chemical equation question

For part e, I don't understand how the equation is constructed. The paragraph mentions the addition of water to the flask as well. However in the equation, water does not act as reactant. Why is that?

I came up with 3I₂ +2H2O +2HS -> 6HI +2S +O2 but this is wrong.

Why?

Thanks

iodine is reduced to iodide
hydrogen sulphide is oxidised to sulphur

Write yourself two half equations and then combine them.

No water is needed.

Water isn't a reactant. It's just a liquid to store the aqueous solution. The 600cm^3 is to just throw you off.

This is quite hard to identify. Are you suggesting that each time I construct a chemical equation, it is a good idea to write out the redox equations first? Thanks

Depends. If it makes it more understandable to you then it might be worthwhile.

However, ignoring water which is just a solvent here, all you are left with is

H₂S + I₂ --> S + HI

which is not exactly difficult to balance and add state symbols to, is it?

Sure it would be easy if I know which are the reactants. But sometimes there are other products formed and that isn't mentioned in the question. Is there any other ways to find out whether water is just a solvent ? Thanks

Are you Y13? I don't want to seem mean but by this stage you ought to have some sort of chemical intuition and realise what the reactants and products are in what is a fairly straightforward process in this case.

Think why would the water be there. You are making hydroiodic acid. Acids such as this are solutions in water. Conc. HCl for example is 37% HCl and the rest is water.

I guess you just have to keep doing past questions as you clearly have been.

Yes, that is my area of weakness. Thanks for the help.

You are not alone. Many students find it difficult to develop the skills that they will need at university when they are in the sixth form. I force my students to do it by giving them very hard questions to do yet some still cannot move from needing a step by step method for every single type of question they might come across, to using their knowledge and working things out for themselves, in other words to problem solve.

When you see a question you should read it very carefully and not necessarily all at once. Every part of it will tell you something. Breaking down the given information into chunks and then seeing what you have been told line by line rather than reading the whole question and thinking 'Where on Earth do I start?'

I do this for my students by writing my own questions. If you would like one to try then let me know.