I have .400 mol of potassium sulfate (K2SO4), how can I calculate how many grams of potassium (K) I have? Does anyone know of a youtube video that will help me understand how to find the mass of just one element within a compound? Thank you!

1 mol of K2SO4 = 174 g of it. Therefore, .400 mol of K2SO4 = 174*0.4= 69.6 g. Now, 1 mol of K2SO4 contains = 2mol of K atoms or, 174 g of K2SO4 contains = 78 g of K.

Therefore, 69.6 g(.400 mol) K2SO4 contains = (78/174)*69.6 g of K =31.2 g of K.