809486
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Fichas por joannalivesey, actualizado hace más de 1 año
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Creado por joannalivesey
hace más de 10 años
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| Pregunta | Respuesta |
| Rates of reaction were measured when the amounts of reactants used up were small compared to total quantities of reactants present. why? | • rate measured will be for the initial concentrations • As reactants are used up, the rate will decrease |
| Why can -NH2 act as a base? | • NH2 group has a lone pair of electrons • which can accept a proton |
| Effect of a DNA mutation on enzymes | • Enzymes are proteins with a specific sequence of amino acids • mutation changes DNA base sequence which means primary structure is changed • therefore tertiary structure also changes • the active site is where the reaction with the substrate takes place • an altered active site will not have the correct shape and so substrate cannot bind |
| What properties do chromium and nickel give steel? | • Resistance to corrosion • High strength |
| what is meant by zero order? | • concentration of X does not alter the rate of reaction |
| Measuring initial rate on a time-conc graph | • measure gradient by drawing tangent at time = 0 • gradient of tangent gives rate of reaction |
| Why does alloying increase strength of metal? | • Different sized atoms • Makes lattice less regular • Layers of atoms prevented from slipping |
| Explain what is meant by the term complex ion | • Central metal ion surrounded by ligands • ligands donate a lone pair of electrons to form dative covalent bonds |
| Why are complexes coloured? (long answer) | • Ligands cause splitting of d sub shell into two energy levels • The d orbitals are partially filled • Electron is excited from lower energy level to higher energy level • Specific frequencies of visible light are absorbed (delta E=hv) • Complementary colour is transmitted, and is the colour that we see |
| Describe the structure of DNA | • DNA consists of two polynucleotide chains in a double helix • each nucleotide is made up of deoxyribosem, a phosphate group and an nitrogenous base • the bases on each chain are linked by H bonding • specific bases are paired between the two chains ie A-T, C-G |
| why do enzymes only catalyse specific reactions? | • Enzymes have active sites with a specific shape • substrate can fit into active site to form an enzyme-substrate complex • substrate molecules of a different shape do not fit |
| What is substrate order of reaction at high substrate concentrations? | • Zero • so all the active sites are filled • Therefore the rate depends on how fast enzymes-substrate complex breaks down |
| what makes a carbon chiral? | bonded to 4 different groups |
| what and why is the coordination number of edta4- ? | • six • It has 6 lone pairs with which it forms six dative covalent bonds |
| why should we recycle steel? | • Iron is a non renewable resource • Saves energy and extraction costs • saves landfill space/ mining damage to environment |
| how can enzymes form ionic bonds with substrates? | •NH3+ and COO- groups on enzyme's active site • can attract oppositely charged groups on the substrate |
| how do you determine if a sample is pure? | • sharp melting point • carry out TLC- only one spot |
| Why do molecules absorb infrared radiation at specific frequencies? | energy levels are quantised |
| why is carboxylic acid more acidic than an alcohol? | • H+ can be lost by -OH on the acid/alcohol forming an anion • acidity depends on stability of anion • equilibrium position further to right for carb acid as negative charge can delocalise more across several atoms |
| why do amino acids have such high melting points? | • they form zwitterions which attract each other very strongly due to strong ionic bonds • high energy required to separate particles |
| how can high resolution mass spectrometry be used to find the molecular formula of a compound by using m/z of M+ peak? | • masses are measured relative to carbon-12 (12.00000) • compounds with the same whole number molecular mass will have different Mr values from high resolution spectra • compare Mr with database values |
| what is Fe2O3.xH2O called? | iron (III) hydroxide |
| Why are carboxylic acids soluble in NaOH (aq)? | COOH reacts with NaOH to form a soluble salt |
| effect of pH on enzymes | • change of pH affects charges on polar groups in the active site • e.g. COOH becomes COO- • prevents correct interactions between enzyme and substrate |
| good things about enzymes | • speeds up reaction rate • reduces the number of steps in a synthesis (often one-step) so improves the atom economy • reduces the amount of energy required • easier separation methods • enzymes can be reused/recycled • work well in aqueous environments so fewer organic solvents used (so less hazardous waste) • reduces use of more toxic catalysts |
| what is meant by crystalline? | polymer chains are highly aligned |
| how can you tell if something is in acid-base equilibrium? | transfer of proton (a proton is donated and accepted) |
| what is meant by tertiary structure? | the overall folding of the polypeptide to give the three dimensional shape of the protein |
| how can enzymes catalyse the breakdown of substrates? | • Reaction takes place at enzymes specific shaped active site • interactions between substrate and active site weaken bonds in substrate • activation energy is lowered |
| why do enzymes have an optimum temp? | • high temperatures cause H bonds to break and active site is lost • at low temperatures rate is slow since activation energy is not often reached |
| affect of temps lower than Tg | • polymer becomes brittle • chains do not have enough energy to slide over one another • force applied to change shape of polymer will cause ‘frozen’ chains to break |
| how to calculate Rf? | distance moved by spot ÷ distance moved by solvent front |
| why, after 50 years, are scientists still using Watson and Crick’s model for DNA? | • It explains all the known facts about DNA • it helps predict reactions which can be tested and shown to be correct |
| when talking about what IMFs are present say... | the strongest IMF in x is ..... NOT x has .... |
| why did they originally think proteins held the genetic code? | • there are 20 amino acids in proteins and only 4 bases in DNA • so more combinations in proteins to carry genetic data |
| why don't you need to use an indicator in MnO4 titrations? | only MnO4–(aq) is coloured OR a colour change takes place during the reaction |
| what is a zwitterion? | contains a positive charge and a negative charge |
| what get "zwittered" when zwitterions form? | NH2 and COOH |
| should you write orders as number or letters? | numbers!!! 123432534321 |
| what does mass spec stand for? | mass SPECTROMETRY |
| questions about rds? start with ... | rds depends upon the species given in the rate equation |
| what is meant by the term pharmacophore | the part of the molecule that... • binds to a receptor/active site • is responsible for the pharmacological action |
| competitive inhibition | • inhibitor bonds to active site of enzyme • blocking active site • substrate cannot bond |
| sequence of events from a natural substance to medical drug | • show that a compound has medicinal properties • work out structure and identify pharmacophore • synthesise similar molecules • clinical trials |
| problems with HNO3 + NH3 -> NH4NO3 | • ammonia is toxic • nitric acid is corrosive and toxic • ammonium nitrate is explosive |
| when talking about changes in entropy say... | more negative/positive, instead of lower/higher |
| ways to decrease CO2 levels | • increase photosynthesis (plant more trees) • capture and storage in the oceans/under the sea • capture and storage in former oil wells/porous rock |
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