Core practical's Flashcards
Chromatography summary method
- Use a ruler to draw a horizontal line 2 cm from a short
edge of the chromatography paper. - Use a glass capillary tube to put a small spot if the
substance on the pencil line. - Pour a small amount of water into the beaker, making
sure it is below the level of the pencil line. - Secure the other end of the chromatography paper to a
splint or glass rod and rest it on the top of the beaker with
the other end just dipped in the solvent. - Wait for the solvent to travel up the paper. Remove the
paper. - Draw another pencil line on the paper at the solvent
front. - Measure the distances travelled by the spots and the
distance travelled by the solvent. - Calculate the Rf value:
Distillation summary method
- Add the solution to a conical flask (this could be ink and
water/salt and water). - Set up the apparatus for distillation (see diagram).
- Place a mixture of ice and water in the beaker
surrounding the test tube. - Heat the solution with a bunsen flame until it starts to
boil. - The solvent will collect in the boiling tube.
Preparing copper sulphate summary method
Copper sulphate is a salt and can be made by reacting the
base copper oxide with sulphuric acid.
1. Measure out 20 cm3 dilute sulphuric acid using a
measuring cylinder and pour into a conical flask.
2. Warm the acid to 50
oC using a water bath.
3. Add a little copper oxide powder and stir.
4. Keep adding copper oxide until it is in excess and no
longer reacts.
Excess copper oxide is used to make sure all the acid has
reacted so you can make a pure salt.
5. Filter the mixture.
This removes the unreacted CuO and leaves just the
copper sulphate and water.
6. Crystalise the salt by reducing the volume in an
evaporating basin over a beaker of water, then leaving to
dry to allow all the water to evaporate.
This produces bigger salt crystals and is safer because the
solution could spit if evaporated to dryness.
Investigating neutralisation summary method
- Measure out 50 cm3 dilute HCl using a measuring
cylinder. Pour into a beaker. - Record the pH of the solution by dipping a glass rod in
the solution and touching this to some universal indicator
paper. Match the colour the appropriate pH on the colour
chart. - Measure out 0.3 g powdered calcium hydroxide.
Add to the beaker and stir.
You can also use powdered calcium oxide. - Record the pH of the solution.
- Repeat the addition of 0.3 g of base 7 times so you add
a total of 2.4g.
Electrolysis of copper sulphate
solution using graphite electrodes summary method
- Set up the circuit as shown in the diagram.
- Turn on the power and observe what happens at each
electrode.
The cathode develops a coating of copper.
HT only: the copper ions in solution gain electrons and
form copper atoms.
Oxygen is formed at the anode.
HT only: hydroxide ions lose electrons to form oxygen and
water.
Electrolysis of copper sulphate
solution using copper electrodes summary method
This method is used to purify copper.
- Select 2 pieces of copper for the anode and cathode.
Weigh each and record the mass of each. - Set the circuit up as shown in the diagram.
- Set the current to about either 0.2A, 0.3A, 0.4A or 0.5A.
- Use the variable resistor to adjust the current and keep
it at the same value throughout the experiment. - Keep the current flowing for 20 minutes.
- Turn off the power and remove the electrodes. Gently
wash them with distilled water, then dip in propanone.
The electrodes are dipped in propanone so they dry more
quickly. Propanone evaporates more easily than water. - Measure and record the masses of the dry electrodes.
- Repeat for al current values.
Acid-alkali titration summary method
- Rinse the burette with acid, then fill with acid. Record the initial volume.
- Measure out 25cm3 alkali with a volumetric pipette and empty into a conical flask.
- Add a few drops of indicator to the alkali and place on a white tile under the burette.
- Add the acid to the alkali, swirling the flask.
- When the indicator starts to change colour, rinse the tip of the burette and the sides of the flask with distilled water to ensure all the acid is in the alkali. Continue adding acid drop by drop until the indicator has changed colour and the end point reached. You have to know the colour changes of the indicators. You cannot use UI because it does not have a single, clear colour change.
- Record the final volume of acid in the burette.
- Repeat until concordant results are obtained.
Investigating reaction rates -
measuring gas volume summary method
This method is to investigate the effect of changing the
surface area of marble chips in the reaction with HCl.
They could ask for any variable or any chemical reaction
that gives off a gas.
1. Set up the apparatus as shown in the diagram, either
with the gas syringe or collection over water.
2. Measure out the HCl into a conical flask.
3. Add a known mass (about 5g) of large marble chips
(calcium carbonate) to the flask.
4. Immediately stopper the flask and start the stop clock.
5. Record the volume of gas produced every 30 s until the
reaction has finished.
6. Repeat for the same mass of small marble chips.
Investigating reaction rates -
observing a colour change summary method
This investigation was looking into the effect of
temperature on the rate of reaction between sodium
thiosulphate and HCl. The reaction makes a cloudy yellow
precipitate. The effect of concentration could also be
investigated. Other colour change reactions could be
used.
1. Measure out the sodium thiosulphate solution and pour
into a conical flask. Measure out the HCl and pour into a
test tube.
2. Put both solutions into a water bath at the desired
temperature.
3. When at temperature, remove the flask and place on a
cross on a piece of paper. Add the HCl and start the stop
clock.
4. Stop the cock when the cross disappears.
5. Repeat for other temperatures.
The combustion of alcohols summary method
- Measure out 100g of water in the copper calorimeter.
Measure and record the temperature of the water. - Weigh the spirit burner and record the mass.
- Place the spirit burner under the can and light.
- Stir the water and heat until the water temperature has
increased by about 20
oC. - Extinguish the flame using the lid.
- Measure and record the highest temperature reached
by the water. - Measure and record the mass of the burner again.
- Calculate the temperature rise and the mass of fuel
burnt. - Calculate the energy supplied to the water, then divide
this by the mass of fuel burnt to give an energy value per gram of fuel.
They will give the formula to calculate the energy supplied.
Identifying ions - flame tests summary method
- Clean the nichrome wire in acid, then put in the flame.
- Dip into the solid compound, or solution.
- Hold the wire in the flame and note the colour.
Lithium=red, Sodium=yellow, Potassium=lilac, Calcium=orange-red, Copper=blue-green.
Identifying ions - hydroxide precipitate test summary method
- Use the solution or dissolve a little of the solid in some
water. - Add a few drops of sodium hydroxide solution. Record
the colour of the precipitate. - If a white precipitate forms, add excess NaOH and see
if it dissolves.
Aluminium= white, disappears on adding excess, Iron 2+=green, Iron 3+ brown, Copper=blue, Calcium=white.
Identifying ions - ammonium ions summary method
- Dissolve the solid in some water, add dilute NaOH and
warm. - Hold a piece of damp red litmus over the mouth of the
test tube. The litmus will turn blue.
Identifying ions - carbonate test summary method
- Pour a small volume of a sodium solution in a test tube.
- Place some limewater in another test tube.
- Add a set volume of dilute hydrochloric acid to each sodium salt in turn.
- Only if you see bubbles, transfer the gas produced to the limewater.
The limewater turns cloudy in the presence of carbon dioxide
Identifying ions - sulphate test summary method
- Pour a small volume of a sodium solution in a test tube.
- Add drops of dilute nitric acid to each solution. Then add 1cm depth of barium nitrate solution.
A white precipitate of barium sulphate forms if sulphate ions are present
