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 1.20 pounds of propane (fuel value is 11.09 kcal/g) is used to heat 129.0 kg of water at an initial temperature of 19.8 °C, what is the final temperature?

Answer 1

Given fuel value of propane is 11.09 kcal/g

mass of propane = 1.20 pound x(453.6 g / pound) = 544.32 g

For 1g of propane the heat released is 11.09 kcal

For 544.32 g of propane the heat released is (544.32 x 11.09 ) / 1 kcal = 6036.5 kcal (=Q)

This amount of heat was absorbed by water and Q = mcdt

Where

m = mass of water = 129.0 kg = 129x1000 g

c = specific heat capacity of water = 0.239 cal/g oC

dt = change in temperature = final - initial = ( t-19.8) oC

Plug the values we get

Q = mcdt

6036.5 kcal x ( 1000 cal / kcal) = 129x1000 g x 0.239 (cal/g oC) x ( t-19.8)

( t-19.8) = 195.9 oC

t = 215.7 oC

Therefore the final temperature of water is  215.7 oC