Physics question calculate the energy required to vaporise 50kg of water initially at 80c
raise it from 80 to 100 C heat energy in = C m (100 - 80)
C = specific heat of water
m = mass (watch units of C, probably use 50,000 grams)
vaporise it. heat energy in = K m
K = heat of vaporization of water
add those two energies
To calculate the energy required to vaporize water, you can use the formula:
Q = m * ΔHv
where:
Q is the energy required (in joules),
m is the mass of water (in kilograms),
ΔHv is the heat of vaporization of water (in joules per kilogram).
The heat of vaporization of water is 2,260,000 J/kg.
Let's plug in the values into the formula:
Q = 50 kg * 2,260,000 J/kg
Q = 113,000,000 J or 113 megajoules (MJ)
Therefore, it would require approximately 113 megajoules of energy to vaporize 50 kg of water initially at 80 °C.
To calculate the energy required to vaporize water, we need to consider three steps: raising the temperature of water from 80°C to its boiling point, vaporizing the water at its boiling point, and finally raising the temperature of vapor from the boiling point to the given temperature under standard atmospheric pressure.
Step 1: Raising the temperature of water from 80°C to its boiling point.
The specific heat capacity of water is approximately 4.18 J/g°C. Therefore, the energy required to raise the temperature of water from 80°C to its boiling point (100°C) can be calculated using the formula:
Energy = mass × specific heat capacity × change in temperature
Substituting the values:
Energy1 = 50 kg × 4.18 J/g°C × (100°C - 80°C)
Note: We convert the specific heat capacity from J/g°C to J/kg°C by dividing it by 1000.
Step 2: Vaporizing the water at its boiling point.
The specific heat of vaporization of water is approximately 2260 J/g. Therefore, the energy required to vaporize the water can be calculated using the formula:
Energy2 = mass × specific heat of vaporization
Substituting the values:
Energy2 = 50 kg × 2260 J/g
Step 3: Raising the temperature of the vapor from the boiling point to the given temperature under standard atmospheric pressure.
Since the vapor is already at 100°C, no additional energy is required to raise its temperature.
Finally, we can calculate the total energy required by summing up the energies from each step:
Total Energy = Energy1 + Energy2
Substituting the values and performing the calculations will give you the answer.