Required Practicals Flashcards
Determination of the composition of copper (II) carbonate
- Set up the apparatus as shown in the diagram (https://i.imgur.com/WEupgMl.png) using a 250cm^3 measuring cylinder and a
250cm^3 conical flask. - Weigh 1.5 g of CuCO3.Cu(OH)2 and add it to the conical flask.
- Measure 50cm3 of H2SO4 into a measuring cylinder.
- Add the H2SO4 into the conical flask and immediately insert the stopper. The gas will collect
in the measuring cylinder. - Record the final volume of carbon dioxide in the measuring cylinder.
- Calculate the amount of carbon dioxide collected.
Determination of the concentration of hydrochloric acid
- Make a 0.10 dmmol^-3 standard solution of sodium hydrogencarbonate
- Use a pipette and pipette filler to transfer 25 cm3 of the standard NaHCO3 solution to a 250
cm3 conical flask. - Add two or three drops of methyl orange to the flask.
- Fill the burette with hydrochloric acid (ensuring there is no air bubble) and record the initial
burette reading - Add the hydrochloric acid from the burette to the conical flask until the end point is reached.
At the end point, the solution will be orange in colour. - Record the final burette reading. The volume of HCl added is the difference between the
initial and final readings. - Repeat until two concordant results are obtained.
Determination of the enthalpy change of neutralisation
- Measure 25 cm^3 1 molar hydrochloric acid using a measuring cylinder and add it to a polystyrene
cup. (https://i.imgur.com/xHqwsg1.png) - Place the cup in a 250 cm^3 glass beaker.
- Construct a suitable table to record the temperature of the acid at minute intervals for up to
10 minutes - Measure 25 cm^3 of 1 molar sodium hydroxide into a measuring cylinder.
- Start the timer and record the initial temperature of the hydrochloric acid in the cup.
- Continue to record the temperature each minute for three minutes.
- At the fourth minute, add the sodium hydroxide to the cup. Do not record the temperature.
- At the fifth minute, continue recording the temperature up until 10 minutes. Stir the solution
in the cup each time the temperature is recorded. - Use the data to work out the T value in q = mcT
Identifying the negative ions (anions) present in mixture A
- Add 25 cm^3 of distilled water into a 100 cm^3 beaker.
- Add mixture A into the water and stir with a glass rod, until most of the solid has dissolved.
- Filter the mixture into a conical flask.
- Add about 2 cm^3 of the filtrate to a test tube.
- Add 5 drops of HNO3 followed by 10 drops of AgNO3 to the test tube. Record any
observations. - To the same test tube, add NH3 dropwise until there is no further colour change. Record any
observations. - Add 1 spatula of the residue from step 3 to a test tube. Add about 2 cm3 of HNO3 to this test
tube. Continue adding HNO3 dropwise until there is no further reaction. Record any
observations. - Add about 2 cm3 of the filtrate from part 1, step 3 to a test tube. Add about 2 cm3 of sulfuric
acid to this test tube and record any observations. - In a new test tube, add 2 cm3 of the filtrate from part 1, step 3 followed by about 2 cm3 of
K2CrO4. Record any observation - Check if your observations match the standard observations for common ions
Synthesis of a liquid haloalkane
- Pour about 6.5 cm3 of 2-methylpropan-2-ol into a 50 cm3 separating funnel and calculate the mass of 2-methylpropan-2-ol used
- Measure 20 cm3 of concentrated hydrochloric acid and gradually add the acid to the
separating funnel. - Place the stopper on the separating funnel and shake it vigorously for 20 minutes, releasing
the pressure when required. - Allow the mixture to separate. Once separated, remove the stopper and open the tap to collect the bottom aqueous layer.
- Weigh an empty sample tube.
- Set up the apparatus as shown in the
diagram. (https://i.imgur.com/bQ7D7xk.png) - Add the organic sample from the conical
flask to the round bottom flask and add
some anti bumping granules. - Collect the liquid impurities that come
through the condenser below 48°C in a
small beaker. - When the temperature reaches 48℃, collect the
liquid from the condenser in the weighted sample tube until no more liquid comes through
the condenser. - Weigh the sample tube and calculate the mass of the product.
7A: Identification of an alkene
Chemicals provided for the experiment ● Heptane ● Cyclohexane ● Cyclohexene ● Limonene ● Bromine water
- For each of the organic substances, in a separate test tube
- Add 10 drops of bromine water to 1 drop of the substance.
- Mix the contents of the test tube thoroughly.
- Record any observations.
