2741164
| Pregunta | Respuesta |
| what is a primary alcohol? | the carbon atom to which the OH group is attached is in turn attached to one other carbon atom |
| what is a secondary alcohol? | the carbon atom to which the OH group is attached is in turn attached to two other carbon atoms |
| what is a tertiary alcohol? | the carbon atom to which the OH group is attached is in turn attached to three other carbon atoms |
| chemical test to show a substance contains a phenol group | reagent added: iron (III) chloride in neutral solution observation: turns purple |
| what is the molecular ion peak? | the furthest peak on the right |
| describe how you would carry out thin layer chromatography | pencil line near bottom of plate spot small sample of mixture on line solvent in beaker below sample cover beaker with lid leave until solvent front nears top of plate remove and dry plate UV light/iodine to locate |
| catalyst and conditions used to convert carboxylic acid and alcohol into an ester | concentrated sulphuric acid heat under reflux |
| explain the following order of acidity alcohol < phenol < carboxylic acid | acids are proton donors acidity depends on stability of anion formed in solution stability depends on electron delocalisation in the anion order of delocalisation acid > phenol > alcohol so equilibrium lies further to right in acids then phenols |
| why add concentrated sulphuric acid in order to form an ester? | acts as a catalyst moves equilibrium to the right increases rate of reaction |
| why heat under reflux? | prevent loss of volatile products or reactants |
| what do you add to solution to convert a carboxylate salt to its respective acid? | excess sulphuric acid/hydrochloric acid |
| suggest a method of obtaining a pure sample from a mixture | fractional distillation |
| reasons to use a carboxylate salt rather than a carboxylic acid (for medicines) | solids easier to administer taste/smell reduced not acidic not corrosive easier to make sure correct dosage more soluble in water |
| colour change with iron (III) chloride in neutral solution test | yellow to purple |
| key points for vacuum filtration | buchner flask with side arm buchner funnel with filter paper arrow to water pump no leaks in apparatus |
| tests medicines need to undergo to be acceptable as a safe medicine | toxicity trials with animals stability on storage trials with humans to determine side effects tests to determine size of overdose |
| reasons why chemists may want to modify the structure of a molecule | improve effect widen its use reduce side effects improve its properties make it more specific |
| why may chemists want to find synthetic replacements for some natural fibres? | improve properties demand may be greater than nature can supply reduce cost |
| explain the meaning of condensation | two molecules join together and eliminate a molecule of water |
| explain in terms of intermolecular forces of attraction why nylon has a high tensile strength | nylons have hydrogen bonding BETWEEN the chains hydrogen bonding strongest type of IMFA greater energy needed to separate IMFA between the chains |
| advantages of burning to dispose of plastics | no solid waste which is expensive to dispose of no landfill needed energy recycled |
| advantages of burying to dispose of plastics | no gas emissions so doesn't contribute to global warming etc non-biodegradable so no threat to environment |
| conditions for hydrolysis | moderately concentrated sulphuric acid heat under reflux |
| explain the meaning of the term condensation polymer | lots of monomers joined together monomers have reactive groups either end small molecule eliminated e.g. water |
| methods to re-use waste plastics to save natural resources | Sorting out plastics then melting/heating and remoulding Incineration /burning to produce energy/heat Cracking/breaking down chains to produce feedstock Hydrolyse /converting back to monomers and repolymerising |
| how could you determine if a sample of a substance is pure? | determine melting point should be sharp if pure compare to expected value |
| explain why cold drawing increases the tensile strength of a polymer | neck formed so polymer chains more crystalline more points of contact between chains so more opportunities for IMFA more difficult for chains to slide over each other |
| useful properties of Kevlar that arise from its structure | waterproof bulletproof scratch resistant low density rigid (doesn't stretch) doesn't corrode durable can be made into fibres high melting point |
| explain the process of recrystallisation | dissolve the solid in the minimum volume of hot solvent filter and retain the filtrate allow to cool so crystals form wash crystals in minimum volume of cold solvent allow to dry in air or dessicator |
| what feature makes a carbon atom chiral? | four different groups attached to central carbon atom |
| how could you tell from a graph that a reaction is first order with respect to a substrate? | half life constant concentration of substrate never reaches zero (asymptote) |
| what is meant by the primary structure of a protein? | order/sequence in which amino acids are joined together |
| describe the chemical structure off DNA | DNA consists of two(polynucleotide) chains/strands In a double helix Each strand/chain/backbone is made of deoxyribose/sugar and phosphate groups Each chain has attached bases Bases linked by hydrogen bonding Specific/complementary bases are paired/e.g. A-T C-G (between chains) |
| what is meant by the term 'heat under reflux' | reaction mixture heated and vapours cooled liquid returned to mixture no loss of reactants or products |
| what information can be obtained from n.m.r spectra? | type of hydrogen atoms present relative number of each type |
| explain how enzymes can form ionic bonds with substrates | charged groups on side/R groups of substrates can attract charged groups in the active sites of enzymes |
| explain what the term 'coordination number' means | number of dative covalent bonds around central ion |
| explain why [Fe(C2O4)3]3- ions appear green in aqueous solution | d electrons are excited from LFEL to HFEL by radiation in the visible region difference between two energy levels corresponds to visible light complementary colour transmitted (green) |
| outline the steps in performing a titration reaction starting with a weighed sample of lawnsand and a standard solution of aqueous potassium manganate (VII) | Make up to known volume with water Add acid (must be sulphuric if named) Until first permanent pink colour 3 from Filter solution Wash with water Dilute stock solution Pipette sample Add MnO4- from a burette Repeat |
| why can edta4- act as a hexadentate ligand? | 6 lone pairs of electrons so can form 6 dative covalent bonds to central metal ion |
| how would you determine the concentration of ions in a sample using colorimetry? | select a suitable filter zero colorimeter with distilled water prepare solutions of known concentration suitable range measure absorbance of these and record in table plot calibration curve measure absorbance of sample and read off concentration from calibration curve |
| when excess dilute aqueous ammonia is added to Cu(OH)2 what happens? what complex is formed? | precipitates dissolves deep blue solution formed new complex formed - [Cu(NH3)4(H2O)]2+ |
| write an equation to show the reaction of magnesium with sulphur. What type of reaction is this? | Mg + S --> MgS redox reaction |
| what is the problem with having a too high concentration of phosphorous when making steel? | phosphorous concentration too high blow time would need to be longer unsuitable |
| why is it necessary to reduce the percentage of carbon in molten iron in order to make steel? | too much causes the steel to become brittle or difficult to shape |
| what is a problem associated with carbon monoxide? | carbon monoxide is toxic/poisonous |
| write an equation to show the reaction of silicon with oxygen | Si + O2 --> SiO2 |
| write an equation to show the reaction of silicon oxide with calcium oxide to form a slag | SiO2 + CaO --> CaSiO3 |
| explain how painting helps to prevent a car from rusting | prevents oxygen/ air and water getting to steel forms protective barrier between steel and air and water |
| stainless steel contains chromium. suggest how the presence of chromium prevents the formation of rust | chromium reacts with oxygen so is oxidised layer of chromium (III) oxide formed oxide is impermeable to oxygen and water oxide layer quickly reforms if surface scratched stops steel from oxidising |
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