Anybody up for a stoichiometric challenge?

Question

If 6.214x10^24 molecules of P2S5 reacts with 16.4 grams of H20 and 4 moles of O2, what masses of phosphoric and sulfuric acid will be formed?(need balanced eq also)

If only 12 grams of phsphoric acid are formed, what is the percent yield? How many grams of each excess reactant are leftover?

Answer 1

The balanced equation is:
1 P2S5 + 8 H2O + 10 O2 --> 5 H2SO4 + 2 H3PO4

Now you need to find how many moles of each reactant:
6.214*10^24 molecules P2S5 /6.022*10^23 molecules/mole = 10.3 moles P2S5
16.4 g H20 / 18 g/mole = 0.91 mole H20
4 mole O2 given

Next, find which reactant will run out first , or the limiting reagent.
P2S5:H2O:O2 = 1:8:10
We need 1 mole of P2S5 for every 10 moles of O2 that react, so for 4 moles of O2, we would only need 0.4 moles. We have 10.3, so we have excess P2S5.
We need 8 moles of H2O for every 10 moles of O2, so for 0.91 moles H2O, we would need 1.274 moles O2. So we're limited by the amount of H2O.

For every 8 moles of H2O that react, we get 5 H2SO4 and 2 H3PO4. For only 0.91 moles, we would get 0.57 mole H2SO4 and 0.23 mole H3PO4.

H2SO4 has a molecular weight of 98 g/mole and H3PO4 is also 98 g/mole. SO, we would get 55.9g H2SO4 and 22.5g H3PO4.

If we only had 12 g of phosphoric acid, the percent yield would be 12/22.5 = 53%.

Answer 2

1P2S5 +7H2O + 20O2 ----> 2H2PO4 + 5H2SO4


And no way in hell am I trying the stoichiometry part...srry, but ther is the balnced egaution

Answer 3

dude screw this