Final answer:
The heat lost when 50 mL of water cools from 80°C to 21°C is -12.321 kJ, indicating that heat is released as the water cools.
Step-by-step explanation:
To calculate the heat lost when 50 mL (or 50 g) of water cools from 80°C to 21°C, we use the formula Q = m × c × ΔT, where Q is the heat transferred, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature. The specific heat capacity of water is 4.18 J/g°C.
Applying the formula:
- m = 50 g (since 1 mL of water is approximately equal to 1 g)
- c = 4.18 J/g°C
- ΔT = (21°C - 80°C) = -59°C
The negative sign indicates a release of heat as the water cools. Now, we calculate:
Q = 50×4.18×(-59)
Q = -12,321 J, which is a release of heat.
Converting joules to kilojoules: Q = -12.321 kJ (since 1 kJ = 1000 J).