If you reacted 12.0 g of C7H8O2 (124.14 g/mol) with 200.0 g of O2, (31.998 g/mol) what mass (in g) of H2O (18.015 g/mol) can you theoretically make?

Answer 1

convert to moles
write the equation -- it will tell you how many moles of H2O to expect
convert back to grams.