Balanced chemical equation: 2h2(g)+o2(> 2h2o(g) how many grams of o2 are needed to produce 118 g of h2o if the reaction has a 78.2 % yield?

You must use 134 g O₂ to produce 118 g H₂O.

M_r:          32.00    18.02  

         2H₂ + O₂ ⟶ 2H₂O

Moles of H₂O = 150.9 g H₂O × (1 mol H₂O/18.02 g H₂O) = 8.374 mol H₂O

Moles of O₂ = 8.374 mol H₂O × (1 mol O₂/2 mol H₂O) = 4.187 mol O₂

Mass of O₂ = 4.1877 mol O₂ × (32.00 g O₂/1 mol O₂) = 134 g O₂

it can be icreased by increasing pressure.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.