# Homework Help: How to multiply chemical compounds together?

1. Feb 22, 2013

### PhizKid

1. The problem statement, all variables and given/known data
$CuSO_4 \cdot 5H_20$

2. Relevant equations

3. The attempt at a solution
We never learned this. I don't even know what it means to "multiply" compounds together...doesn't make any sense to me

2. Feb 22, 2013

### Simon Bridge

In what context are you seeing this notation?

I suspect what you are seeing is the notation for a hydrate - a copper-sulphate crystal with water in it.

3. Feb 22, 2013

### PhizKid

it says to find the mass of each element. then that formula is given

4. Feb 22, 2013

### SteamKing

Staff Emeritus
If you give a complete problem statement, your chances of receiving help will increase.

5. Feb 22, 2013

### Simon Bridge

Well ... that notation normally means that each copper-sulphate molecule has 5 water molecules associated with it in the lattice. Copper-sulphate is a penta-hydrate ... heat the crystal and you see steam comes off, and you end up with anhydrous copper sulphate, which is a white powder. The water gives it that characteristic blue rhomboid crystal.

That's the raw question - but what is the context?
You are doing a chemistry course and they have reach a particular topic involving...
The mass of each element .... present... in a crystal ... in a particular concentration of solution...

Anyway:
The penta-hydrate copper sulphate compound would have 9 oxygen atoms for example... 5 from the water and 4 from the copper-sulphate.

http://en.wikipedia.org/wiki/Copper(II)_sulfate
http://en.wikipedia.org/wiki/Hydrate

Last edited: Feb 22, 2013
6. Feb 24, 2013

### Staff: Mentor

I believe this has been well explained. The dot and the right side represents the water of crystallisation.

If you need to mix a 1M solution of copper sulphate, you need to know how much to weigh out. It is important that you calculate the weight based on CuSO4•5H2O and add that to a flask of water then top it up to the 1 litre mark.

Your solution would not be 1M if you kept to the formula CuSO4 when using blue crystals of copper sulphate (these being CuSO4•5H2O, the common form of copper sulphate).