describe what happens to the vapour when a mixture is heated under reflux

reasons why to reflux

describe and explain the process of recrystallisation using a suitable solvent. Include an explanation for the choice of solvent used and how impurities are removed

explain why a substance produces a spectrum showing absorption peaks when irradiated with infrared frequencies

give the meaning of the term Tg

the less crystalline the polymer the more flexible - explain why

when using potassium manganate (VII) in a titration why do you not need to add an indicator?

as a reaction progresses, ions are formed which acts as a catalyst. explain the changes in the reaction rate as the reaction progresses

suggest a method that can be used to measure the concentration of a substance other than by titration

explain the term zwitterion

drug x has many adverse side effects. suggest why it is still used to treat a disease

explain why with 1,2-diaminocyclohexane, you may have two different isomers

describe the three levels of protein structure

what data would you need in order to be able to comment on the effect of temperature on the value of the equilibrium constant?

explain why, in a reversible reaction in which a solid is formed, the reaction almost goes to completion

what feature of d-block metal ions enables some to be coloured in solution?

name a suitable acid to acidify a sample for titration purposes

suggest one advantage natural fibres have over polymers in terms of the method of disposal

explain why hydrogen bonding is strong when there are benzene rings in the chain

explain why transition metals can act as catalysts

suggest four possible ways of monitoring the rate of a reaction

when concentrated sulphuric acid is used to catalyse a reaction, the yield of the product increases - why?

explain why the polymerisation of compound D proceeds without the loss or gain of water molecules

suggest why the purified crystalline solid is used rather than amphetamine itslef

explain why enzyme reactions speed up as the temperature is increased but stop altogether if the temperature is too high

write an ionic equation, including state symbols for the precipitation reaction that forms a pale blue precipitate

what happens if excess ammonia is shaken with Cu(OH)2

in terms of crystallinity and melting point suggest how the properties of a cis-trans mixed chain polymer differ from the properties of an all trans chain polymer

name a chemical method which chemists can use to produce a polymer with slightly different properties

explain how zwitterions are formed

in living cells only one isomer can act as a substrate for enzymes, explain why

explain why it is important for the pH to be controlled in an enzyme-catalysed reaction

suggest and explain why you would expect he voltage of a cell to be different from a calculated value

describe one property that steel has as a result of containing chromium and nickel

other than recycling materials, what important role does adding scrap steel serve

in the production of steel what elements are removed by direct oxidation with gaseous oxygen?

describe how ninhydrin should be used as a locating agent

what happens to molecules when they absorb infrared radiation

coating steel with zinc prevents rusting in a different way than coating with an organic polymer, explain the differenc

describe some factors that would be investigated in human clinical trials

explain how condensation polymerisation is different from addition polymerisation

describe and explain how the properties of polymers change at low and high temperatures

what is meant by the term heating under reflux?

explain why a compound may have a geometric isomer

what are two methods of measuring H+ concentration

how could you use a graph to show how the rate of reaction varies during the course of the reaction

explain why an enzyme is specific for the reaction it carries out

give the reagent used to convert sodium salts into the corresponding acids

what interactions can hold the tertiary structure of a protein together?

why is chromium classed as a transition metal?

what tests will have to be done before a complex is allowed to be added to bottled drinks?

suggest a method for the disposal of plastic waste and explain the advantage of this method

what are some differences between DNA and RNA molecules?

outline how DNA is able to replicate genetic information

explain how organic nitrogen-containing compounds act as bases

why is it important to add scrap steel?

in a blast furnace apart from oxides and oxygen, what else is lost? what's put in?

a molecule with an asymmetric carbon atom exists as two enantiomers. explain why these are different compounds

explain how molecular formula can be determined from an accurate mass:charge ratio for the M+ peak in its mass spectrum

give three questions that clinical trials are designed to answer

why are carboxylic acids soluble in alkaline solution?

how would you use concentrations of solutions measured at different time intervals to show that the reaction taking place is first order with respect to the compound?

explain why enzyme activity is less when the temperature is higher than the optimum

explain why enzyme activity is less when the pH is changed slightly from its optimum value

explain why at low concentrations of P the reaction is first order with respect to P

explain why at high concentrations of P the reaction is no longer first order with respect to P. what is the new order of the reaction (w.r.t.P)?

give five ways in which enzymes may increase the efficiency of an industrial process

explain the disadvantage associated with the formation of HCl in a condensation reaction

explain why dilute hydrochloric acid will react with zinc

suggest and explain why a student didn't form an aldehyde but a carboxylic acid instead when and primary alcohol was oxidised

describe and explain how an alteration in the sequence of bases can result in enzymes becoming less effective for a particular reaction

explain why phenols are able to dissolve in water if a little aqueous alkali is added to the mixture of phenol and water

explain how transition metal ions such as Cu2+ are able to increase the rate of a redox reaction

describe and explain two methods of protecting copper from corrosion

when determining the rate of reaction w.r.t substance x, why use an excess of other substances?

explain why 1,2-dichloroethene shows E/Z isomerism whereas E300 does not. [E300 has a pentene ring, and two -OH groups attached to the C=C bond in the ring]

describe and explain one difference between heating under reflux and distillation

explain in terms of structure and bonding why amino acids have a high melting point

BrO3- ions can react with Br- in acidic solution to form bromine. Explain why colorimetry can be used to follow this reaction

explain how the orders of reaction support the chemists' suggested rate-determining step

explain, in terms of fixed frequencies of light, why some transition metal ions in solution are coloured

give the meaning of the term crystallinity

suggest one reason why PLA - a polymer made from corn starch is 'greener' than poly(ethene)

suggest a method for removing Fe2O3 from a mixture

give the meaning of the term electronegativity

explain the term tertiary structure

what does the colour that a transition metal absorbs depend on?

explain why a protein with a tertiary structure is affected by pH change

why was a black card placed behind the test tubes?

describe how you would use a rate of reaction vs temperature graph to find the relative rates of reaction at two different temperatures

when the substrate concentration is high state the order of reaction with respect to the substrate. explain your answer

what properties should a solvent have to achieve efficient recrystallization?

explain why phenols react with aqueous sodium hydroxide and suggest why the products are soluble in water

why is it necessary to measure the rate of reaction when the amounts of reactants used up were small in comparison to the total quantities of reactants present?

explain how cross-links are formed

cross-linked poly(acrylic acid) does not dissolve when water is added. Poly(acrylic) acid without cross-links eventually dissolved when sufficient water is added. Suggest and explain a reason for this difference in properties

describe how the student used a colorimeter to find out how the concentration of the blue dye changed when added to the polymer

suggest why scientists once thought that proteins were more likely to transmit genetic data

stronger oxidising agents....