How much heat energy is released when a 500g sample of water vapor is cooled from 120°C to a final
temperature of -20°C?
To calculate the amount of heat energy released when a sample of water vapor is cooled, we need to use the specific heat capacity of water.
The specific heat capacity of water is 4.18 J/g°C.
First, we need to calculate the heat energy released when the water vapor is cooled from 120°C to 0°C.
Q = m * c * ΔT
Q = 500g * 4.18 J/g°C * (0°C - 120°C)
Q = -250,800 J
So, when the water vapor is cooled from 120°C to 0°C, 250,800 J of heat energy is released.
Next, we need to calculate the heat energy released when the water freezes from 0°C to -20°C.
Q = m * c * ΔT
Q = 500g * 2.09 J/g°C * (0°C - (-20°C))
Q = -20,900 J
So, when the water freezes from 0°C to -20°C, an additional 20,900 J of heat energy is released.
Therefore, the total amount of heat energy released when the 500g sample of water vapor is cooled from 120°C to a final temperature of -20°C is 250,800 J + 20,900 J = 271,700 J.