The mass (in grams) of FeSO4*7H2O required for preparation of 125 mL of 0.90 M

Answer 1

You want how many moles? That's mols = M x L = = 0.90 x 0.125 = ?
Then grams = mols x molar mass. You know mols and molar mass. Solve for grams. Post your work if you get stuck.

Answer 2

Stuck