EDEXCEL A LEVEL CHEMISTRY
(PAPER 3) EXAM 2025 QUESTIONS AND
ANSWERS
What can heat help a solid do? - ANS dissolve
why should the volumetric flask be shaken when making a standard solution? - ANS to
ensure a uniform concentration
why is a volumetric pipette more accurate than a measuring cylinder? - ANS smaller
uncertainty
if the burette isn't rinsed with the substance that will be put in it, residual water might have
what effect? - ANS dilute the concentration leading to a larger titre
what is the problem with leaving the funnel in the burette? - ANS small drops of liquid may
fall from the funnel leading to a lower titre volume
why is it okay to rinse with distilled water in a titration? - ANS it doesn't add any extra mols
of reagents
what can you do to decrease apparatus uncertainties? - ANS decrease sensitivity uncertainty
by using a greater resolution or increase the size of the measurement
1 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
, how would you reduce % uncertainty in a burette? - ANS 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? - ANS use a balance that measures
to more decimal places
is water a poor or good nucleophile? - ANS poor
how does water react with halogenoalkanes - ANS slowly in a substitution reaction
why does water go in the liebig condenser from the bottom? - ANS to go against gravity
allowing more efficient cooling and preventing the backflow of water
why should electric heaters be used to heat organic substances? - ANS highly flammable
why should a reflux condenser never be sealed? - ANS build up of gas pressure could cause
explosion
what are anti-bumping granules? - ANS prevent vigorous uneven boiling by making small
bubbles form instead of larger bubbles
general method for purifying an organic liquid - ANS 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 - ANS 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
2 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
(PAPER 3) EXAM 2025 QUESTIONS AND
ANSWERS
What can heat help a solid do? - ANS dissolve
why should the volumetric flask be shaken when making a standard solution? - ANS to
ensure a uniform concentration
why is a volumetric pipette more accurate than a measuring cylinder? - ANS smaller
uncertainty
if the burette isn't rinsed with the substance that will be put in it, residual water might have
what effect? - ANS dilute the concentration leading to a larger titre
what is the problem with leaving the funnel in the burette? - ANS small drops of liquid may
fall from the funnel leading to a lower titre volume
why is it okay to rinse with distilled water in a titration? - ANS it doesn't add any extra mols
of reagents
what can you do to decrease apparatus uncertainties? - ANS decrease sensitivity uncertainty
by using a greater resolution or increase the size of the measurement
1 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
, how would you reduce % uncertainty in a burette? - ANS 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? - ANS use a balance that measures
to more decimal places
is water a poor or good nucleophile? - ANS poor
how does water react with halogenoalkanes - ANS slowly in a substitution reaction
why does water go in the liebig condenser from the bottom? - ANS to go against gravity
allowing more efficient cooling and preventing the backflow of water
why should electric heaters be used to heat organic substances? - ANS highly flammable
why should a reflux condenser never be sealed? - ANS build up of gas pressure could cause
explosion
what are anti-bumping granules? - ANS prevent vigorous uneven boiling by making small
bubbles form instead of larger bubbles
general method for purifying an organic liquid - ANS 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 - ANS 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
2 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
