AQA A-LEVEL CHEMISTRY: RP1, VOLUMETRIC SOLUTION + ACID/BASE
TITRATION: LATEST EXAMINATION QUESTIONS WITH GRADED A+ ANSWERS
METHOD for making volumetric 1. Weigh sample bottle containing solid on 2dp balance.
solution. 2. Transfer solid to beaker and reweigh sample bottle.
3. Record difference in mass to find mass of solid.
4. Add distilled water, stir with glass rod until all solid dissolves.
5. Transfer to volumetric flask with washings.
6. Make up to 250cm^3 with distilled water.
7. Invert flask ten times to mix content.
ERRORS for making volumetric solution. 1. Ensure solid isn't too old or it would have picked up
water > affecting mass values.
2. Fill so bottom of meniscus sits on line on the flask neck.
Put paper behind to help you see.
HOW TO REDUCE UNCERTAINTIES for 1. Usemore accurate mass balance or large mass.
making 2. Weighing by difference ensure more accurately recorded mass.
volumetric solution.
METHOD for acid/base titration. 1. Pour 100cm^3 of std solution of known conc into beaker (acid).
2. Fill burette with std solution of known conc.
3. Pour 100cm^3 of solution with unknown conc into 2nd beaker
(alkali).
4. Use pipette filler to transfer 25cm^3 of solution into a
250cm^3 conical flask.
5. Add 2/3 drops of indicator (phenolpthalein) to conical
flask sol, noting initial colour.
6. Record initial burette reading.
7. Titrate contents by adding sol from burette until sharp
colour change observed. Record final burette reading and
calculate titre vol (change in burette vol).
8. Repeat until 2 CONCORDANT results obtained. Have at
least one trial and typically 3 titrations done in total.
TITRATION: LATEST EXAMINATION QUESTIONS WITH GRADED A+ ANSWERS
METHOD for making volumetric 1. Weigh sample bottle containing solid on 2dp balance.
solution. 2. Transfer solid to beaker and reweigh sample bottle.
3. Record difference in mass to find mass of solid.
4. Add distilled water, stir with glass rod until all solid dissolves.
5. Transfer to volumetric flask with washings.
6. Make up to 250cm^3 with distilled water.
7. Invert flask ten times to mix content.
ERRORS for making volumetric solution. 1. Ensure solid isn't too old or it would have picked up
water > affecting mass values.
2. Fill so bottom of meniscus sits on line on the flask neck.
Put paper behind to help you see.
HOW TO REDUCE UNCERTAINTIES for 1. Usemore accurate mass balance or large mass.
making 2. Weighing by difference ensure more accurately recorded mass.
volumetric solution.
METHOD for acid/base titration. 1. Pour 100cm^3 of std solution of known conc into beaker (acid).
2. Fill burette with std solution of known conc.
3. Pour 100cm^3 of solution with unknown conc into 2nd beaker
(alkali).
4. Use pipette filler to transfer 25cm^3 of solution into a
250cm^3 conical flask.
5. Add 2/3 drops of indicator (phenolpthalein) to conical
flask sol, noting initial colour.
6. Record initial burette reading.
7. Titrate contents by adding sol from burette until sharp
colour change observed. Record final burette reading and
calculate titre vol (change in burette vol).
8. Repeat until 2 CONCORDANT results obtained. Have at
least one trial and typically 3 titrations done in total.
