Further Aspects of Bonding (DP IB Chemistry: HL)

Harmful UV radiation from the Sun is absorbed by the ozone layer. 

Explain how the bonding in O₂ and O₃ affects the wavelengths of UV light they absorb

The chemical balance of the stratosphere is disrupted by the presence of chlorofluorocarbons (CFCs) and other ozone-depleting compounds. 

Describe, using equations, how CFCs contribute to ozone depletion using   dichlorodifluoromethane and explain the initial step by reference to the bonds in the CFC.

Although the use of harmful CFCs is being phased out, suggest why these compounds are expected to remain in the atmosphere for the next 80 – 100 years.

Formulate two equations to show how nitrogen(II) oxide, NO, catalyses the destruction of ozone. 

Cyclohexane C₆H₁₂ has a puckered, non-planar shape whereas benzene C₆H₆ is planar. 

Explain this difference by making reference to the C–C–C bond angles and the type of hybridisation of carbon in each molecule.

Urea, CO(NH₂)₂, is present in solution in animal urine. 

What is the hybridisation of C and N in the molecule, and what are the approximate bond angles?

Describe the hybridisation of the carbon atom in methane and explain how the concept of hybridisation can be used to explain the shape of the methane molecule

A molecule of ethanol is shown below.

Deduce the hybridisation of the carbon atom marked in the diagram below.

Carbonation is the process of increasing the concentration of carbonate ions in water to produce carbonated drinks. 

Explain, with the use of diagrams, how there are three valid structures for the carbonate ion.

Describe the distribution of pi (π) electrons and explain how this can account for the structure and stability of the carbonate ion, CO₃^2–.

Identify and explain the bond order of the carbonate ion.

Explain how the concept of hybridisation can be used to explain the triple bond present in propyne.

Consider the molecule below which contains both sigma and pi bonds.

 How many carbon atoms exhibit sp² hybridisation in this molecule.

The concentration of ozone in the upper atmosphere is maintained by the following three reactions, I, II and III

 Explain which reaction requires the most energy

Deduce the hybridisation shown by the nitrogen atoms in NF₄⁺, N₂H₂ and N₂H₄.

	NF4+	N2H2	N2H4
Hybridisation

Sea spray is generated by the breaking of waves and releases bromine into the atmosphere. 

Write two balanced equations to show how a bromine radical could cause the destruction of ozone.

Explain why ozone can be dissociated by light with a longer wavelength than required to decompose oxygen.

The two oxygen-oxygen bonds in ozone are in fact of equal length. Deduce why this is the case and how the length of these would compare to oxygen-oxygen bond lengths in hydrogen peroxide,  H₂O₂, and in the oxygen molecule, O₂

One CFC, Freon-13 (chlorotrifluoromethane), which can be used as a refrigerant, has been phased out by the Montreal Protocol. 

Describe, using equations, the mechanism of the catalysis of ozone depletion by this particular CFC.

 

Sigma (σ) bonds in ibuprofen

Pi (π) electrons in ibuprofen

 

Identify how many sp³ hybrid orbitals are present.

Identify how many sp² hybrid orbitals are present.

 

Write one equation to show the natural formation of ozone in the atmosphere.

Write two equations to show the steps in the natural depletion of ozone in the atmosphere.