Electrolysis Flashcards
(22 cards)
What is an electric current
A flow of electrons or ions
Why do covalent compounds not conduct electricity
They don’t have charged particles so they consist of atoms or molecules therefore they can’t conduct electricity, even if they melt or dissolve in water.
Why do ionic compounds conduct electricity only when molten or in solution
Ionic compounds have charged particles but can only conduct if it is molten or dissolved in water because only in the liquid or aqueous state can the ions move to the oppositely charged electrode.
Sodium chloride electrolysis
Diaphragm cell
Hydrogen gas at cathode
Chlorine gas at anode
Sodium hydroxide in solution
2H + + e- ——> H2
2Cl- ——> Cl2 + e-
Uses:
- chlorine sterilises water
- hydrogen for Haber process and to change oils and fat into margarine
- sodium hydroxide chemical industry for soap and bleach
Copper sulfate electrolysis
Copper : cathode (Cu2+ + 2e- ——> Cu)
Hydroxide : anode (
Electrolyte definition
Liquid that conducts electricity
Electrolysis definition
Separation of an ionic compound using electricity
Cation/cathode
Positively charged ion/ negatively charged electrode
Anion/ anode
Negatively charged ion/ positively charged electrode
Electrode definition
Terminals of battery dipping into an electrolyte
Inert definition
Unreactive atom
Definition of reduction and oxidation
Reduction : gaining electrons, occurs at the cathode
Oxidation : losing electrons, occurs at the anode
Lead bromide products
Lead, bromine
What does electrolysis involve
It involves the formation of new substances when ionic compounds conduct electricity
Sulfuric acid products
4 hydrogens, 1 oxygen
Sodium chloride products (L)
2 sodiums, 1 chlorine
Sodium chloride products (aq) diaphragm cell
Hydrogen, chlorine
- titanium anode
- mild steel cathode
Copper sulfate (aq)
2 coppers, 1 oxygen
Rules of electrolysis: cathode
Metal, except with reactive metals (K Na Li Mg) in which case H2 gas is produced plus a solution of metal hydroxide
Rules of electrolysis: anode
Non metal, except sulphates in which case O2
Electroplating
You put what you want to electroplate at the cathode (as metals go to the cathode) and a layer of metal is electrolysed onto your item. Corrosion resistant and pretty
Purify copper
A large lump of impure copper is used at the anode and the cathode is made of pure copper. That’s the anode, instead of anions losing electrons, neutral copper atoms lose electrons to become copper ions ( cu -> cu2+ +2e- ) , they then move through the electrolyte to the cathode where they become copper atoms again ( cu2+ +2e- -> cu ) The anode loses mass as copper atoms leave it and the cathode gains mass as copper atoms join it. The impurities sink to the bottom as a pile of sludge.
