Question

The heat of combustion of CH4 is 890.4 KJ/mol, and the heat capacity of H20 is 75.2 J/molK. Find the volume of methane measured at 298K and 1.00 atm required to convert 1.00L of water at 298 K to water vapor at 373K.

Answer 1

Q methane = Q water

Q = mcΔt

mass water = V x ρ = 1 L x 1 kg/L = 1 kg

298 K to 373K = 25 °C to 100 °C

c water = 75.2 J/mol K = 4.2 J / g °C = 4200 J/kg °C

Q water = 1 x 4200 x (100 - 25)

Q water = 315000 J

Q methane = Q water = 315000 J = 315 KJ

n (mol) methane = ΔH/Q = 890.4 / 315 = 2.83

PV = nRT

V = nRT/P

V = 2.83 x 0.082 x 298/1

V = 69.15 L