Section 4- Elements of the Sea Flashcards
(10 cards)
What is the pattern of substances which are formed at the cathode?
If the metal is less reactive than hydrogen, then it will be formed at the cathode. This is because hydrogen will react with ions in the aqeous solution over the metal ions.
If the metal ions are more reactive than the hydrogen ions, including group 1 and group 2 metal ions as well as aluminium, then Hydrogen will be formed at the cathode. This is because they will react with ions in solution over hydrogen.
What is the pattern of substances which will form at the anode?
Oxygen is always formed from the oxidisation of hydroxide ions, unless there is the presence of halides which are concentrated, if they are however not concentrated and are dilute, they will not form at the anode over oxygen. You could test for oxygen with the glowing wooden splint being reignited.
How is chorine produced indistrially?
Where is this commonly sourced from?
Electrolysis of brine. The brine must be concentrated otherwise the chlorine wont be formed at the anode, rather the oxygen will be.
Commonly sourced from sea water.
How is chorine used to displace iodine and bromine to form them in they standard states?
Chlorine is more reactive than then, so can oxidise them to become a chloride ion and leave them in their diatomic natural state.
Explain a sodium thiosulfate titration.
React Potassium iodate IO3- with Iodide ions I- to produce Iodine. Here Iodide is oxidised, you should have the oxidising agent potassium iodate in exess to produce as more Iodine as possible. This will form a yellow coloured solution. You should then react the iodine with Thiosulfate solution, which will convert the iodine back to iodide ions, decolourising the solution. When the solution begins to turn a very faded yellow colour, you should place on a white tile and add starch solution to get a blue black colour. This will make the colour change more apparent. You should then dropwise titrate the thiosulfate whilst swirling the solution until the colour changed from blue to back to colourless, indicating that no iodine is longer present.
A way to remember that iodine is purple in hexane.
It is used in chromatograph as an agent to locate organic materials. Hexane is organic, so it turns it purple/violet
What can be used to produce all hydrogen halides with the addition of an ionic halide?
Concentrsted phosphoric acid
If you want to be funny and use concentrated sulfuric acid, them you will get slightly different things because it is an oxidising agent, meaning it takes electrons.
What happens to:
Cl-
Br-
I-
Like normal, Cl- can be reacted with to produce HCl, this is because sulfuric acid is not a strong enough oxidising agent to oxidise a chloride ion
With Bromide, sulfur dioxide is produce alongside bromine and water
With iodide, H2S (hydrogen sulfide) is produced alongside water and Iodine.
What does ammonia react with a hydrogen halide to produce?
An ammonium halide
