The series of reactions is:
4 NH3 + 5 O2 → 4 NO + 6 H2O
6 NO + P4 → P4O6 + 3 N2
P4O6 + 6 H2O → 4 H3PO3
4 H3PO3 → PH3 + 3 H3PO4
We multiply the first equation by a number 3 and all the
other equations by number 2, so that we get:
12 NH3 + 15 O2 → 12 NO + 18 H2O
12 NO + 2 P4 → 2 P4O6 + 6 N2
2 P4O6 + 12 H2O → 8 H3PO3
8 H3PO3 → 2 PH3 + 6 H3PO4
Then the overall reaction is:
12 NH3 + ... → 2 PH3 + ...
So calculating for PH3:
(1.10 g NH3) / (17.0306 g NH3/mol) x (2/12) x (33.9976 g
PH3/mol) = 0.366 g PH3