required practicals Flashcards
making soluble salts
paper 1
-take a base(powdered copper oxide) and mix with heated (sulphuric) acid to cause a neutralization reaction that produces a salt solution
-add copper oxide in excess until you can see unreacted powder at the bottom of the beaker
-filter,then heat the solution in an evaporating basin on a beaker of water over a tripod,gauze and bunsen burner
-once the water has evaporated,dry the crystals produced by placing on filter paper
Electrolysis
Paper 1
-place Carbon electrodes(inert) in a solution of salt to be electrolysed, ensuring the don’t touch.
-connect the terminals to a battery or (DC) power supply.
-negative electrode:cathode positive electrode:anode
-the solution contains H+ and OH- ions.if sodium chloride solution, also Na+ and Cl- ions
-if the metal ion is more reactive then hydrogen it will stay in solution and hydrogen gas will be reduced at the cathode to make H(2) gas if not the metal will be reduced instead
-if the non metal ion is a halide it will be oxidised at the anode if it’s not a halide oxygen gas is made at the anode
Exo-Endo
-measure 30cm(3) of dilute hydrochloric acid through a meauring cylinder
-move acid into a polystyrene cup
-stand this cup inside a beaker
-use a thermometer to measure the tempereture of the acid
-then use a cylinder to measure 5cm(3) of sodium hydroxide solution
-and add this to cup
-add a plastic lid to the cup while maintaining the thermometer
-gently stir solution
-look at the temp chnage
-when it stops changing
-when it stops changing we have reached max tempereture
-then repeat using 10cm(3) of sodium hydroxide solution
-repeat several times increasing volume of sodium hydroxide by 5cm(3) each time until you reach 40cm(3)
-repeat whole experiment once more to calculate mean tempereture change
variables in the temperature change practicle
-independent variable:volume of alkali used
-dependant variable:max temperature reached
-control:concentration of reactants,initial temp
