle in acetylene is 180°. This is due to the linear arrangement of the atoms resulting from the sp hybridization of the carbon atoms.

12. What is the significance of acetylene's sp hybridization in its structure?

The sp hybridization of carbon atoms in acetylene results in a linear geometry and allows for the formation of a triple bond. This hybridization explains the molecule's 180° bond angle and its unique reactivity.

13. What is the importance of acetylene's linear structure in its industrial applications?

The linear structure of acetylene, resulting from sp hybridization, contributes to its high reactivity and ability to form various products. This makes it valuable in industrial synthesis, particularly in the production of plastics and other organic compounds.

14. How does the structure of acetylene affect its spectroscopic properties?

The linear structure and triple bond of acetylene give it unique spectroscopic properties. In infrared spectroscopy, it shows characteristic C-H stretching at high frequencies, while in UV-vis spectroscopy, the pi electrons can undergo electronic transitions.

15. What is the relationship between acetylene's structure and its ability to participate in cycloaddition reactions?

The pi electrons in acetylene's triple bond make it an excellent dienophile in cycloaddition reactions, such as the Diels-Alder reaction. The linear structure allows for good orbital overlap with dienes, facilitating these reactions.

16. Does acetylene have a dipole moment?

No, acetylene does not have a dipole moment. Despite having polar C-H bonds, the symmetrical linear structure of the molecule results in the dipoles canceling each other out, making the overall molecule non-polar.

17. How does the structure of acetylene influence its solubility in water?

Despite being a hydrocarbon, acetylene has slightly higher solubility in water compared to other hydrocarbons. This is due to the polarizable nature of the triple bond, which can interact weakly with water molecules.

18. How does the structure of acetylene affect its boiling point compared to other hydrocarbons?

Despite its small size, acetylene has a relatively high boiling point compared to other small hydrocarbons. This is due to the presence of easily polarizable pi electrons in the triple bond, which can form weak intermolecular forces.

19. How does the electron density in acetylene differ from other hydrocarbons?

Acetylene has a high concentration of electron density along the axis between the two carbon atoms due to the triple bond. This creates an electron-rich region that contributes to its reactivity and unique chemical properties.

20. What role does acetylene's structure play in its use as a fuel?

Acetylene's triple bond contains a high amount of energy. When burned, this bond breaks, releasing significant heat. The linear structure also allows for efficient combustion, making it suitable as a fuel for welding and cutting torches.

21. What is the molecular formula of acetylene?

The molecular formula of acetylene is C2H2. This means it contains two carbon atoms and two hydrogen atoms.

22. Why is acetylene considered a hydrocarbon?

Acetylene is considered a hydrocarbon because it is composed only of carbon and hydrogen atoms. All compounds containing only carbon and hydrogen are classified as hydrocarbons.

23. What type of hydrocarbon is acetylene?

Acetylene is an alkyne, which is a type of hydrocarbon characterized by the presence of at least one carbon-carbon triple bond.

24. Why is acetylene also called ethyne?

Acetylene is also called ethyne because it follows the systematic IUPAC naming convention for alkynes. The "-yne" suffix indicates the presence of a triple bond, and "eth-" represents the two-carbon chain.

25. How does the structure of acetylene contribute to its high energy content?

The triple bond in acetylene is highly energetic due to the concentration of electrons between the carbon atoms. When acetylene burns or reacts, breaking this bond releases a significant amount of energy, contributing to its high energy content.

26. How does the bond length in acetylene compare to other hydrocarbons?

The C-C bond in acetylene is shorter than in alkenes (double bond) and alkanes (single bond). This is due to the triple bond, which pulls the carbon atoms closer together, resulting in a bond length of about 120 picometers.

27. Why is acetylene considered unsaturated?

Acetylene is considered unsaturated because it contains a carbon-carbon triple bond. Unsaturated hydrocarbons have at least one double or triple bond, allowing them to potentially add more hydrogen atoms or other groups.

28. Why is acetylene more acidic than other hydrocarbons?

Acetylene is more acidic than other hydrocarbons because the sp-hybridized carbon atoms can better stabilize the negative charge of the conjugate base (acetylide ion). This is due to the higher s-character of sp orbitals compared to sp2 or sp3 orbitals.

