Question

Ammonia (NH3) burns in air to form nitrogen dioxide and water. Calculate grams of nitrogen dioxide produced if 4.0 grams of ammonia are consumed

Answer 1

the balanced equation for the above reaction is;
4NH₃ + 7O₂  --> 4NO₂  + 6H₂O
stoichiometry of NH₃ to NO₂ is 4:4
the number of NH₃ moles consumed are - 4.0 g / 17 g/mol = 0.24 mol
number of NH₃ moles reacted are equivalent to number of NO₂ moles formed 
therefore number of NO₂ moles formed - 0.24 mol x 46 g/mol = 11.04 g
mass of NO₂ formed is 11.04 g