How many mols do you need? That's L x M = 0.250 L x 0.220 M = ?
Then mols = g/molar mass. You have molar mass and mols, solve for grams.
What mass, in grams, g, of solid ammonium persulphate, (NH4)2S2O8 needed to prepare 250.0 mL of a 0.220 M solution?
Molar mass of (NH4)2S2O8 = 228.18 g/mol
3 answers
0.250 L x 0.220 M = .055 mols. .055x228.18=12.55g?
If you typed in all of the significant figures n the problem, then the 0.220 M allows you to use 3 decimal places so I would round that to 12.6 g
2 answers