Answer
Sn: $ 78.77 \% $
O: $ 21.23 \% $
Work Step by Step
1. Calculate the molar mass of $SnO_2$:
$ SnO_2 $ : ( 118.7 $\times$ 1 )+ ( 16.00 $\times$ 2 )= 150.70 g/mol
Sn:$$\frac{ 118.7 \times 1}{150.70} \times 100\% = 78.77 \% $$
O:$$\frac{16.00 \times 2}{150.70} \times 100\% = 21.23 \% $$
