The correct option is B 4 g
The unbalanced eqauation is,
Ag2O→Ag+O2
1 mol of Ag2O contains 1 mol of O atoms;
1 mol of O2 contains 2 mol of O atoms.
Applying POAC on O atom,
1×mol of Ag2O=2×mole of O2
Moles of O2 = 0.5×moles of Ag2O
So, we can calculate the moles of Ag2O, convert it into the moles of O2 and finally to grams of O2.
Moles of Ag2O = 57.93231.73 = 0.25 mol
Moles of O2 = 0.125 mol
Mass of O2 = 0.125×32 = 4 g