How many atoms of oxygen are in 4.6 grams of copper sulfate

m (CuSO4*5H2O) = 424.0 g

M (CuSO4*5H2O) = 249.68 g/mol

n=m/M

n (CuSO4*5H2O) = 1.7 mol

There are 9 atoms of oxygen in each formula unit of CuSO4*5H2O. Therefore,

n (O) = 8.5 mol

M (O) = 16 g/mol

m=M*n

m (O) = 135.6 g