Explain why iron corrodes more quickly in seawater than in freshwater.
I'm getting conflicting answers from searching on Google; is it because the corrosion of iron is a redox reaction, which involves a transfer of electrons, and therefore this transfer of electrons would be quicker and happen more easily in salt water since salt water is an ionic compound and is a good conductor?
This seems to be what the majority of sources say (or at least along those lines).
I also found this:
"...in salt water the salt dissolves into the water creating ions of sodium Na +, and chlorine Cl -. This is called diffusion. These ions react with the water breaking it down or diffusing it into Oxygen and Hydrogen molecules. Thus there is more pure oxygen in salt water than fresh water.
As a result of increased oxygen, there is more Oxygen to react with the Iron thus causing faster rusting."
It's not a very reliable source, but it sort of seems right, but I don't think that diffusion is the proper label for that. And the part about water "breaking down" due to NaCl ions or "diffusing" into O2 and H2 molecules seems off to me... But it would make sense that rust occurs faster because of more oxygen. Since iron corrodes because of reactions with water and oxygen.
This looks like a good explanation. I would ignore the source that talks about diffusion and NaCl breaking down H2O into H2 and O2. That's hogwash.
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/corrosion.html
You are correct in stating that the corrosion of iron in seawater is a redox reaction, involving a transfer of electrons. This transfer of electrons occurs more easily in saltwater because saltwater is an ionic compound, made up of ions that act as conductors. The presence of ions in seawater increases its electrical conductivity, allowing for the transfer of electrons to occur more quickly.
Moreover, the dissolved salt in seawater, such as sodium and chlorine ions, can react with water molecules, leading to the formation of more oxygen in the water. This increased oxygen concentration creates a more favorable environment for the corrosion of iron. Oxygen is one of the main components required for the rusting process, as it reacts with the iron surface to form iron oxide.
However, the source you found stating that water "breaks down" or "diffuses" into oxygen and hydrogen molecules due to the presence of salt ions is not entirely accurate. Water molecules do not break down into oxygen and hydrogen molecules due to the presence of salt ions. Instead, the presence of salt ions can increase the concentration of dissolved oxygen in the water, making it more available for the corrosion process.
In summary, the faster corrosion of iron in seawater compared to freshwater is due to a combination of factors: the enhanced electrical conductivity of saltwater facilitates electron transfer, and the presence of salt ions increases the concentration of dissolved oxygen, which promotes the corrosion process.