Question on Hydrates and Reactions

[rosyposy]

Hey! I am currently working on a project where I have to react copper (II) chloride dihydrate (dissolved in water) and aluminum. When writing the equation and the ionic equation for this, would you include the dihydrate in the formula since it’s dissolved in water and no longer in its crystalline form or would you still write it as CuCl2.2H2O, can you also provide an explanation for the correct way to write since I am really confused as some sites write it with the H2O and some don’t. Thank you!

 

[jim mcnamara]

The water of hydration - .2H₂0 - adds mass to the molecule. So, if are going to get a dry weight to assay some reaction in a solution you have to include it. Is that what you are asking? You can write the reaction ignoring the extra mass but I do not see any immediate benefit other than teaching an introduction.
Practical aspect is what you have dictates what you do:
Copper chloride appears as a yellowish-brown powder (the anhydrous form) or a green crystalline solid (the dihydrate). The green stuff is usually what you have. If have the brown stuff you would measure the mass of copper chloride with no water to worry about.

 

[rosyposy]

Hey, so I am only weighing the copper retrieved from the reaction to find the concentration of the original solution using stoichiometry, but I also need to write the formula for the whole reaction with states so I was just asking if I would write the copper (II) chloride dihydrate as a dihydrate since it is dissolved in water and I’m not sure if you are supposed to write dihydrates as aqueous since they exist in crystalline form.

 

[symbolipoint]

There's a web page, interesting, but not certain if it helps you:
reaction of aluminum metal with cupric chloride
https://justonly.com/chemistry/chem201/students/handouts/rxn_al_cu.pdf

 

[Borek]

There is no simple yes/no answer to your question.

A lot depends and what you want to show. Every way of writing the reaction has its own applications and makes sense in different contexts.