Required Practicals

Magnesium and HCl:

• Measure out 20 cm3 of dilute hydrochloric acid using a measuring cylinder and pour it into a conical flask and place it on a mass balance

• Record the initial mass of the conical flask with the acid

• Now add a magnesium ribbon and then quickly plug the flask with cotton wool to stop the acid spitting out

• Start your stopwatch and take readings of the mass at regular intervals (every 10 seconds)

• Plot your results on a graph with time of the x and loss of mass on the y

• Repeat with different concentrations of hydrochloric acid but keep the volume the same

Sodium Thiosulfate and HCl:

• Measure 20cm3 of dilute sodium thiosulfate using a measuring cylinder and pour it into a conical flask

• Draw a black cross on a piece of paper and place the flask on the paper so the cross is under the middle of the flask

• Next, measure 10cm3 of hydrochloric acid using a measuring cylinder and add it to the flask and start your stopwatch

• Watch as the reactants form a yellow precipitate and stop the stopwatch when you cannot se ethe cross when looking directly down at it

• Repeat the experiment with different concentrations of HCl but keep the volume of sodium thiosulfate constant

Paper Chromatography:

• Draw a line with a pencil 3cm from the bottom of the piece of paper and put a dot of your mixture on the line

• Use a rod to secure the paper over a beaker and use a pipette to add distilled water so it is just below the pencil line

• Watch as the water moves up the paper which also moves particles in the mixture upwards

• The lighter particles should get carried further up the paper

• Measure the distance each dot has moved up the paper and calculate their Rf values using Distance Substance Moved / Distance Water Moved

• You can compare it with known values to see what substances the mixture contains

Identifying Metal Ions:

• Clean a platinum wire loop with HCl and then hold it in a blue flame until it burns without any colour

• Then dip the loop back in the HCl and then in your metal sample that you want to test

• Heat the substance over a blue flame and record the colour and record the colour

• Then clean the wire with the acid and blue flame again and repeat it with a different sample

• Lithium ions are Crimson, Sodium ions are Yellow, Potassium ions are Lilac, Calcium ions are Orange, Copper ions are Green

Purifying Water (Distillation):

• First test the water’s pH with a pH meter, and if its too high or low you can neutralise it with titration

• Test the water for sodium chloride, where sodium can be tested using a flame test turning yellow and chloride ions react with nitric acid and nitrate solution to form a white precipitate

• Then pour your water into a conical flask and place it on a gauze on top of a Bunsen burner

• Connect this to a beaker of ice with a test tube in using a bung and tube

• Boil the water to form steam which condenses back in the other test tube, leaving the dissolved salts in the flask

• Retest the pH and for sodium chloride to see if it has been removed and that the water is neutral

Testing for Anions:

• Carbonates - Use a dropping pipette to add a dilute acid (HCl) to your solution. Then bubble the gas produced through limewater and if it turns cloudy it is a carbonate

• Sulfates - Use a dropping pipette to add dilute HCl and barium chloride solution to your solution. If it forms a white precipitate then it is a sulfate

• Halides - Use a dropping pipette to add dilute nitric acid and silver nitrate solution to your solution. Chloride forms a White precipitate, Bromide forms a Creamy precipitate, Iodide forms a Yellow precipitate

Testing for insoluble metals:

• Use a dropping pipette to add drops of sodium hydroxide to your solution

• Calcium forms a White precipitate, Copper forms a Blue precipitate, Iron(II) forms a Green precipitate, Iron(III) forms a Brown precipitate, Magnesium forms a White precipitate, Aluminium forms a White precipitate which redissolves in excess sodium hydroxide solution to form a colourless solution.