Calculate the energy required to vapourise 50g of water Initially at 80¡ãC if the specific heat capacity of water is 4.2 J/g.k. (specific latent heat of vapourisation of water is 2260 J/g)
I still don't understand.
To calculate the energy required to vaporize 50g of water, you need to consider two steps: the energy required to raise the temperature of the water from 80°C to its boiling point, and the energy required for the phase change from liquid to vapor.
Step 1: Calculating the energy required to raise the temperature from 80°C to boiling point
The specific heat capacity of water is given as 4.2 J/g·K. This means that it takes 4.2 Joules of energy to raise the temperature of 1 gram of water by 1 degree Celsius.
To calculate the energy required to raise the temperature of 50g of water from 80°C to its boiling point, you can use the formula:
Q = m × c × ΔT
where:
Q = energy (in Joules)
m = mass of water (in grams)
c = specific heat capacity of water (in J/g·K)
ΔT = change in temperature (in °C)
Plugging in the given values:
m = 50g
c = 4.2 J/g·K
ΔT = (boiling point of water - initial temperature) = (100°C - 80°C) = 20°C
Q = 50g × 4.2 J/g·K × 20°C = 4200 J
So, the energy required to raise the temperature of water from 80°C to its boiling point is 4200 Joules.
Step 2: Calculating the energy required for the phase change from liquid to vaporization
The specific latent heat of vaporization of water is given as 2260 J/g. This means that it takes 2260 Joules of energy to convert 1 gram of water from a liquid to a gas at its boiling point.
To calculate the energy required to vaporize 50g of water, you can use the formula:
Q = m × L
where:
Q = energy (in Joules)
m = mass of water (in grams)
L = specific latent heat of vaporization of water (in J/g)
Plugging in the given values:
m = 50g
L = 2260 J/g
Q = 50g × 2260 J/g = 113,000 J
So, the energy required to vaporize 50g of water is 113,000 Joules.
Adding up the energy required for both steps:
Total energy required = Energy to raise the temperature + Energy for phase change
= 4200 J + 113,000 J
= 117,200 J
Therefore, the energy required to vaporize 50g of water initially at 80°C is 117,200 Joules.