For the combustion reaction 4"NH"_3(g) + 5"O"_2(g) -> 4"NO"(g) + 6"H"_2"O"(g)4NH3(g)+5O2(g)→4NO(g)+6H2O(g), how many liters of "O"_2(g)O2(g) would react with "500 L"500 L of "NH"_3NH3 at STP?
1 Answer
"625 L O"_2625 L O2
This is a limiting reactant problem using gases (assumed ideal).
Given
PV = nRTPV=nRT
V/n = (RT)/PVn=RTP
= (("0.082057 L"cdotcancel"atm""/mol"cdotcancel"K")(273.15 cancel"K"))/(cancel"1 atm")
= "22.41 L/mol"
Therefore, we have
500 cancel("L NH"_3) xx "1 mol"/(22.41 cancel("L NH"_3(g)))
= "22.31 mols NH"_3
From the reaction given, there needs to be
22.31 cancel("mols NH"_3) xx ("5 mols O"_2)/(4 cancel("mols NH"_3))
= "27.88 mols O"_2
Since we are also assuming
27.88 cancel("mols O"_2(g)) xx "22.41 L"/cancel("mol O"_2(g))
= color(blue)("625 L O"_2(g))
You could also have gone straight from the volume and used the mol ratio by ASSUMING that both
"500 L" cancel("NH"_3) xx (5 cancel"mols" "O"_2)/(4 cancel"mols" cancel("NH"_3))
= color(blue)("625 L O"_2(g))