a moli a/2 moli
2H2 + O2 --> 2H2O
2 1 2
1 moli 1 mol
O2 -----------------> O2 netransformat
1 1
a + a/2 + 1 = 5 /*2
=> 2a+a+2 = 10
=> a = 8/3 = 2,667 moli
=> initial = amestec 2,667 moli H2 + 2,333 moli O2
%H2 = 2,667x100/5 = 53,33% H2
%O = 100 - 53,33 = 46,67% O2