Question

Calculate the mass of methane that must be burned to provide enough heat to convert 359.0 g of water at 19.0°C into steam at 103.0°C. (Assume that the H₂O produced in the combustion reaction is steam rather than liquid water.)

Answer 1

First let us calculate the heat need to convert 359.0 g of water at 19.0°C into steam at 103.0°C

Q = m c ∆T
Q = quantity of heat in joules (J)
m = mass of the substance acting as the environment in
grams (g)
c = specific heat capacity (4.19 for H2O) in J/(g ^oC)

Q = 359 x 4.18 x (100-19) + 359 x 40700 /18 + 359 x 3 x 2.02

Q = 121550 + 811738 + 2175

Q = 935464 Joules or 935.464 Kj

methane

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)

ΔH = -890

Mass of methane that must be burned = 935.464 / 890 = 1.051 Moles

Hence 1.051 Moles of Methane need to combust