Hydrated sodium stannate has the percentage composition of 44.50% Sn, 17.24% Na, 35.99% O, and 2.27% H. Determine what the correct formula is for hydrated sodium stannate. The correct order of elements is

Na_aSn_bO_c•d H₂O

First, assume 100 g of compound for simplicity. Then calculate the quantity of each element in moles, n.

Since the waters of hydration are the only source of hydrogen, it is possible to calculate the quantity of water (in moles) present.

So far, we can fill in the atom subscripts as

Na_0.7499Sn_0.3749O_c•1.126 H₂O

But we still don't know c.

Finally, we fill in the subscript on O…

Na_0.7499Sn_0.3749O_1.123•1.126 H₂O

But this is a violation of definite proportions, so we normalize to the least-common-multiple (normalize to 1 with 0.3749)

Na₂SnO₃•3 H₂O