Edexcel A Level Chemistry (Paper 3)

Edexcel A Level Chemistry (Paper 3) AgBr + conc NH3 - complex ion AgCl + dilute NH3 - complex ion ammonium test - react with warm NaOH to get NH3 components of the SHE - 0 volts E, Hydrogen gas at 100kpa, H+ ions at 1moldm3, 298k, pt black catalyst (porous an can absorbs hydrogen gas) describe the steps in purifying an organic solid - dissolve the impure compound in a minimum vol of hot solvent, hot filter solution to remove any insoluble impurities, cool the filtered solution by inserting the beaker in ice, use buchner filtration to separate out crystals, wash the crystals with distilled water to remove soluble impurities, dry crystals between filter paper detailed method for preparing and purifying an ester - mix primary alcohol and carb acid, add conc sulphuric acid drop by drop (to prevent uncontrolled boiling) and cool in a water bath, when all acid has been added fit a reflux condenser to the flask and gently heat the mixture over an electric heating mantle, cool mixture and re-arrange apparatus for distillation, shake distillate in separating funnel with NaCO3 soln releasing the pressure at intervals, the lower aq layer is discarded, the crude ester is shaken in a separating funnel with CaCl soln removing any unreacted alcohol then discard the lower layer, the ester is run into a clean dry flask with anhydrous cacl, the ester is filtered into a clean dry flask with some anti-bumping granules and distilled disadvantages of fuel cells - expensive, transporting pressurised liquid, limited lifetime, use of toxic chemicals in production Ecell - Ecell = Erhs-Elhs general method for purifying an organic liquid - put distillate of impure product into a separating funnel, was by adding saturated NaCl, allow layers to separate then run off the aq layer, run the organic layer into a dry conical flask and add drying agent (eg anhydrous calcium chloride), carefully decant the liquid into the distillation flask, distill to collect pure product how can hydrogen be stored in fuel cells? - liquid under pressure, adsorbed onto a solid surface, absorbed within a solid material how does water react with halogenoalkanes - slowly in a substitution reaction how would you reduce % uncertainty in a burette? - make the titre a larger volume by increasing conc and vol of the substance in the conical flask or decreasing the conc of the substance in the burette how would you reduce % uncertainty in measuring mass? - use a balance that measures to more decimal places if the burette isn't rinsed with the substance that will be put in it, residual water might have what effect? - dilute the concentration leading to a larger titre is water a poor or good nucleophile? - poor Silver Iodide + Ammonia Solution - no rection sulphates test - BaCl2 gives a white ppt test for carbon dioxide/ CO3^2-/HCO3- - dilute acid gives effervescence, limewater colourless to cloudy test for halide ions - AgNO3 and nitric acid transition metal colour arises from... - electronic transitions from ground to excited states between d-orbitals a quanta of visible light is adsorbed to promote electrons to higher energy levels, the light is absorbed and the opposite colour is transmitted uncertainties - burette is 0.05, pipette is 0.1, balance is 0.001 v2+ - +2, violet v3+ - +3, green vo+ - +5, yellow vo2+ - +4, blue what are anti-bumping granules? - prevent vigorous uneven boiling by making small bubbles form instead of larger bubbles what can heat help a solid do? - dissolve what can you do to decrease apparatus uncertainties? - decrease sensitivity uncertainty by using a greater resolution or increase the size of