Answer to Question #62178 in General Chemistry for Anthony

Question

A cup of coffee (140g) cools from 75c down to room temp of 20c. How much energy does it release to its surroundings?

Answer 1

Q = C×m×(T2-T1)
m = 140g;
T2 = 20C = 293K;
T1 = 75C = 348K;
We pretend, that coffee consists mostly of the water, so the specific heat capacity will be C= 4.18 J/(g×K)
Q = 4.18 × 140 × (293-348) = -32186 (J) = -32.2 (kJ)
Answer: The coffee transfers 32.2 kJ of energy to the surroundings, when it cools from 75C to 20C.