thank you mr teo... i just answered one question.. but i need somebody to correct me.. sory for my bad english(im trying so hard with it)
Pure oxygen gas was first prepared by heating mercury(II) oxide, HgO:
2 HgO(s) → 2 Hg(l) + O2(g)
What volume (in liters) of oxygen at STP is released by heating 10.57g of
HgO?
answer
mol HgO react to produce 1 mol O2
Mol of HgO = 10.57 g / 216.59 g/mol
= 0.0488
...mol
If 2
mol HgO react to produce 1 mol
O2
0.0488 mol HgO will produce 0.0244 mol O2
At STP
1 mol of gas will occupied 22.4 L
If 0.0244 mol O2 will occupied 0.5466
L
Volume O2 produce = 0.5466 L