if one pound (454g) of hexane combusts how many grams of water are produced?

Question

my work: 454 g C6H14 * 1 Mol C6H14/86 g C6H14 * 7H20/1 mol C6H14 * 18 g O2/ 1 MOL H2O = 665.2 grams of H2O

Answer 1

This looks ok but you have too many s.f.. I would round that answer to 665 g.