practicals

measure 100cm3 of water in beaker weigh a spirit burner contiaining liquid to be burnt measure initial temp of water using thermometer use spirit burner to heat water stop heating after a reasonable temp rise, stir and measure final temp of water reweigh spirit burner calculate temp change and heat energy change using q = mcΔt calculate the mass of fuel burnt by subtraction and find number of moles of fuel using mass/Mr calculate enthalpy change per mole of fuel used

heat loss to surroundings from spirit burner and calorimeter loss of fuel from burner or water by evaporation some heat used to raise temp of calorimeter reaction unlikely to occur under standard conditions

using draught shield to reduce heat loss add lid on calorimeter minimise distance between flame and calorimeter insulating calorimeter/spirit burner burn in supply of pure oxgen to minimise incomplete combustion

place polysstyrene cup in glass beaker rinse measuring cylinder with 1 moldm-3 acid then measure 25cm3 and transfer to polystyrene cup stir acid with themometer and record temp rinse second measuring cylinder with 1 moldm-3 base and measure 25cm3 add base to acid and record highest temo reached calculate temp change and heat energy change using q=mcΔt calculate the amount of acid used, the moles of water formed and the enthalpy of neutralisation

dissolve compound in water to form aqueous solution add a few drop of NaOH (aq) at first then excess NaOH positive result = white ppt forms

warm with solid ammonium salt and test gas formed with red litmus paper or glass rod dipped in conc HCl(aq) pungent ammonia gas released which changes red litmus paper to blue (as ammonia gas is alkaline) or produce white fumes with conc HCl reaction : OH- + NH4+ → NH3 + H2O

reagent = acidified barium chloride solution white ppt forms

add dilute HNO3 test gas with limewater effervesence and turns colourless limewater cloudy

organic compounds contain strong covalent bonds so organic reactions are slow reflux increases the rate of reaction

the reaction is often exothermic so this prevents temp of reaction mixture from rising too rapidly and dangerously splashing and forming unwanted side-products

prevents vapour from escaping so the reactants can be boiled for long time without any loss of vapour

ensure smooth boiling because liquid can splash over into the condesnor causing impure product or can cause an explosion

lack of H atom bonded to the C with the OH group attached

warm with ethanol and add a few drops of conc sulphuric acid and smell mixture sweet smell if ester present

sodium carbonate or Mg to test form phenol as not acidic enough to react with carbonates effervescence and turns colourless limewater cloudy effervescence - pop is heard when lighted splin is applied to gas produced (Hydrogen gas formed with Mg )

contamination occurs due to byproducts or unreacted reactant solvent extraction used to purify product: stopper and shake organic liquid with an aqueous solution (usually sodium hydrogen carbonate) impurities more soluble in aqueous solution than in organic liquid so move into the aq sol organic liquid and aq sol are immiscible so form separate layers remove stopper and open tap to run off bottom layer into beaker close tap partially when bottom layer nearly drained to slow down flow open tap again and run off second layer into second beaker discard aqueous solution repeat process using a new sample of aqueous sol