Question

How much energy, in joules, is released when 17 kilograms of granite is cooled from 45°C to 21°C?

A. 327,992.8 J
  B. 365,575.3 J
  C. 901,980.3 J
  D. 785,662.8 J

Answer 1

The awnser is b i think.

Answer 2

Energy or heat can be calculated in terms of the mass, temperature, and specific heat of a substance. This is given by the equation:

U = mCpΔT = mCp(Tf-Ti)

where:
m = mass
Cp = specific heat
ΔT = temperature difference

For this problem, you need to get the specific heat of granite which can be found in reliable chemistry/engineering books or websites. According to Engineering Toolbox website, the Cp of granite is 790 J/(kg-°C).

U = 17 kg (790 J/(kg-°C)) (21-45) = - 322,320 Joules

*Note: the sign is negative because energy was released