Answer
$m(Sn)=562.2g$
Work Step by Step
The following is the reaction of tin with chlorine:
$Sn + 2Cl_{2} \rightarrow SnCl_{4}$
If the mass of tin that reacts is equal to $x$, than the mass of $SnCl_{4}$ that can be obtained is equal to:
$m(SnCl_{4}) = x\times \frac{Mr(SnCl_{4})}{Mr(Sn)}\times 81.1\% \implies 1000g = x \times \frac{261}{119}\times 0.811 \implies x=562.2g$
