Electrolysis Flashcards
what is an electric current?
a flow of electrons or ions
define electrolysis
a process that uses an electric current to split up a substance that contains ions
define “electrolyte”
an electrolyte is the substance broken down by electrolysis and is always made up of ions
what is oxidation?
loss of electrons
OIL - oxidation is loss
what is reduction?
gain of electrons
RIG - reduction is gain
how can you tell from a half-equation whether a process is oxidation or reduction?
if the electrons are on the left of the equation they are gained and THE ION HAS BEEN REDUCED
if the electrons are on the right of the equation they have been lost and therefore the ION HAS BEEN OXIDISED
which electrons are the negatively charged ions attracted to?
the anode
what happens at the cathode
the positively charged ions are attracted and are reduced
what is the apparatus used in the electrolysis of water?
Hoffmann Voltameter
which ions will go to the cathode?
positive ions
usually hydrogen ions will go to the cathode, but ions that are lower in the reactivity series than hydrogen will go there instead if they are present
which ions will go the anode?
negative ions
if a substance ending in -ate is present (carbonate, nitrate or sulphate) it will always be the hydroxide ions (OH-) from the water that lose electrons at the anode
if a substance ending in -ide (chloride, bromide or iodide) is present in a high enough concentration the hydroxide ions remain in the solution and the “ide” is oxidised at the anode to form a halogen
the positive/negative ions that have not been attracted to the electrode stay in solution and form a third product
what are the products of the electrolysis of brine?
hydrogen gas, chlorine gas and sodium hydroxide
uses of products of electrolysis of brine?
chlorine - kill bacteria in pools and drinking water
hydrogen - fuel and margarine
sodium hydroxide - soap and paper
