[casper248]

You have 47 ml of a protein solution. You want to add 0.39 g of ammonium sulfate per ml. How much ammonium sulfate do you need to add?

[chenbeier]

What do think what you have to do with the numbers.

[casper248]

No idea it has been 10 years since I have seen biochemistry. This is my first semester ongoing. Any help would be appreciated!
 

[Babcock_Hall]

It is a forum rule (see red link) that you must show your attempt before we can help you.  What do you remember about units cancellation?

[Arkcon]

No idea it has been 10 years since I have seen biochemistry. This is my first semester ongoing. Any help would be appreciated!
 

This question:

You have 47 ml of a protein solution. You want to add 0.39 g of ammonium sulfate per ml. How much ammonium sulfate do you need to add?

Doesn't use biochemistry.  Read it out loud.  Change some numbers to make it easier: You need to add 1 teaspoon of Kool-Aid mix per quart, you have 4 quarts, how many spoons do you need?

[casper248]

If I need 0,39g per ml of (NH4)₂SO₄ in a solution of 47 ml will get 18,33g in total

[Arkcon]

That is the correct arithmetic.  It should give you the proper result in a biochem experiment.  However, you may lose points, on an exam, for incorrect use of significant figures.