how many grams of oxygen does it take to produce 9.60 grams of carbon dioxide

Answer 1

1 molecule of carbon dioxide is made of 1 carbon atom and 2 oxygen atoms. The atomic weight of carbon is 12, and of oxygen is about 16. Thus, the molecular weight of carbon dioxide is 12 + 2 · 16 = 44. Of that, 32 is the oxygen, and 12 is the carbon -- if we used 32 grams of carbon to make carbon dioxide, we would need 12 grams of carbon, and we would end up with 44 grams of carbon dioxide. Therefore, if we wanted to make 1g of carbon dioxide, we would need 32/44 g of oxygen and 12/44 g of carbon.

Now, they're asking how many grams of oxygen are needed to produce 9.6 grams of carbon dioxide, so that would be 9.6 · 32 / 44, which equals pretty close to 7 grams of oxygen (and 2.6 g of carbon).