Question

how many moles of h2o are produced when 64.0 g c2h2 burns in oxygen?

Answer 1

moles C2H2 = 64 g divided by 26.04 g/mol = 2.46 moles

  Now go back to the equation. Can you see that the number of moles of C2H2 and the number of moles of H2O produced are the same

  So if you burn 2.46 moles of C2H2 then you should produce 2.46 moles of water