Heptane: orange, cyclohexane: top layer orange and bottom layer water, others: colourless
7B: Identification of a haloalkane
Chemicals provided for the experiment: ● 1- chlorobutane ● 1- bromobutane ● 1 -iodobutane ● Ethanol ● Aqueous silver nitrate
- Set up a water bath in a beaker.
- Heat each haloalkane separately under reflux with sodium hydroxide to release the halide
ions. - For each of the haloalkane, in a separate test tube:
- Add five drops of the refluxed haloalkane
- Add 1 cm3 of both ethanol and silver nitrate solution to the test tube.
- Mix the solution well and place the test tube into the water bath.
- Record any observations after 3 minutes.
7C: Identification of Aldehydes
Chemicals provided for the experiment: ● Fehling’s solution ● Tollens’ reagent ● Brady’s reagent ● Ethanal ● Propanone
- In separate test tubes, heat propanone and ethanal with Fehling’s reagent. Make a note of
any observations. - In separate test tubes, heat propanone and ethanal with Tollens’ reagent. Record any
observations. - In separate test tubes, add Brady’s reagent to propanone and ethanal. Note any
observations.
https://i.imgur.com/j8UeRo1.png
7D: Identification of Alcohols
Chemicals provided for the experiment:
● Butan-1-ol ● Butan-2-ol ● 2-methyl-propan-2-ol ● Phenol ● Acidified potassium dichromate solution ● Bromine water
- Heat the butan-1-ol under reflux with the acidified potassium dichromate and make a note
of any observations. - Repeat for butan-2-ol and 2-methyl-propan-2-ol.
- Add bromine water to a sample of phenol and note any changes
(https://i.imgur.com/EKqiPHQ.png)
7E: Identification of Carboxylic Acids
Chemicals provided for the experiment:
● Ethanoic acid
● Dilute sodium carbonate solution
● Limewater
- Add some sodium carbonate solution to the sample being tested.
- Bubble the gaseous product through limewater using a bung and delivery tube.
The ethanoic acid reacts with the sodium hydroxide producing carbon dioxide. Effervescence will
be observed. CO2 turns limewater cloudy
Making an electrochemical cell
- Clean a piece of copper and a piece of carbon using emery paper or fine grade sandpaper.
Rinse the copper and carbon with distilled water then dry them. - Place the copper into a 100 cm3 beaker with about 50 cm3 of 0.1 mol dm-3 CuSO4 solution.
- Using a crocodile clip, connect the copper electrode to the negative terminal of the voltmeter.
- Place the carbon electrode into a beaker containing about 50cm3 of a mixture of aqueous
ammonium iron (II) sulfate: iron (III) chloride (1:5 ratio). - Using a crocodile clip, connect the carbon electrode to the positive terminal of the
voltmeter. - Make a salt bridge by soaking a piece of filter paper in saturated potassium nitrate solution.
Place the ends of the filter paper into the solutions in the beakers. - Measure and record the voltmeter readings in a suitable format.
Clean electrodes with sandpaper
Place into solutions (100cm^3 beaker, 50cm^3 of 0.1mol)
Connect to voltmeter
Make salt bridge
Usually copper in CuSO4, carbon in 1:5 Ammonium iron(II) sulfate to iron(III) chloride
Rate of reaction between magnesium and hydrochloric acid
Method
1. Assemble the apparatus as shown in the picture above (https://i.imgur.com/74aBEEV.png)
2. Add 50cm3 of HCl to the conical flask add a 6cm strip of magnesium to the conical flask and
immediately insert the bung. Start the timer.
3. Record the volume of gas at 15 second time intervals for 2.5 minutes.
4. Repeat for different concentrations of HCl as advised by your teacher.
Analysis
1. For each HCl concentration: Plot a graph of time (sec) on the X-axis against volume of H2
gas produced (cm3) on Y-axis.
2. Draw a line of best fit for your time-points on graph.
3. Draw a tangent at time = 0 and use the gradient to find the initial rate for each
concentration of HCl.
Determination of enthalpy changes of combustion
- Accurately measure 100 cm^3 of water into a calorimeter/beaker.
- Accurately weigh a spirit-burner containing one of the alcohols.
- Arrange the apparatus in such a way that the spirit-burner can be used to heat the water in the
calorimeter/beaker. - Take the temperature of the water before you start heating.
- Use your spirit-burner to heat the water. Stop heating when you have heated the water enough to give a
reasonable temperature rise (15°C). Stir the water thoroughly and measure the final temperature of the
water. - Reweigh the spirit-burner.
