Practicals Flashcards
Temp changes
- Measure 25cm3 of hydrochloric acid into a polystyrene cup.
- Place the cup inside the beaker to make it more stable.
- Measure and record the temperature of the hydrochloric acid.
- Measure 5cm3 of sodium hydroxide and add it to the polystyrene cup.
- Quickly put a lid on the cup and gently stir the solution with the thermometer through the
hole of lid. - When the reading on the thermometer stops changing and becomes fairly constant,
record the temperature. - Repeat steps 4 and 5 to add further 5 cm3 amounts of sodium hydroxide to the cup. A
minimum total of 40 cm3 needs to be added. - Repeat steps 1–7 to ensure reliability of results.
- Calculate the mean maximum temperature reached for each of the sodium hydroxide
volumes
Rate of reaction (magnesium
- Measure 50 cm3 of 1.0 M hydrochloric acid using one of the measuring cylinders. Pour the acid into the 100 cm3 conical flask.
- Set up the apparatus as shown in one of the diagrams below.
- Add a 3 cm strip of magnesium ribbon to the flask and quickly place the bung back into
the flask. At the same time, start the stopwatch. - Record the volume of hydrogen gas given off every 10 seconds. Stop when no more gas
is given off. - Repeat steps 1-4 using 1.5 M hydrochloric acid
- Plot a graph of ‘volume of gas produced’ (y-axis) against ‘time’ (x-axis) . Draw two
curves, one for each concentration of acid.
Rate of reaction thiosulfate
Measure 10 cm3 sodium thiosulfate solution into the conical flask.
2. Dilute the solution by adding 40 cm3 water into the conical flask making the concentration
8 g/cm3 .
3. Put the conical flask on the black cross.
4. Measure 10 cm3 of dilute hydrochloric acid.
5. Add the acid to the flask. Then quickly at the same time, swirl the flask gently and start
the stopwatch.
6. Look down through the top of the flask. Stop the clock when you can no longer see the
cross and record the time taken.
7. Repeat steps 1‒6 , using different volumes of sodium thiosulfate and water . This will change the concentration of sodium thiosulfate.
8. Repeat steps 1-7 twice more.
9. Calculate the mean time for each of the sodium thiosulfate concentrations.
Chromatography
Measure 10 cm3 sodium thiosulfate solution into the conical flask.
2. Dilute the solution by adding 40 cm3 water into the conical flask making the concentration
8 g/cm3 .
3. Put the conical flask on the black cross.
4. Measure 10 cm3 of dilute hydrochloric acid.
5. Add the acid to the flask. Then quickly at the same time, swirl the flask gently and start
the stopwatch.
6. Look down through the top of the flask. Stop the clock when you can no longer see the
cross and record the time taken.
7. Repeat steps 1‒6 , using different volumes of sodium thiosulfate and water - 20 cm3
sodium thiosulphate solution + 30 cm3 w ater, 30 cm3 s odium thiosulphate solution + 20
cm3 water, 40 cm3 sodium thiosulphate + 10 cm3 w ater). This will change the concentration of sodium thiosulfate.
8. Repeat steps 1-7 twice more.
9. Calculate the mean time for each of the sodium thiosulfate concentrations.
Analysing sediment in water sample
Use universal indicator to test the pH of the water.
2. Measure and record the mass of an empty evaporating basin.
3. Pour 10 cm3 water into the evaporating basin and evaporate the water using a
bunsen burner until the most of the water has evaporated.
4. Once the evaporating basin is cool, reweigh and record the change in mass. 5. Calculate the mass of dissolved solids in the water.
Distillation
- Place the water sample in a conical flask and set up the apparatus for distillation.
- Heat the water gently using a bunsen burner until it boils. Then reduce the heat so the
water boils gently. - Collect around 1 cm depth of water in the cooled test tube, then stop turn the bunsen
burner off. - Analyse the water you have distilled with cobalt chloride paper.
Chromatography correct
Draw a horizontal pencil line 2 cm from the short edge of the chromatography paper.
Mark pencil spots at equal intervals across the line but not too close to the end of the paper.
2. Use a glass capillary tube to put a small spot of each colouring on the pencil spots. A small spot ensures that the colouring separates clearly. Label each spot in pencil.
3. Pour about 1 cm’ of water into the beaker.
4. Suspend the paper in the beaker so that bottom edge of the paper dips into the water.
y. vail or the water sovent to rave at east iree guarters or the way yo the oaber.
Remove the paper and draw another pencil line at on the dry part of the paper right next to the wet edge. This is the solvent front, the distance travelled by the solvent.
6. Hang the paper up to dry thoroughly.
7. Calculate the R, values for each spot. Rf value is calculated by distance travelled by substance/ solvent front.
