Chemistry RPA

All required practicals and tests

Creating a soluble salt

• add carbonate to the acid in a beaker and stir

• continue adding until carbonate is in excess, shown by excess solid

• filter (the reaction mixture) to remove the excess carbonate

• heat the solution using a water bath/electric heater/bunsen burner to crystallisation point

• leave the solution to crystallise

• pat crystals dry with filter paper

Titration for unknown acid

• measure the volume of acid with pipette and place under white tile

• add few drops of indicator to the acid

• add alkali solution to acid using burette until indicator colour changes

• rough titration to find approximate end point

• add dropwise near the endpoint and swirl

• record volume of alkali solution added then repeat and take a mean

Titration for unknown alkali

• measure the volume of alkali with pipette and place under white tile

• add few drops of indicator to the alkali

• add acid solution to alkali using burette until indicator colour changes

• rough titration to find approximate end point

• add dropwise near the endpoint and swirl

• record volume of acid solution used then repeat and take a mean

electrolysis

tbc

Effect of change in mass/volume of alkali on highest temperaure reached

• measure volume of acid with a measuring cylinder

• pour acid into a suitable container (e.g. polystyrene cup)

• measure the initial temperature of acid with a thermometer

• add a known mass/volume of alkali and stir

• measure the highest temperature reached then repeat with different masses/volume of alkali

when repeating the whole investigation

• use the same starting temperature

• use the same volume of acid each time

• use the same concentration of acid each time

Concentration of sodium tthiosulfate affects rate of reaction

• measure volume of sodium thiosulfate then place in conical flask

• measure volume of hydrochloric acid

• place on cross

• add hydrochloric acid to flask and swirl

• start stopclock / stopwatch

• measure time for cross to become no longer visible

or

• connect to a gas syringe

• measure time for fixed volume of gas to be produced

• repeat and find mean

• repeat for different concentrations of sodium thiosulfate

Chromatography

• draw pencil start line

• place spot of ink on start line

• place suitable solvent (water, ethanol) in beaker

• place paper in solvent so solvent is below start line

• use a lid

• allow solvent / dyes to travel up paper (until near top)

• dry then count spots

Flame test for metal ions

• dip nichrome wire in powder/solution

• hold at edge of blue part of Bunsen flame

• metal will change colour

• lithium - crimson

• sodium - yellow

• calcium - orange/red

• copper - blue/green

• potassium - lilac

test for carbonate ions

• react sample with HCl

• if bubbles are made, collect with gas syringe

• mix bubbles with limewater

• if limewater urns cloudy, is a carbonate ion

• bubbles are CO₂

test for halide ions

• dissolve sample in distilled water in test tube

• add dilute nitric acid

• add silver nitrate solution using pipette

• halide ions will produce a precipitate

• chloride - white precipitate

• bromide - cream precipitate

• iodide - yellow precipitate

test for sulphate ions

• react sample with HCl to remove any carbonate ions

• add barium chloride solution

• sulfate ions form a white precipitate of barium sulphate

test for aqueous metal cations (x^y+)

• react sodium hydroxide with sample

• solid metal hydroxide will form (precipitate)

• Aluminium (Al³⁺) - White

• Calcium (Ca²⁺) - White

• Magnesium (Mg²⁺) - White

• Copper (Cu²⁺) - Blue

• Iron (Fe²⁺) - Green

• Iron (Fe³⁺) - Brown