Ozone Story Flashcards

1
Q

Convert 339ppm into a percentage

A

399/1 000 000 = 3.99 x 10^-4
Multiply by 100 to get percentage = 0.04%
Or just divide by 10 000

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2
Q

How would you calculate the frequency of light given the wavelength?

A

c = w x f

speed (3 x 10^8) = wavelength x frequency

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3
Q

What four ways can matter react to electromagnetic radiation and what type of radiation causes this?

A

Translation (lowest energy)
Rotation (caused by microwave)
Vibration (caused by infrared)
Electron energy (highest energy - caused by UV and visible light)

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4
Q

Name 3 intermolecular forces

A

Induced dipole bond (van der Waals Forces)
Permanent dipoles
Hydrogen bonding

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5
Q

Explain induced dipole bonding

A

An induced dipole occurs if an unpolarised molecule is next to a dipole, which attracts/repels e- in the unpolarised molecule. Can be induced by a permanent. or induced dipole. Weakest type of intermolecular force. Increases with increasing Mr.

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6
Q

Why do branched alkanes have lower boiling points than straight chain alkanes?

A

Branching means molecules cannot pack as tightly together, weakening the Van Der Waals forces, requiring less energy to break so having a lower bp.

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7
Q

Explain permanent dipoles

A

When atoms in a molecule have different electronegativity, a dipole is formed, often creating a lattice structure

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8
Q

Explain hydrogen bonding

A

The strongest intermolecular force. Only forms between Hydrogen and Nitrogen, Oxygen and Fluorine, the most electronegative atoms. Resulting in a high melting and boiling point.

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9
Q

Define activation energy

A

The minimum energy required for a reaction to take place between colliding particles

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10
Q

What are three benefits of using a catalyst in industrial reactions?

A

Lowers energy cost
Higher atom economy
Increases sustainability (by lowering temp. and energy demand)

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11
Q

Define homogeneous catalysts

A

A catalyst in the same phase as the reactants and products

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12
Q

Why does the shape of the Maxwell-Boltzmann distribution not change even if you change conc. pressure or surface area?

A

Increasing conc., pressure or surface area of reactants means that successful collisions happen more frequently however the energy of individual particles do not change, so the graph does not change shape.

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13
Q

How does the addition of a catalyst affect the Maxwell-Boltzmann distribution?

A

The position of the activation energy shifts to the left so a greater proportion of particles have enough energy to react

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14
Q

Explain what primary, secondary and tertiary haloalkanes are

A

If the carbon bonded to the halogen has a single carbon chain, it is a primary haloalkane, and so on

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15
Q

How does rate of reaction change as you go down group 7 for haloalkanes? Why is this unexpected?

A

Rate of reaction increases as you go down the group, as the greater the Mr of the halogen the lower the bond enthalpy, despite electronegativity decreasing down the group.

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16
Q

Define nucleophile

A

An electron acceptor

17
Q

Explain nucleophilic substitution

A

A nucleophile attacks a haloalkane: attacking the d+ carbon while electrons are transferred to the halogen

18
Q

Define radical

A

A species with an unpaired electron

19
Q

What is homolytic fission?

A

Each bonding atom receives an electron from the bonding pair, forming two radicals

20
Q

What is heterolytic fission?

A

One bonding atom receives both electrons from the bonding pair, forming two ions

21
Q

What are the three stages of the radical mechanism?

A

Initiation: Cl2 –> 2Cl.
Propagation: Cl. + CH4 –> .CH3 + HCl
.CH3 + Cl2 –> CH3Cl + Cl.
Termination: CH3 + CH3 –> C2H6

22
Q

What are the environmental impacts of haloalkanes?

A

UV in stratosphere can cause CFCs (chlorofluorocarbons) to break down into radicals, breaking down ozone

23
Q

Write out the radical mechanism for the breakdown of ozone

A
Overall: 2O3 --> 3O2
Initiation: CF3Cl --> .CF3 + .Cl
Propagation: Cl. + O3 --> .ClO + O2
.ClO + O3 --> Cl. + 2O2
Chlorine radical is regenerated in second step so is catalytic in ozone breakdown
24
Q

Why is ozone important for living organisms?

A

Ozone found mainly in the stratosphere absorbs UV light which can cause cancer and genetic damage

25
Q

What is photochemical smog?

A

Reaction of nitrogen oxides with sunlight and ozone, damaging respiratory systems

26
Q

How is the energy of a frequency of light calculated?

A
E = hv
Energy = Planck's constant x frequency
27
Q

Why are NO and NO2 unusual radicals?

A

They are both stable radicals and can be prepared and. collected like normal substances