1|Page
EDEXCEL A LEVEL CHEMISTRY (PAPER 3)
COMPREHENSIVE Q&A FOR GUARANTEED
PASS
what are anti-bumping granules? - correct-answer-prevent vigorous uneven
boiling by making small bubbles form instead of larger bubbles
general method for purifying an organic liquid - correct-answer-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
detailed method for preparing and purifying an ester - correct-answer-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
, 2|Page
describe the steps in purifying an organic solid - correct-answer-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
what in an advantage of steam distillation? - correct-answer-the product distills at
a lower temperature which can prevent decomposition
why should wire not be used in the salt bridge? - correct-answer-it will set up its
own electrode system with the ions
components of the SHE - correct-answer-0 volts E, Hydrogen gas at 100kpa, H+
ions at 1moldm3, 298k, pt black catalyst (porous an can absorbs hydrogen gas)
Ecell - correct-answer-Ecell = Erhs-Elhs
why a re high resistance voltmeters used? - correct-answer-to stop the current
from flowing
EDEXCEL A LEVEL CHEMISTRY (PAPER 3)
COMPREHENSIVE Q&A FOR GUARANTEED
PASS
what are anti-bumping granules? - correct-answer-prevent vigorous uneven
boiling by making small bubbles form instead of larger bubbles
general method for purifying an organic liquid - correct-answer-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
detailed method for preparing and purifying an ester - correct-answer-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
, 2|Page
describe the steps in purifying an organic solid - correct-answer-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
what in an advantage of steam distillation? - correct-answer-the product distills at
a lower temperature which can prevent decomposition
why should wire not be used in the salt bridge? - correct-answer-it will set up its
own electrode system with the ions
components of the SHE - correct-answer-0 volts E, Hydrogen gas at 100kpa, H+
ions at 1moldm3, 298k, pt black catalyst (porous an can absorbs hydrogen gas)
Ecell - correct-answer-Ecell = Erhs-Elhs
why a re high resistance voltmeters used? - correct-answer-to stop the current
from flowing
