Electrochemistry Flashcards
(22 cards)
What is a metallic conductor
Substances which carry electrical current due to delocalised electrons
What are electrolytes of
Conduct electricity due to free moving ions when a lattic breaks down . Covalently bonded acids also form electrolyte solutions in water .
What happens when current passes through an electrolyte
Ions move through substance so pick up electrons or give electrons to power supply resulting in a chemichal reaction that breaks down the electrolyte into elements . They are decomposed by the passage of an electric current ( electrolysis )
Electrode
Metallic conductor that the power supply makes contact with the electrolyte
Anode
Positive electrode attracts negative ions
Cathode
Negative electrode , attracts positive ions metal will form here
Where will hydrogen be discharged when an ionic compound is electrolysed in an aqueous solution
At cathode unless copper , silver or gold ions are present in solution as these will be discharged instead as the metal
Where will oxygen be discharged
At the anode unless halide ions are present in high concentrations because they will be discharged as the halogen instead
What are electrodes made from
Unreactive substances like graphite or platinum
Reduction ocuurs at
Cathode , gain of electrons
Oxidation occurs
At anode loss of electrons
How is dilute sulphuric acid electrolysed
Hoffman voltameter as both products are gases and this allows the gas to be collected and measured . Produces hydrogen and oxygen .
What happens when aqueous sodium chloride is electrolysed
H gas formed at cathode from ions in the water
Chlorine formed at anode as chlorine gas
What happens when copper sulphate is electrolysed with graphite electrodes
Copper ions attracted to the cathode forming a salmon pink
Coating . Oxygen is produced at the anode
What happens when copper sulphate is electrolysed with copper electrodes
Anode is impure copper and shrinks as copper atoms loose 2 electrons and the copper metal dissolves into Ye solution
Copper gains electrons at the cathode becoming pure copper atoms and the cathod grows in side coated with copper metal . Copper metal is transferred from anode to cathode , leaving impurities behind . These may fall to the bottom or dissolve in the electrolyte , remaining in solution
What happens if the thing being electrolysed is Milton
Only one possible outcome will split into the two ions e.g. Molten zinc chloride forms zinc on cathode and chlorine on anode
How do you calculate moles of electrons
Charge / 96500
What are the uses of electrolysis
Extraction of reactive metals that are more reactive than carbon as ones lower in the reactivity series can be displaced using coke .
Purification of metals - removes traces of other elements in the metal
Electroplating - thin coating of another metal of the surface e.g. Silver playing or chromium plating steel as it doesn’t corrode . Object to be plated is the cathode and the solution contains the ions of the metal that the object is to be plated with .
What is the Chlor alkali industry
Electrolysis of brine ( concentrated sodium hydroxide ) produces hydrogen chlorine and sodium hydroxide . This is carried out in a membrane cell with two electrodes in separate compartments partitioned by a permeable diaphragm which lets solutions slowly seep through . At the anode chlorine gas is fined , at the cathode hydrugen gas is formed . OH accumulates in cathode compartment with Na making sodium hydroxide solution . Diaphragm prevents hydroxide ions moving into the anode where they would react with the chlorine produced there
What’s sodium hydroxide used for
Purify bauxite , make soap, manufacture ceramics and break down wood in paper reactions
What’s chlorine used for
Bleach hydrochloride acid antiseptics PVC and sterilise water
What hydrogen used for
The manufactur of amonium and margarine
