Apr 15th 2017, 05:16 AM
Join Date: Apr 2017
Application of First law of Thermodynamics
I was stuck on this problem and needed some assistance. I have provided the question and answer below.
Q. The specific latent heat of vaporisation of steam is 2.26 MJ/kg. When 50 cm^3 of water is boiled at standard atmospheric pressure of 1.01*10^5 Pa, 83*10^3 cm^3 of steam are formed.
Density of water = 1000 kg/m^3
1. Calculate the mass of water boiled.
Answer: 50*10^-3 KG.
So I know that the molecules have to do work against the atmospheric pressure to create the increased volume. Therefore, the work done is equal to the pressure multiplied the difference in final volume and the initial volume.
W = PdV = (1.01*10^-5)(0.083-5*10^-5) = 8377.95 J
Then I thought of using q = ml, but that wouldn't make sense because the calculated quantity above is not the energy required to change phase from water into steam?
I'm a bit confused and would appreciate any sort of help! Thank you in advance.