AQA A Level chemistry

A student bubbles chlorine gas through a solution of sodium iodide . A reaction takes place.
Why would a brown solution form please?
I understand the a black solid forms due to the iodide

Reply 1

user23184

When you bubble chlorine gas through sodium iodide, the following reaction would take place:

Cl2 + 2NaI -> I2 + 2NaCl

As chlorine is more reactive than iodine, a displacement reaction occurs to form sodium chloride and iodine solution.

Hence, sodium chloride will be colorless and iodine will appear as a brownish-yellow solution

Reply 2

TypicalNerd

Original post by anon25x

A student bubbles chlorine gas through a solution of sodium iodide . A reaction takes place.
Why would a brown solution form please?
I understand the a black solid forms due to the iodide

User23184 has correctly identified the reaction taking place, but hasn’t fully justified that iodine is kind of soluble in water, but not massively so. As such, it will impart a colour on the solution and you won’t get a mixture with a colourless solution and a black precipitate.

In the case of the solution formed in this reaction, you’d expect it to be brown, as aqueous iodine typically takes on this colour. You may also get a bit of black precipitate, but you wouldn’t necessarily be expected to know this at A level.