Determination of a enthalpy change of reaction by Hess’ Law
- Measure 30 cm^3 (an excess) of 2.00 mol dm^3 hydrochloric acid into a polystyrene cup and place inside a 250 cm^3 beaker.
- Accurately weigh a sample bottle containing between 2.5g and 3.0g of potassium carbonate, K2 CO3 .
- Measure the temperature of the acid and record this value.
- Carefully add the K2CO3 to the acid. Continually stir the mixture, measure the highest or lowest
temperature and record this value. - Reweigh the sample bottle and record this value.
- From your results, calculate the heat absorbed or evolved by the solution.
- Repeat the first experiment using between 3.2g and 3.7g of KHCO3 instead of K2CO3.
- Calculate the amount, in mol, of KHCO3 that reacted and determine the enthalpy change of reaction for the equation above.
Investigating iron tablets
- Grind 5 iron tablets into a powder
- Use a weighing boat to determine the mass of the tablets
- Put the iron tablets in a 100cm^3 conical flask
- Add 50cm^3 sulfuric acid and stopper the flask
- Shake the flask until the solution dissolves
- When the residue settles, filter the solution into a volumetric flask
- Add the washings from the filter paper to the volumetric flask
- Fill the volumetric flask with sulfuric acid up to the mark, to create an acidified solution of iron(II) sulfate
- Fill a burette with potassium permanganate solution
- Pipette 25cm^3 of the acidified solution with 25cm^3 sulfuric acid into the 250cm^3 flask
- Titrate until the solution turns light pink permanently
The equation is 5Fe(2+) + MnO4(-) + 8H(+) => 5Fe(3+) + Mn(2+) + 4H2O
Tablets in 50cm^3 sulfuric acid in flask
Shake and filter solution into vol. flask
Add washings to vol. flask
Fill vol. flask with sulfuric acid
Titrate 25cm^3 of this + 25cm^3 sulfuric acid in a 250cm^3 flask against potassium permanganate until light pink
Preparation of benzoic acid by alkaline hydrolysis of an ester
Add sequentially to a round-bottom or pear-shaped flask (100 cm^3): 2.0 cm^3 of methyl benzoate 10.0 cm^3 of 2.0 molar NaOH 10.0 cm^3 of ethanol A few anti-bumping granules
Fit the condenser to the flask in preparation to heat the mixture under reflux
Heat the flask gently, without allowing the contents to boil, for about 5 minutes, followed by gentle boiling under reflux for a further 15 minutes.
Allow the contents of the flask to cool. Remove the condenser and decant the solution from the anti-
bumping granules into a beaker.
Rinse the flask with distilled water, adding the rinsing solution into the beaker.
Add ten drops of methyl orange indicator to your solution and then acidify with 2.0 molar HCl. Solid benzoic acid will crystallise.
Filter the mixture using Buchner to obtain impure benzoic acid, washing the crystals with ice cold distilled/deionized water.
Recrystallise the impure benzoic acid (see “Recrystallisation of an organic solid”)
Measure the melting point of the pure crystals (see “Melting point analysis”)
Summary: in 100cm^3 RB add 2.0 methyl benzoate, 10 ethanol, 10 2 molar NaOH, and bumping granules
Heat gently without boiling for 5, then reflux for 15. Cool, decant into beaker along with washings. Add ten drops of methyl orange and acidify with 2 molar HCl. Filter using Buchner to obtain impure benzoic acid, then wash, recrystallise and measure the melting point
[OAC3] Recrystallisation of an organic solid
Heat 10cm^3 of solvent to 60 degrees
Dissolve impure compound in minimum hot solvent
Filter hot solution to remove insoluble impurities
Leave filtrate to cool
Pour filtrate into Buchner funnel with moistened filter paper. The Buchner funnel should be connected to a Buchner flask
Turn on the vacuum and let the filtrate be sucked through the filter
Wash the crystals with distilled water
Leave the vacuum on for several minutes to dry the crystals
[OAC3] Thin layer chromatography
Draw a line in pencil about 1 cm from the bottom of the TLC plate. Mark three equally spaced crosses along the line, to indicate the starting positions of the samples.
Use a capillary tube to spot the 3 chemicals on the TLC plate. Each spot should be as small as possible and the spot should be left to dry before the sample is spotted again on top.
Add about 10 cm^3 of solvent into a 100 cm^3 beaker and cover with a watch glass. The watch glass will prevent evaporation of the solvent.
