Electrochemistry Flashcards
Electrolysis definition
Electrical energy used to cause a non-spontaneous chemical reaction to occur
Which side of battery electrons come out from
Short side
Which side of the battery are the anode and cathode connected to
Anode connected to the positive side (long side) –> positively charged
Cathode connected to the negative side (short side) –> negatively charged
Cathode and anode attract what
Cathode attract cation anode attract anion
What happens to binary ionic compounds after electrolysis
Decompose to form a metal and a non metal
Molten compounds what happens to the metal
Silvery liquid collected at bottom of the reaction vessel (near the cathode)
What state is bromine at room temp
liquid
OH- oxidation equation
4OH- –> O2 + 2H2O + 4e-
Cathode selective discharge electrochem series
Less reactive metals accept ions more readily and will be discharged at the cathode
More reactive have greater tendency to form ions and will remain in the electrolyte
Electrochem series
Same as reactivity series
Conc of anion (halides)
Greater conc will be preferentially discharged over OH-
What are the inert and non inert electrodes
Inert: Platinum, graphite
Non intert: Copper, Silver
Electrolysis of water equation
Anode:
4OH - —> O2 + 2H2O + 4e-
2H2O —> O2 + 4e- + 4H+
Cathode:
2H+ + 2e- –> H2
2H2O + 2e- –> H2 + 2OH-
Overall: 2H2O –> O2 + 2H2
Electroplating anode cathode electrolyte
anode: plating metal
cathode: substance to be plated
electrolyte: must contain the ions of the plating metal
What happens in the purification of copper
As one copper atom is oxidised at the anode to form copper (II) ion and enters the solution, a copper (II) ion is reduced at the cathode to form copper and is deposited on the cathode
What is a simple cell
A spontaneous redox reaction that produces electrical energy
Simple cell what is cathode/anode
More reactive is anode
Less reactive is cathode
Explain simple cells
More reactive metal undergoes oxidation at the anode and electrons flow through the wire to the cathode (produces current and cause deflection in galvanometer)
Cathode provides surface for electron transfer and ions at bottom of Electrochem series will be dis charged
What kind of acid does chlorine dissolve to form
Oxidising acid that will bleach universal indicator
The anode go from green to red to colourless (bleached)
Colour change (indicator) at cathode when hydrogen is discharged
Go from green (original) to red (when H+ ions are there) to greenish-blue (when they hydrogen gas is no longer there)
Aqueous copper (II) sulfate electrolysis overall equation
2CuSO4 + 2H2O –> O2 + 2H2 + 2H2SO4
Phrasing for copper being deposited
Reddish-brown solid deposited at the cathode
Hydrogen gas
- Flammable gas
- An electrical insulator and can stop the production of an electrical current when formed at the cathode
Fuel cell equations
Anode (hydrogen)
H2 + 2OH- –> 2H2O + 2e-
Cathode (oxygen)
O2 + 2H2O + 4e- –> 4OH-
