Question

(HW5-27)

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 1.27 pounds of butane (fuel value is 10.85 kcal/g) is used to heat 127.5 kg of water at an initial temperature of 18.7 °C, what is the final temperature?

Answer 1

1.27 pounds of butane is grams is 576 g of butane (obtained from a unit convertor)

since its fuel value is 10.85 kcal/g we

The amount of energy released by burning 576 g of butane will be

10.86kcal/g x 576g = 6255.36 kcal

If this energy is used to heat 127.5 kg of water at an initial temperature of 18.7 ^oC

The final temperature can be calculated using the formula

Q=mcT

where "Q" is the heat transferred in an exchange, "m" is the mass of the substance being heated in grams, "c" is its "specific heat capacity," and "T" is its change in temperature.

m = 127.5 x 10³ g

c= 1cal/g.^oC

Q as calculated above is 6255.36 kcal

We will be calculating T in ^oC

6255.26 x 10³ cal = 127.5 x 10³g x 1 cal/g.^oC x T

T = 6255.26 x 10³ cal/127.5 x 10³g x 1 cal/g.^oC

T = 49.06 ^oC

Since T = 49.06 ^oC and the initial temperature was 18.7 ^oC. The final temperature will be

18.7 ^oC +49.06 ^oC = 67.76 ^oC