Practicals

Question 1

Method for preparing a 250cm^3 solution of sodium hydrogen sulphate

Answer 1

1.Calculate the mass of sodium hydrogen sulphate needed to produce a solution of concentration 1mol
2. Take the mass of a weighing bottle and record it, weigh the the mass calculated approximately and record true value
3. Pour content into a beaker and rinse with distilled water to transfer all powder
4. Add 100cm^3 of distilled water to beaker and use a glass rod to stir until solid dissolves
5. Using a funnel pour solution into a volumetric flask then rinse with distilled water
6. Use a pipette to fill solution up to the mark
7. Close the stopper and invert to mix the solution

Question 2

Method for carrying out an acid base titration

Answer 2

1. Fill a labelled beaker with sodium hydrogen sulfate solution, use this to rinse out the burette then fill it
2. Fill a labelled beaker with sodium hydroxide, rinse a 25cm^3 pipette with it, measure out, pour into conical flask
3. Add a few drops of indicator to conical flask and note the colour
4. Record the initial burette reading, begin to titration solution slowly swirling the flask throughout
5. When the solution changes colour record the final burette reading
6. Repeat until 3 concordant results are obtained

Question 3

Method for measuring enthalpy change

Answer 3

1. Weigh out 4g of anhydrous copper sulfate in a closed weighing bottle
   2.measure 25cm^3 of distilled water, pour into polystyrene cup, measure temperature every Min for 3 minutes
2. At 4th minute add powder and stir continually, record temp at 5th minute and continue every minute
   4.Construct a table of temperature against time
   5.Plot a graph for temperature against time, extrapolate two line of best fit to calculate temp change

Question 4

Method for calculating rate of reaction between HCL and sodium thiosulfate as temperature is changed

Answer 4

1.Add 10cm^3 of HCl into a labelled test tube
2. Add 10cm^3 of sodium thiosulfate to a labelled test tube, place over a cross, insert a thermometer
3. Record starting temp, add 1cm^3 of acid to sodium thiosulfate and start a timer, record time it takes for cross to become obstructed, record final temp of solution
4. Using two new samples of HCL and sodium thiosulfate place test tubes in a water bath below 55°c and allow to heat, use a thermometer to check temp
5. Repeat experiment at different temperature intervals obtaining values for 5 different temperatures

Question 5

How to test for an alcohol

Answer 5

Add acidified potassium dichromate if a 1° or 2° alcohol is present an orange solution turns green
(Also tests for aldehydes)

Question 6

How to test for carboxylic acids

Answer 6

Add sodium hydrogen carbonate

Question 7

How to test for halogenoalkanes

Answer 7

Add warm sodium hydroxide, acidify with nitric acid, add silver nitrate

Silver halide precipitate forms
Chloride is white
Bromide is cream
Iodide is yellow