Question

The amount of energy released by burning a fuel source, measured in energy per mass, is called the fuel value. If all the energy obtained from burning 1.26 pounds of methane (fuel value is 11.97 kcal/g) is used to heat 123.5 kg of water at an initial temperature of 18.6 °C, what is the final temperature?

Answer 1

1.00 lbs = 453.592 g

1.26 lbs = 571.5264 g
Given that;

The fuel value of methane is 11.97 kcal/g

So 571.5264 x 11.97 kcal/g = 6841.17 kcal

No this kcal converted into KJ as follows:

1.0 Kcal = 4.184 KJ

6841.17 kcal = 28623.45528 kJ

This amount of energy is used to heat the 123.5 kg water as follows:

Q = mass *Cp* temperature change
28623.45528 kJ = 123.5 kg x 4.19 kJ/kgoC x Delta T

Delta t = 55.3 oC

If the initial temperature = 18.6 °C,

then the final temperature = 18.6 °C + 55.3 oC

= 73.9 oC