Question

What mass of KIO3 is needed to convert the copper in 0.2750 g of CuSO4 · 5H2O to
Cu(IO3)2?

Answer 1

Long way and short way. mm stands for molar mass. I've rounded molar masses and not watched the number of significant figures.
Short way:
0.2750 g CuSO4.5H2O x (2*mm KIO32/mm CuSO4.5H2O) = ?estimated 0.47 g.
Long way:
CuSO4.5H2O + 2KIO3 ==> Cu(IO3)2 + K2SO4 + 5H2O
mols CuSO4.5H2O = grams/molar mass = 0.2750/249.5 = 0.001102
0.001102 mols CuSO4.5H2O x (2 mols KIO3/1 mol CuSO4.5H2O) = 0.002204 mols KIO3.
grams KIO3 = mols x molar mass = 0.002204 x 214 = about 0.47 g