Given: Volume of "H"_2H2 at STP; PP and TT of "HCl"HCl; chemical equation (understood)
Find: Volume of "HCl"HCl
Strategy:
The central part of any stoichiometry problem is to convert moles of something to moles of something else.
(a) We start with the balanced chemical equation for the reaction.
(b) We can use the molar ratio from the equation to convert moles of "H"_2H2 to moles of "HCl"HCl.
"moles of H"_2stackrelcolor (blue)("molar ratio"color(white)(Xl))( →) "moles of HCl"moles of H2molar ratioXl−−−−−−−→moles of HCl
(c) We can use the Ideal Gas Law (IGL) to convert the volume of "H"_2H2 to moles of "H"_2H2.
(d) We can also use the IGL to convert moles of "HCl"HCl to volume of "HCl"HCl.
Our complete strategy is:
"Volume of H"_2stackrelcolor (blue)("IGL"color(white)(Xl))(→) "moles of H"_2stackrelcolor (blue)("molar ratio"color(white)(Xl))( →) "moles of HCl"stackrelcolor (blue)( "IGL"color(white)(Xl))(→)"Volume of HCl"Volume of H2IGLXl−−−→moles of H2molar ratioXl−−−−−−−→moles of HClIGLXl−−−→Volume of HCl
Solution
(a) The balanced equation is
"H"_2 + "Cl"_2 → "2HCl"H2+Cl2→2HCl
(b) Calculate moles of "H"_2H2
STP is defined as 10^5color(white)(l) "Pa"105lPa and "273.15 K"273.15 K.
PV = nRTPV=nRT
n = (PV)/(RT) = (10^5 color(red)(cancel(color(black)("Pa"))) × 1150 color(red)(cancel(color(black)("m"^3))))/(8.314 color(red)(cancel(color(black)("Pa·m"^3"K"^(-1))))"mol"^(-1) × 273.15 color(red)(cancel(color(black)("K")))) = "50 640 mol"
(c) Calculate moles of "HCl"
The molar ratio of "HCl to H"_2 is "2 mol HCl"/("1 mol H"_2)"
"Moles of HCl" = 50 640 color(red)(cancel(color(black)("mol H"_2))) × "2 mol HCl"/(1 color(red)(cancel(color(black)("mol H"_2)))) = "101 280 mol HCl"
(d) Calculate the volume of "HCl"
105 color(red)(cancel(color(black)("kPa"))) × "1000 Pa"/(1 color(red)(cancel(color(black)("kPa")))) = "105 000 Pa"
PV = nRT
V= (nRT)/P = ("101 280" color(red)(cancel(color(black)("mol"))) × 8.314 color(red)(cancel(color(black)("Pa")))"·m"^3color(red)(cancel(color(black)("K"^(-1)"mol"^(-1)))) × 296 color(red)(cancel(color(black)("K"))))/("105 000" color(red)(cancel(color(black)("Pa")))) = "2370 m"^3
(3 significant figures)
Answer: The reaction will form "2370 m"^3 of "HCl".