Use the periodic table to determine how many grams of oxygen would be required to react completely with 859.0 g c2h2?

 (a) The balanced equation shows that 2 moles of water result from 5 moles of 
oxygen that reacts, so that is 0.4 times as many moles of water as O2. So if we 
have 2.50 moles of oxygen reacting, we produce 0.4 times that amount, or 
1.0 mole of water. 
(b) The molecular weight of acetylene is 26 and that of O2 is 32, so we can set 
up the proportion: 2.25 gm. / 52 = x gm. / 160 
Then x grams = (2.25)(160) / 52 = 6.923 grams of O2 are required. 
(c) The balanced equation shows that twice as many moles of CO2 are produced 
as we have acetylene reacting. If 78.0 grams of acetylene react, that is 3 moles 
so we produce twice that, or 6 moles of CO2. The molecular weight of CO2 is 44, 
so we have 44 times 6, or 264 grams of carbon dioxide produced. 
(d) If we collect 186 grams of CO2, the percentage yield is: 
186/264 = 0.7045, or 70.45 percent yield. 
Whew! Hope this answers all parts of your question!