[Bearhat54]

Hey guys, I had a question about a lab I am doing for Electro Chem. The question is,

Preparation of a Primary Standard Solution:
Calculate the mass of FeSO₄•(NH₄)2SO₄•6H₂O(s) required to prepare
100.00 ml of a 0.0500 mol/L solution.   
(It is a titration question, if that helps)

I think I know how to do this, you convert the 100.00 mL to L and then multiply it by the concentration (0.0500 mol/L) then use the n=m/M formula to figure out the mass. Where I am having trouble is where do I get the Molar Mass from? It can't be from all the species up there in the question, because that is ridiculous. Which species do I use for the Molar Mass?

If I am missing any information let me know!

[Arkcon]

I'm pretty sure they do mean for you to use the molecule quoted above.  What else can you use as a molar mass, if that is what you have to weigh out?

[Bearhat54]

I'm pretty sure they do mean for you to use the molecule quoted above.  What else can you use as a molar mass, if that is what you have to weigh out?

Exactly, I have no idea. I'm pretty sure that they do want me to use it, but it's MASSIVE. It would be a couple hundred g/mol at least.

[Arkcon]

Really?  I didn't try to sum it up myself, but since you need 100 mls of 0.005 M, it may not be too much.  As I recall, its a very soluble salt.  I wouldn't want to mass out enough for 1 L @ 1 M, but what do you get for what the experiment needs?

[Borek]

Do the math, you will be surprised.