Electrolysis Flashcards
Anode
Positive electrode, attracts the negative ion (non-metal)
Cathode
Negative electrode, attracts the positive ion (metal)
What happens when an ammeter is connected
The ammeter shows a reading
Why does a current flow through the apparatus
Positive ion gives an electron to the cathode, this flows through the circuit to the anode where an electron is given to the negative ion. This creates a flow of electrons and a current is a flow of electrons.
Solutions in electrolysis
When there is a substance dissolved in water, opposed to being molten then there are also OH- and H+ ions in the solution so these need to be taken into account when deciding which ions are at the electrodes
Rule at the cathode
If the metal is more reactive, then hydrogen is discharged
(K+, Na+, Ca2+, Mg2+, Al3+) –> H+
If the metal is less reactive, the metal is discharged
(Ni2+, Pb2+, Cu2+, Ag+)
Rule at the anode
If it is a halide, halogen gas is released
(Cl- –> Cl2) (Br- –> Br2) (I1 –> Cl2)
If it is sulphate or nitrate, oxygen is released
(SO4^2-, NO3^-) –> O2
Faraday
1 mole of electrons
96, 500 coulombs
Amp
Flow of 1 coulomb per second
Avogadros constant
6.02 x 10^23
Volume of 1 mole of gas
24, 000cm3
24 dm3
Equation for coulombs
Coulombs = current x time
Q=It
Electrolysis calculations to find the mass
- Q= It (find the coulombs)
- moles=coulombs/96,000 (find the moles)
- Find the ratio from the ionic half equation
- Multiply moles by ratio
- mass = mr x moles (find the mass)
Electrolysis calculations to find the volume
- Q= It (find the coulombs)
- moles=coulombs/96,000 (find the moles)
- Find the ratio from the ionic half equation
- Multiply moles by ratio
- volume = moles x 24,000 (find the volume in cm3)
