please help with this stoichiometry problem?

Question

ethane gas (C2H6) burns in air to form carbon dioxide and water. how many grams of carbon dioxide are produced for each 8.00 grams of water produced?

Answer 1

First balance the equation (you just need the ratio of carbon dioxide to water formed).

2 C2H6 + 7 O2 >>> 4 CO2 + 6 H2O

The ratio is 2 CO2 to 3 H2O:
If we form 1 mole of water, we would make 2/3 mole of CO2.

Determine moles of water formed:
8.00g/18g/mole = 0.444

O.444 x 2/3 = moles CO2 = 0.296mole
0.296mole x [12 = (2x16)]g/mol = 13.02g

Another way:(skipping some of the more elementary steps) we can see from the equation that for every 18g (1 mole) of water formed we would make 2/3 x 44g (molecular weight of CO2) so:

8/18 x 2/3 x 44g = 13.04g

Note: the slight difference in answers is due to rounding off 8/18 as 0.444 or leaving it as 0.444(repeating) during calculation.