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42 Cards in this Set

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Explain what is meant by the term dynamic equilibrium.

rate of forward reaction = rate of back reaction




concentrations of reactants and products remain constant / closed system (1) ;

The organic product forms as an impure liquid. Describe how the student could remove the acidic impurities from the liquid.

(shaking with) sodium hydrogencarbonate (solution) (1) ;

Name two ways of reducing the amount of carbon dioxide in the atmosphere, other than storing it under the ocean.

burn less fossil fuel (1) ;named alternative power source (1) ;less deforestation / plant more trees (AW) / more photosynthesis (1) ;reacting the CO2 with lime/other suitable named solid (1)

Use the mechanism shown in (ii) to explain why both these compounds are formed.

)carbocation / intermediate 1 is attacked by nucleophiles / species carrying negative charge /




both Br- and Cl– attack carbocation / intermediate 1 (1)




attack by Br– gives compound A / Attack by Cl– gives compound B (1)

Explain what is meant by the term electrophile and how the electrophile attacks the alkene

(partially) positively charged/ electron deficient reagent (AW) (1) ;bonds by accepting a pair of electrons (1) ;

Explain what is meant by the term radical

(A particle) with one (or more) unpaired electron(s).

IR 6 marker

-Sun emits UV-Earth absorbs some of the energy (from the Sun)-Earth re-emits IR-CO2 absorbs IR radiation-Making bond vibrate (more)-Turned into kinetic energy that raises the temperature-Some CO2 molecules re-emit/radiate IR which warms Earth-More CO2 means a greater temperature increase/greater enhanced greenhouse effect

Explain how chlorine causes ozone depletion in the stratosphere & suggest why bromomethane has a lower ozone depleting potential than chloromethane

Chloromethane is not broken down in the troposphere/unreactive




But is broken down/photodissociates in the stratosphere




by high frequency UV radiation




Breakdown of chloromethane produces chlorine free radicals which catalyzes the breakdown of ozone




C-Br bond weaker than C-Cl so molecule reacts in the troposphere before reaching the stratosphere

How do id-id bonds form?

Electron movements create an uneven distribution of charge




A dipole is induced in a neighbouring molecule leading to attraction

Why are chlorine atoms more readily reduces than iodine atoms?

Because chlorine atoms are smaller than iodine & so have a greater nuclear charge so the extra electron gained is more strongly attracted to the positive nucleus than with iodine

Give an e.g. of a human activity that gives rise to oxides of nitrogen

Burning fuel in vehicle engines/driving a vehicle

Describe how the rate of reaction varies under temperature conditions

Rate is greater when the temperature is higher




At higher temperatures particles have more energy/move faster




More frequent collisions




Which thus leads to more successful collisions/more collisions have (total) energy of atleast the Activation energy





Suggest why it still occurs slowly in the atmosphere even if it has a low activation energy/enthalpy

Few collisions

Suggest why this reaction has a low bond enthalpy

No bond breaking

Explain why a reaction is faster in the presence of a catalyst

Catalyst's provide an alternative route with a lower activation energy

Explain how the presence of ozone in the stratosphere benefits us

Ozone stops/blocks out high frequency UV radiation which could otherwise damage DNA

Pros & cons of (tropospheric) ozone

Pro: Blocks out high frequency UV radiation which could otherwise damage DNA




Con: Causes photochemical smog

What is heating under refluex

To boil a liquid in a container attached to a vertical/upright condenser

Why heating under reflux is used/pros

Increases rate of reaction




Allows boiling for a long time




Stops loss of reactants and or products/volatiles




Stops liquids catching fire

What is meant by ultraviolet dissociation of a molecule

UV of high frequency causes the bonds in a molecule to break/causes photodissocation to form form free radicals




Breaks homolytically...?

Describe how ____ can be separated from an aq layer

Put into a separating funnel




Pipette of the top or the water layer

Explain why _____ is classified as a nucleophile

It is a negative ion with a lone pair & can be donated/available to form a bond

Thermoplastic

Soften/melts/deforms when warmed/heated

Surface area effect (reaction rates)

Finely divided powder (e.g.) = greater surface area of the catalsyt




So more frequent collisions





Explain why ____ is slightly soluble in water, but _____ is insoluble

______ can form hydrogen bonds with water




whereas ______ cannot form hydrogen bonds with water

How do hydrogen bonds arise?

Oxygen small & electronegative/lone pair on oxygen




attracted to hydrogen with a partially positive charge/s+ charge






*Note that O could also be N or F since hydrogen bonding only happens when H is bonded to either one of NOF*

Describe the structure/bonding of diamond

Giant network/giant lattice




with every C bonded to four other Cs/ every C is tetrahedrally bonded




Covalent

Describe the evidence for the relationship between the increased concentration of greenhouse gases & global warming

There is a relationship between models of gas & models of temperature

Describe the theoretical work that led to the research of ozone depletion in the stratosphere & how the evidence was originally overlooked

Prediction/discovery (in the lab) that Cl can damage the ozone layer




Spectroscopic measurements showed ozone levels depleted/ lower than expected




results initially overlooked as the values were too small & so they thought that it was an error

Describe & explain why the ozone is important to humans & the natural processes by which ozone is formed in the stratosphere

Blocks high frequency UV radiation which would other wise damage DNA, damages immune system, damages eyes, affects crops, cell mutations (any 3)




UV radiation causes the photodissociation of oxygen molecules which forms oxygen radicals




These radicals can then react with an oxygen molecule/O2 to form ozone





Why ____ is only slightly soluble in water

Hydrogen bonds between ____ are weaker than the water-water interactions

Explain why ____ can exist as 2 E/Z isomers

_____ has a C=C double bond




with different groups on each carbon of the C=C

What is the fingerprint region

Region to the right of 1500cm^-1




Unique part of the spectrum for a molecule




Can be used to identify the molecule





How halogenoalkanes deplete ozone

Halogenoalkanes break down in the presence of high frequency UV radiation to form radicals




These radicals catalyze the breakdown of ozone












*Low ozone concentrations were found in the arctic* = evidence for ozone depletion

The molecule is polar because

The charges do not balance




e.g. CF3Cl




+ C-F bond is more polar than the C-Cl bond



Type of EM radiation emitted from the Earth's surface

Infrared radiation

Propagation

One radical is used up & is replaced by another

Homolytic fission

One electron from the bond goes to each atom

Define initiation

Movement of a single electron

Define termination

When 2 free radicals join together, they make a stable molecule

Explain how infrared spectroscopy produces a spectrum for a compound & how the spectrum would confirm the presence of (e.g. carbon & hydrogen) in the product.

Bonds absorb IR radiation




Absorption of IR of a particular range of frequencies




Causing vibration/bending/stretching




Spectrum shows peaks where the absorption has occurred




No peaks for bonds involving atoms other than C & H

Explain why ____ have the partial charges you have shown in...

E.g. This is because both fluorine & chlorine are more electronegative than carbon




So therefore both fluorine & chlorine have a greater ability to attract the bonding electrons than does carbon