Question

Calculate the mass of methane that must be burned to provide enough heat to convert 113.0 g of water at 19.0°C into steam at 125.0°C. (Assume that the H2O produced in the combustion reaction is steam rather than liquid water.)

Answer 1

Temperature difference is (125 - 19) = 106 C.

Energy needed to raise the temperature of 113 gms by 106 degrees will be

Q = m*s*t
Q ---is heat energy
m---- is the mass of water
s---is the specific heat (of H2O 4.2 J/g˚C)
t---- is the temperature difference.

=> Q = 119 * 4.2 * 106
=> Q = 52979

Now methane liberates 55 kJ of heat energy per gram.

So, methane required will be
52979/55 = 963.3 grams