the ozone story Flashcards
What is electronegativity?
The ability of an atom to attract bonding electrons in a covalent bond.
How does electronegativity vary across the periodic table?
It increases across a period and up a group, towards fluorine.
What causes a bond to be polar?
A difference in electronegativity greater than 0.4 between two atoms.
What is a dipole?
A separation of charge that occurs due to a polar bond.
What makes a molecule polar?
An overall dipole moment due to uneven charge distribution that doesn’t cancel out.
When is a molecule non-polar despite having polar bonds?
When polar bonds are arranged symmetrically and cancel each other out.
What are instantaneous dipole-induced dipole bonds?
Weak forces formed by temporary dipoles due to electron movement in all molecules.
How does chain length affect id-id bonds?
Long chains have more surface area and form stronger id-id bonds.
How does branching affect id-id bonds?
Branched chains can’t pack closely, reducing the number of id-id bonds formed.
What are permanent dipole-permanent dipole bonds?
Attractive forces between molecules with permanent dipoles, in addition to id-id forces.
What are hydrogen bonds?
Strong dipole-dipole attractions when hydrogen is bonded to O, N, or F.
Why is ice less dense than water?
Because ice forms a structure that maximizes hydrogen bonding, creating more open space.
What does collision theory state about chemical reactions?
Particles must collide with the correct orientation and sufficient energy (activation energy).
How does temperature affect the Boltzmann distribution?
At higher temperatures, more particles have energy ≥ activation energy and collide more frequently.
What is a homogeneous catalyst?
A catalyst in the same state as the reactants that lowers activation energy by forming intermediates.
How does a homogeneous catalyst affect the enthalpy profile?
It creates an alternative pathway with two activation energy peaks.
How does boiling point change in haloalkanes down the group?
Boiling point increases due to greater atomic mass and stronger id-id forces.
What is nucleophilic substitution?
A reaction where a nucleophile replaces a halogen in a haloalkane.
What are the conditions for haloalkane reaction with sodium hydroxide?
Warm, aqueous sodium hydroxide under reflux.
How can haloalkanes react with ammonia?
Warm with excess ethanolic ammonia to form amines.
How does reactivity of haloalkanes change down the group?
It increases down the group due to weaker C-X bonds (easier to break).
What is homolytic fission?
Breaking a bond evenly to form two radicals.
What is heterolytic fission?
Breaking a bond unevenly to form a cation and an anion.
What are the stages of a chain reaction?
Initiation (radicals formed), Propagation (radicals react forming more radicals), Termination (radicals combine).
How do halogen radicals react with alkanes?
They form haloalkanes via photodissociation and radical substitution.
How is ozone formed in the stratosphere?
O₂ reacts with O radicals formed by photodissociation to form O₃.
What causes ozone to break down?
UV radiation causes photodissociation of ozone, forming O₂ and O radicals in an equilibrium.
Why is the ozone layer important?
It absorbs harmful UV radiation, protecting living organisms.
What are the types of UV radiation?
UVA (lowest energy), UVB (causes sunburn and skin cancer), UVC (absorbed by ozone).
What is the impact of ground-level ozone?
It contributes to photochemical smog and causes respiratory issues.
How do CFCs affect the ozone layer?
C-Cl bonds are broken by UV light, forming Cl radicals that catalyze ozone breakdown.
What is the role of nitrogen oxides in ozone depletion?
NO₂ absorbs UV and forms NO and O, which participate in ozone breakdown.
What happens when a molecule absorbs UV or visible light?
Electrons are excited to higher energy levels; enough energy can break bonds and form radicals.
What is the equation for energy of radiation?
E = hv (E = energy, h = Planck’s constant, v = frequency).
What is the equation for frequency of radiation?
v = c/λ (v = frequency, c = speed of light, λ = wavelength).
