If you burn 57.9 g of hydrogen and produce 517 g of water, how much oxygen reacted?

In order to make water (H2O) out of hydrogen (H2), you also need OXYGEN (O2) gas.  So, first write a correctly balanced equation for this reaction.

2H2(g) + O2(g) ==> 2H2O

Now, convert 59.5 g of H2 to moles, then figure out moles of H2O and then moles of O2 used to do this.  

moles H2 = 59.5 g H2 x 1 mole/2 g = 29.8 moles H2

moles H2O formed = 531 g H2O x 1 mole/18 g = 29.5 moles H2O

So, the mole ratio of H2 to H2O is 1:1 meaning that the moles of O2 used will be 1/2 that amount.  This is the case because from the balanced equation you see that 1 O2 reacts with 2 H2 and produces 2 H2O. 

Amount of O2 used = 29.8/2 = 14.9 moles

answer: cellular respiration takes in food and uses it to create atp, a chemical which the cell uses for energy. usually, this process uses oxygen, and is called aerobic respiration. it has four stages known as glycolysis, link reaction, the krebs cycle, and the electron transport chain.