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47 Cards in this Set
- Front
- Back
What are the uses for CFCs
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-Refrigerants
-Propellants in aerosols -Blowing agents |
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What happens when CFCs reach the stratosphere?
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They undergo photodissociation to produce chlorine radicals, which go onto remove ozone
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Advantage of HCFCs (a CFC replacement)
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H-C bonds are broken down in troposphere before the compounds have chance to reach the stratosphere
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Disadvantage of HCFCs
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Greenhouse gasses that contribute to global warming
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how can the amount of CO2 in the atmosphere he reduced?
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-Reducing the consumption of fossil fuels
-using alternate energy fuels -increasing photosynthesis -burying or reacting CO2 |
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When molecules absorb infrared radiation what happens?
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-Vibrational energy increases
-Energy is transfered to other molecules through collisions -This increases their kinetic energy raising the average temperature of the atmosphere |
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What is diamonds structure?
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Each C atom is joined tetrahedrally to four other C atoms by strong covalent bonds
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Why is CO2 a gas at room temperature, while SiO2 is a solid?
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-CO2 has weak intermolecular bonds
-SiO2 has a giant network structure = more energy to overcome bonds |
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why is CO2 soluble in water, while SiO2 is insoluble?
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-CO2 has polar bonds
-Water can't break the giant structure of SiO2 |
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What are the three part of the atmosphere?
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Ionosphere
Stratosphere Troposphere |
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To convert ppm to % you...
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÷10000
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What are the different types of energies in order of increasing energy?
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Translational
Rotational Vibrational Electronic |
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What are type of radiation is associated with each type of energy?
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Translational-
Rotational- Microwave Vibrational- Infrared Electronic- ultraviolet |
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E = hv
what does each letter represent |
E = energy
h = planck constant (6.63×10^-34) v = frequency |
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One of the things that can happen when a molecule absorbs visible or UV radiation
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Electrons can be excited to a higher electronic energy level; the electrons will return to their original energy levels in time, releasing the energy that has been absorbed
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Another thing that can happen when a molecule absorbs visible or UV radiation
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Chemical bonds can break and radicals form (this is called photodissociation)
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The last things that can happen when a molecule absorbs visible or UV radiation
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An electron is ejected from a molecule which then becomes ionised
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What does a curly arrow represent
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Indicates the movement of two electrons
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What is a radical
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A species with one or more unpaired electrons
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What is heterolytic fission
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Both the electrons of the shared pair goes to just one of the atoms when the bond breaks
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What is homolytic fission
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-One of the two electrons in he shared pair goes to each of the atoms
-both atoms now have one unpaired electron -radicals have been formed |
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An initiation reaction is when...
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There are no radicals at the beginning of this stage but radicals are formed by the end of the stage
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A propagation reaction is when...
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There are radicals at the start of this stage, and new radicals are formed by the end of the stage
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A termination reaction is when...
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The reaction is terminated when two radicals collide
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An equation for the formation of ozone
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O + O2 ---> O3
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Two equations that show ozone being lost
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X + O3 ---> XO + O2
XO + O ---> O2 + X |
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Why is the depletion of ozone a problem?
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-Ozone absorbs UV radiation
-this is very damaging to the skin -a lot of the UV radiation us absorbed by ozone in the stratosphere -reducing skin damage |
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Define dynamic equilibrium
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When the rate of the forward reaction is the same as the rate of the backwards reaction
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Two equations for the production and destruction of ozone
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Production O + O2 ---> O3
Destruction O3 --(hv)-> O2 + O Destruction O + O3 ---> O2 +O2 |
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What does Le Chatelier's principle state
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If a system is at equilibrium, and a change is made in any of the conditions, then the system responds to counteract the change as much as possible
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Where will the equilibrium shift if the concentration of the reactants increases
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To the right (decreases the reactants)
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Where will the equilibrium shift if the concentration of the products increases
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To the left (decreases products)
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Where will the equilibrium shift if the concentration of the reactants decreases
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To the left (increases reactants)
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Where will the equilibrium shift if the concentration of the products decreases
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To the right (increases products)
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If the pressure increases where will the equilibrium shift
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To the side with fewer gas molecules
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If the pressure decreases which way will the equilibrium shift
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To the side with more has molecules
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If the temperature increases which way will the equilibrium shift
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Shift in the direction of the endothermic reaction
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If the temperature decreases which way will the equilibrium shift
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Shift in the direction of the exothermic reaction
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There are seven ways to affect a rate of reaction, name some
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-Concentration
-Pressure -A catalyst -Intensity of reaction -Surface area -particle size -temperature |
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What is the collision theory
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Reactions occur when particles of reactants collide with a certain minimum kinetic energy
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How does increasing concentration and pressure affect rate of reaction
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The particles are in closer proximity to each other encouraging more frequent collisions
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How does increasing temperature affect the rate if reaction
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-A higher proportion of colliding particles have sufficient energy to react
-More particles are able to overcome the activation enthalpy barrier |
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How does increasing surface area affect rate of reaction
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Larger surface area on which the reactions can take place, greater chance of successful collisions
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The activation enthalpy is...
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the minimum kinetic energy required by a pair of colliding atoms or molecules before a reaction will occur
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How do catalysts work?
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By providing an alternate pathway for the breaking and making of bonds. This alternate pathway has a lower activation enthalpy
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How does a homogeneous catalyst work?
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-The activation enthalpy barrier is overcome and an intermediate is formed
-The intermediate breaks down to give a product and reform the catalyst |
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How does a heterogeneous catalyst work?
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They provide a surface on which the reaction may take place, thus lowering the energy needed for a successful collusion
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