1
Q
How do you determine the formula of a hydrated compound by weighing and heating the salt to constant mass?
A
- Weigh and evaporating basin
- Add some hydrated solid and weigh the evaporating basin and solid
- Heat to constant mass
2
Q
How do you use deflection of a stream of liquid to show polarity or lack of it?
A
- Place a liquid in a burette and place a beaker underneath the jet
- Open the tap and allow a small stream of liquid to come from the burette
- Hold a charged polythene rod close to the liquid but not touching and record any deflection
- To compare polarity use two steams from two burettes simultaneously
3
Q
How do you determine the solubility of chlorine and iodine in aqueous and non aqueous solvents?
A
- Add 1cm3 of each of the aqueous halogen solutions into separate test tubes
- Add equal volumes of saturated hydrocarbon solvent e.g. hexane, shake by stopper and invert
- Allow two layers to settle and observe colour change
4
Q
How do you produce a reactivity series of the halogens using displacement reactions?
A
- Add 1cm3 of each of the aqueous halogen solutions into separate test tubes
- Ad 1cm3 of potassium chloride to each and record any colour change
- Repeat with potassium bromide/iodide
- Starch could be added to detect iodine
5
Q
How do you carry out the reactions of the halides with concentrated sulfuric acid and concentrated phosphoric acid
A
- Place 1 spatula of solid potassium chloride in a test tube
- Add a few drops of concentrated sulfuric acid and record any observations
- Test the gas evolved
- Repeat with the rest of the halogens
- Repeat with concentrated phosphoric acid
6
Q
How do you ensure accuracy when carrying out a titration?
A
- Rinse the apparatus with the appropriate solution
- Add the solution dropwise just before the end point
- Swirl the flask
- Read the burette at the bottom of the meniscus
7
Q
How do you carry out a titration?
A
- Rinse the pipette with the solution to be transferred to the conical flask
- Using the pipette and pipette filler transfer 25.0cm3 of the solution into the conical flask
- Rinse the burette with the solution to be put in it
- Fill the burette with the bottom of the meniscus on the line
- Add 3-5 drops of a suitable indicator to the conical flask
- Add the solution from the burette while swirling the conical flask, record the point where the indicator just changes to two decimal places
- Repeat to achieve two concordant results
8
Q
How do you prepare a solution of known concentration ?
A
- Calculate the mass of solid required for the solution
- Weigh the solid on a top pan balance in a beaker
- Dissolve the solid in a small volume of water
- Transfer the solution to the appropriately sized volumetric flask
- Rinse the beaker and glass rod with deionised water and add the washing to a volumetric flask
- Make up to the mark with deionised water and stopper and invert to mix
9
Q
Flame test
A
- Dip the nichrome wire into concentrated hydrochloric acid
- Dip the wire in the test solid
- Hold the wire in the blue bunsen flame
- Note the colour of the flame
10
Q
What is the method of preparation of a halogenoalkane?
A
- Place 10g of sodium bromide in a pear shaped flask
- Add 7.5cm3 of Butan-1-ol and 10cm3 of water
- Lower into a beaker of cold water
- Add 10cm3 of concentrated sulfuric acid slowly and with stirring
- Add some anti bump granules
- Gently reflux the mixture
- Distill off impure bromobutane
- Remove unreacted butan-1-ol by shaking with concentrated hydrochloric acid in a separating funnel
- Dry the impure product
- Purify the product using simple distillation
11
Q
Draw a diagram for refluxing a halogenoalkane
A
in book
12
Q
Draw a diagram for the distillation of a halogenoalkane
A
in book
13
Q
How do you remove acidic impurities using a separating funnel?
A
- Place the impure distillate into a separating funnel
- Add a portion of sodium carbonate solution
- Stopper and shake
- Release the pressure at regular intervals by inverting and opening the tap
- Allow to stand until layers settle and separate, then run off lower layer into a beaker
- Decide which is the aqueous layer by adding water, whichever increases in size discard
14
Q
How do you dry the product?
A
- Place the impure liquid product in a beaker or conical flask
- Add a spatula of drying agent e.g. Magnesium sulfate
- Add more drying agent until the liquid is clear
- Decant the liquid
15
Q
How do you prepare alcohols from halogenoalkanes using alkali
A
- Place the halogenoalkane in a pear shaped flask
- Add dilute sodium hydroxide solution
- Add some anti bump granules
- Heat under reflux
- Distill off the alcohol
16
Q
How do you prepare a carboxylic acid from the corresponding alcohol using acidified potassium dichromate solution
A
- Add excess acidified potassium dichromate solution to a pear shaped flask set up for reflux
- Add antibump granules
- Add a volume of primary alcohol slowly down the condenser from a dropping funnel, and cool in a water bath
- Remove the water bath and heat the mixture under reflux
- Rearrange the acid for distillation and distill if the acid.
17
Q
How do you prepare the aldehyde
A
- Add excess acidified potassium dichromate solution to a pear shaped flask
- Add antibump granules
- Add a volume of primary alcohol
- Assemble the apparatus for distillation - this removes the aldehyde from the oxidising mixture immediately and prevents further oxidation
18
Q
How do you prepare the ketone?
A
- Add excess acidified potassium dichromate solution to a pear shaped flask set up for reflux
- Add anti-bump granules
- Add a volume of secondary alcohol slowly down the condenser from a dropping funnel, and cool in a water bath
- Remove the water bath and heat the mixture under reflux
- Rearrange the apparatus for distillation and distill off the ketone.
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