928094
Description
Flashcards by joannalivesey, updated more than 1 year ago
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Created by joannalivesey
over 11 years ago
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| Question | Answer |
| Problems with working at high pressure | • danger of explosions • expensive: lots of energy needed to run compressor/ thick walls of the specialised plant are expensive |
| Ionic properties | • high melting point- strong electrostatic forces between neg and pos ions •dissolves in water- ions are hydrated, they form ion-dipole bonds with water •conducts electricity when in solution/molten - free ions can MOVE |
| Raw and feedstock materials for haber process | • raw: air and natural gas • feedstock: nitrogen and hydrogen |
| Why is ammonium nitrate a good fertiliser? | • High % nitrogen - nitrogen needed by plants to make proteins etc • Soluble • NH4+ held by clay in the soil |
| Uses of nitric acid | • Making fertilizers • Making dyes • Making explosives |
| Effect of temp on rate | • molecules have more KE so collide more frequently • With energy greater than activation enthalpy |
| Why use a high-ish temp if forward reaction is exothermic? | Compromise between rate and yield |
| Problems with NO(g) | • toxic (respiratory problems) • gives rise to acid rain • photochemical smog • greenhouse gas |
| Why is nitrogen hard to fix? | • Nitrogen is very unreactive with a high Ea • Strong triple bond between the N atoms that needs a lot of energy to break |
| Explain the circle in a benzene ring | • delocalised electrons • one electron from each carbon • two rings of electrons • above and below carbon ring |
| Why are azo compounds coloured? | • Presence of a chromophore- an extended delocalised system • Compound absorbs in the visible region • Complementary colour to the one absorbed gets transmitted (what we see) |
| What is meant by ‘delocalisation’? | • Electrons are not associated with one bond • Instead, they are spread over several atoms (NOT whole molecule!) |
| Effect of increasing length of chromophore of a molecule | • Decreases the frequency of light absorbed • Lower excitation energy • smaller distance between energy levels (E=hv) • greater intensity of absorption |
| Conditions for Haber process | 450 ˚C, 200 atm, iron catalyst |
| Causes of acid rain | • power stations • burning of fuels containing sulfur • NOx produced in high T+P of car engines |
| Problems of acid rain | • attacks buildings • damages trees/plants • damages/kills fish • causes respiratory problems |
| What is standard enthalpy change of formation? | enthalpy change when one mole of the compound is formed from its elements under standard conditions, and with everything in its standard state |
| Why is benzene colourless? | stable molecule so absorbs in UV region (higher frequency than visible) |
| What is the SO3- functional group called? Why does it increase solubility of an azo dye? | • sulfonate • ions are readily hydrated by water molecules |
| how do buffers work? | • Maintain a constant pH despite small additions of acid or alkali • Acid is H+, alkali is OH- • (on adding acid) equilibrium moves to left to remove H+ • (on adding alkali) equilibrium moves to right and forms H+ to neutralise OH- • Because [salt] and [acid] are large, pH remains constant |
| How can impurities poison a catalyst? | • Impurity binds to catalyst surface • prevents reactants adsorbing to catalyst surface |
| How could you alter the colour of something with a chromophore? | • Add functional group; e.g. NH2, OH, to change the conjugation • Add more double bonds; to extend the conjugated system • Change position of side chains around a benzene ring; e.g. to 1:2 or 1:3 • Change configuration of C=C; to make the cis/trans form |
| why is Al3+ more hydrated than Na+? | • higher CHARGE DENSITY (larger core charge and smaller ionic radii) • attracts more water molecules |
| Describe the chlorination of benzene mechanism | • AlCl3 further polarises C-Cl bond to create Cl+ and AlCl4- • the Cl+ acts as an electrophile and attacks the benzene • H+ is released from the benzene and AlC3 is reformed (H+ + AlCl4- -> HCl + AlCl3) |
| why does benzene undergoes substitution reactions, rather than addition reactions? | • benzene has a delocalised system of electrons which makes it stable • delocalisation is retained in substitution reactions (so stability is retained) • addition product is less stable as delocalisation is lost |
| why convert a compound into a salt to be used as the herbicide? | much more soluble |
| why does increasing pressure increase rate? | • molecules in smaller volume • more frequent collisions |
| talking about reflectance spectrums (e.g. if compound is blue) | • reflects only blue • absorbs all other colours |
| why is oleic acid insoluble in water? | • hydrogen bonds are broken in water • id-id bonds are broken in oleic acid • id-id bonds are made between oleic acid and water • more energy required to break bonds than make them |
| weak acid assumptions | • [H+] = [A–] (all H+ comes from acid) • initial [HA] = equilibrium [HA] |
| difference between co-product and by-product | • co-product is formed in the reaction that produces the main product • by-product is formed by side/unwanted reactions |
| advantages of a high atom economy? | little waste as most atoms used |
| what is a pharmacophore? | part of the molecule that is responsible for the medicinal action (e.g. binds to an active site) |
| WHAT DO YOU NEED TO GO OVER AND CHECK?????? | - SIGNS OF ENTHAPLY/ENTROPY STUFF - IF ARROWS SHOULD BE DRAWN AS EQUILIBRIUM ARROWS OR NORMAL ONES!!! |
| why will diazonium salts not react with benzene, only phenol/phenyl amine? | The diazonium salt is a relatively weak electrophile and will only react with particularly electron-rich activated benzene rings |
| why is CO2 not polar? | • dipoles cancel • centre of negative charge is on the centre of positive charge |
| sequence of events from plant fungus to drug | • show that a compound has medicinal properties • clinical trials • identify pharmacophore •synthesise similar molecules |
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