Place the TLC plate into the beaker, making sure that the level of the solvent is below the pencil line. Make sure the watch glass is placed on top of the beaker.
When the solvent is about 1 cm from the top of the plate, remove the TLC plate and mark the solvent front with a pencil. Leave the plate to dry in a fume cupboard.
Place the plate in a beaker with iodine crystals and cover with a watch glass. Once the spots become visible mark them lightly with pencil.
Summary: Draw pencil line and crosses on plate, spot chemicals on plate, leave to dry and add 10 solvent to 100 beaker and cover with watch glass. Place plate in beaker and remove when solvent is 1cm from top. Mark solvent front, dry and use iodine crystals to make chemical visible
Calculate the Rf values of the observed spots.
[OAC3] Melting point analysis
Seal the end of a melting point tube by rotating it in a Bunsen flame, then leave to cool
Place a small amount of the crystals on a watchglass
Fill the tube with the crystals to a depth of 5mm, and then tap the tube to the solid falls down to the sealed end
Use the melting point apparatus to slowly heat the benzoic acid until it melts
Note the range over which the solid melted
Making methyl 3-nitrobenzoate from methyl 3-benzoate
Pipette 2.5cm^3 M3B into a small conical flask and mix it with 5cm^3 concentrated sulfuric acid
Cool the mixture in a 250cm^3 beaker ice/water bath
Add 2cm^3 concentrated H2SO4 to 2cm^3 concentrated HNO3 to a test tube and cool in a 75cm^3 ice/water bath
Add the nitrating mixture to the first mixture drop by drop
Stir the mixture with a small thermometer and keep the temperature below 10 degrees. Allow the mixture to stand at room temperature for 15 minutes
Pour ice into the conical flask and stir until it has melted and precipitation is complete
Filter the mixture using Buchner to obtain impure M3NB, washing the crystals with ice cold distilled/deionized water.
Recrystallise (see “Recrystallisation of an organic solid”)
Complete oxidation of ethanol to a carboxylic acid
Add 4.0 g Na2Cr2O7 to a round-bottomed flask
Slowly add 20cm^3 3 molar sulfuric acid to the flask, then add a few anti-bumping granules
Swirl the flask in an ice water bath for 2-3 minutes until it’s below 10 degrees
Add 0.5cm^3 ethanol to the flask dropwise while swirling in the ice water. You will observe a temperature increase
When the maximum temperature has been reached, repeat these steps again with another 0.5cm^3 ethanol
Clamp the flask, put it into the heating mantle and arrange a condenser above the flask.
Turn on the heat and water flow, and heat under reflux for 20 minutes
Dry the outside of the flask with a paper towel
Heat using a Bunsen flame (see diagram) until you have distilled off 2-3cm^3 of distillate
Complete oxidation of ethanol to an aldehyde
Add 2.0 g Na2Cr2O7 to a round-bottomed flask
Slowly add 20cm^3 2 molar sulfuric acid to the flask, then add a few anti-bumping granules
Swirl the flask in an ice water bath for 2-3 minutes until it’s below 10 degrees
Add 0.5cm^3 ethanol to the flask dropwise while swirling in the ice water. You will observe a temperature increase
When the maximum temperature has been reached, repeat these steps again with another 0.5cm^3 ethanol
Clamp the flask, arrange the Quickfit apparatus as shown in the diagram, and turn on the condenser water flow
Heat gently with a Bunsen flame until you have distilled off 2-3cm^3 of ethanal into a test tube
Preparation of cyclohexene
Add 10cm^3 cyclohexanol to a small round-bottom flask
Slowly add 4cm^3 of concentrated phosphoric acid and mix thoroughly
Add a few anti-bumping granules, then set up the apparatus for reflux as shown in the diagram
Heat the mixture under reflux at about 70 degrees for 15 minutes. Adjust the heating and cooling rates to make sure all of the condensation occurs in the bottom half of the condenser
Stop heating and allow to cool for a few minutes
Arrange the apparatus for distillation
Raise the temperature and distil slowly, collecting the distillate that comes over between 70 and 90 degrees
See “purification of an organic liquid”
[OAC3] Purification of an organic liquid
Add an equal volume of sodium chloride solution to the distillate in a separating funnel, shake gently and release any pressure build-up
Allow the layers to separate and discard the lower aqueous layer
Wash the organic layer with an equal volume of water and discard the lower aqueous layer
Run the remaining organic layer into a small conical flask.
Add a few lumps of anhydrous calcium chloride and swirl the mixture, and decant the clear liquid into a container