29. How does the bond order in acetylene compare to other hydrocarbons?

Acetylene has a bond order of 3 between its carbon atoms, higher than the bond order in alkenes (2) and alkanes (1). This higher bond order contributes to acetylene's shorter bond length and greater bond strength.

30. Why does acetylene undergo addition reactions more readily than substitution reactions?

Acetylene undergoes addition reactions more readily due to its triple bond. The pi bonds are electron-rich and accessible, making it easier for reagents to add across the triple bond rather than substitute the hydrogen atoms.

31. How does the structure of acetylene contribute to its ability to form polymers?

The triple bond in acetylene can be opened up through various reactions, allowing the molecule to form new bonds. This reactivity enables acetylene to participate in polymerization reactions, forming long chains or complex structures used in various materials.

32. What is the relationship between acetylene's structure and its flame temperature?

Acetylene's triple bond contains a high amount of energy. When burned, this energy is released, resulting in an extremely hot flame. The linear structure also allows for efficient combustion, contributing to the high flame temperature.

33. How does the electronegativity difference between carbon and hydrogen affect the electron distribution in acetylene?

The small electronegativity difference between carbon and hydrogen results in a slight polarization of the C-H bonds. However, due to the molecule's symmetry, these dipoles cancel out, leaving acetylene as a non-polar molecule overall.

34. Why is acetylene capable of forming metal acetylides?

Acetylene can form metal acetylides because of its slightly acidic nature. The sp-hybridized carbons allow the hydrogen atoms to be removed relatively easily, forming an acetylide ion that can bond with metal ions.

35. How does the structure of acetylene influence its stability?

Acetylene is less stable than many other hydrocarbons due to its high energy triple bond. This makes it more reactive and prone to decomposition, especially under pressure or at high temperatures.

36. What role does orbital overlap play in the bonding of acetylene?

In acetylene, the sp hybrid orbitals of carbon overlap end-to-end to form the sigma bond, while the unhybridized p orbitals overlap side-by-side to form the two pi bonds. This efficient orbital overlap contributes to the strength of the triple bond.

37. Why does acetylene have a positive heat of formation?

Acetylene has a positive heat of formation because it requires energy to form from its elements. The triple bond is high in energy, making the molecule less stable than the elemental carbon and hydrogen it's made from.

38. How does the structure of acetylene contribute to its use as a chemical feedstock?

Acetylene's reactive triple bond makes it an excellent starting material for many organic syntheses. It can undergo various addition reactions to form a wide range of products, making it valuable as a chemical feedstock in industry.

39. What is the significance of acetylene's bond dissociation energy?

The bond dissociation energy of acetylene's triple bond is very high, reflecting the strength of the bond. This high energy contributes to acetylene's reactivity and its ability to release significant energy when the bond is broken during reactions.

40. How does the structure of acetylene affect its behavior in addition polymerization?

The triple bond in acetylene can open up during addition polymerization, allowing the molecule to form new bonds with other monomers. This can lead to the formation of polymers with conjugated double bonds, which have interesting electrical and optical properties.

41. Why does acetylene form complexes with transition metals?

Acetylene can form complexes with transition metals due to its ability to act as a ligand. The pi electrons in the triple bond can donate electron density to empty orbitals on metal atoms, forming stable coordination compounds.

42. How does the structure of acetylene contribute to its explosive nature under certain conditions?

Acetylene's triple bond contains a high amount of energy. Under high pressure or in the presence of certain catalysts, this energy can be released rapidly, leading to explosive decomposition. The linear structure also allows for rapid propagation of the reaction.

43. How does the electron configuration of acetylene contribute to its pi-stacking abilities?

The pi electrons in acetylene's triple bond are delocalized above and below the molecular axis. This electron distribution allows acetylene to participate in pi-stacking interactions with other molecules that have pi systems, contributing to its intermolecular forces.

44. Why does acetylene have a lower boiling point than ethylene despite having more electrons?

Although acetylene has more electrons than ethylene, its linear structure results in weaker intermolecular forces. Ethylene's bent structure allows for stronger van der Waals interactions between molecules, leading to a higher boiling point.

45. How does the structure of acetylene influence its behavior in electrophilic addition reactions?

The electron-rich triple bond in acetylene makes it susceptible to electrophilic addition reactions. The linear structure allows electrophiles to approach from either side of the molecule, leading to the formation of various addition products.