Question

The heat of combustion of wood is approximately 16 kJ/g. What is the final temperature that 500.0 mL of water, initially at 25.0°C, will reach in a bomb calorimeter if 1.20 g of wood is burned?
a. 9.2 °C
b. 34.2 °C
c. 186 °C
d. No right answer.

Answer 1

Answer:

The final temperature is 34,2 ºC when 1,20 g of wood is burned inside the calorimeter.

Explanation:

The heat of combustion of wood which is approximately 16 kJ/g means that 1 g requires 16 kJ of heat so let's calculate about 1,20 g which is the value of wood you have.

1 g ________ 16 kJ

1,20 g ______ 1,20 g x 16 kJ = 19,2 kJ = 19200 J

Now let's apply the calorimetry formula

Q = m . C . ΔT

19200 J = 500 g . 4,186 J/ gºC ( Tfinal - 25ºC)

Look that we don't have the mass of water, instead we have the volume so as you know water density is 1 g/ml, we conclude that in 500 ml, we have 500 g.

On the other hand we convert the 19.2 kJ into J (* 1000) by the units in the value of the specific heat of the water, it is in Joule

19200 J = 500 g . 4,186 J/ gºC ( Tfinal - 25ºC)

19200 J = 2093 J/ºC ( Tfinal - 25ºC)

19200 J = 2093 J/ºC .Tfinal - 52,325 J

19200 J + 52325 J = 2, 093 J/ºC .Tfinal

71525 J = 2093 J/ºC .Tfinal

71525 J /2093 ºC / J = Tfinal = 34,17ºC