Question

Industrially, nitric acid is produced by the Ostwald process represented by the following equations:
4NH3 +5O2 = 4NO +H2O
2NO +O2 = 2NO2
2NO2 +H2O = HNO3 +HNO2
What mass of NH3 (in grams) must be used to produce 1.0 ton of HNO3 by the above procedure, assuming an 80 percent of yield in each step?(1ton=200 lb,1lb=453.6g)

Answer 1

Note the first equation isn't balanced. Note that 1 ton = 2000 lb. Note that the third equation isn't what I've seen for the Ostwald process but I've used what you posted.

You want 2000 lb x 453.6 g/lb x (1/0.8) x (1/0.8) x (1/0.8) = approx 2E6 g to be produced considering the 80% yield in each step but that's an estimate and you need a better answer than that.
So NH3 must be
2E6 g HNO3 x (2 mol NO21 mol HNO3) x (2 mols NO/2 mols NO2) x (4 molsNH3/4 mols NO) = ? g NH3.

Post your work if you get stuck.