Re: What does 2 grams of iron filings and 2 grams of iodine crystals make?

Iron filings (or just plain iron) is quite a reactive metal. Iron reacts 
with iodine crystals to form iron(II)iodide. Usually iron reacts with 
halides such as Chlorine and Bromine to form a mixture of both iron(II) and 
iron(III) salts but in the case of iodine the iron(III)iodide is not stable 
and usally decomposes to the iron(II)iodide.

Named and Chemical Equations:

Iron  + Iodine -----> iron(II)iodide
  Fe  +   I2   ----->     FeI2


If the iron and iodine were placed together at room temperature the 
reaction of the two would be very slow, if at all. However heating the two 
elements would speed up the formation of the iron(II)iodide.

One thing to note however is that heating the iodine with iron would have 
to be done in a sealed container as the iodine quickly sublimes(turns to 
gas) at temperatures above room temperature. Once the iodine has become a 
gas it will react more readily with the iron.

The only other thing to note is that 2g of iron is 2/55.85= 0.036 moles of 
iron whilst 2g of iodine is 2/126.9=0.016 moles of iodine.

Iron and iodine react in the ratio 1 iron: 2 iodine so the 2g (0.016moles) 
of iodine reacts with only 0.008moles of iron which is only 0.44g. This 
means reacting 2g of iron with 2g of iodine will give you 2.56g of 
iron(II)iodide and leave 1.56g of iron unreacted.

Hope that helps

David Barker