InterviewSolution
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InterviewSolution
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`1gm` water at `100^(@)C` is heated to convert into steam at `100^(@)C` at `1atm`. Find out chage in internal energy of water. It is given that volume of `1gm` water at `100^(@)C = 1c c`, volume of `1gm` steam at `100^(@)C = 167 1 c c`. Latent heat of vaporization `= 540 cal//g`. (Mechanical equivalent of heat `J = 4.2J//cal)` |
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Answer» 1 atmosphere `=1.013xx10^(5) Nm^(2)` : volume of 1 gm of water, `V_(1)=1 c c=10^(-6)m^(3)`, `(because rho =(m)/(V) & rho=1gm // c c)` Volume of steam `=1671 c c=1671xx10^(-6)m^(3)` External work doen `dW=P(V_(2)-V_(1))` `=1.013xx10^(5)(1671xx10^(-6)-1xx1-^(-6))` `=1.013xx10^(5)xx1670xx10^(-6)` `=1.013xx167=169.2J`. Latent heat of vaporisation of steam=540 cal/g So, heat supplied to convert 1g of water into steam, `DeltaQ=540xx4.2J=226.8J` By first law of thermodynamics `DeltaU=DeltaQ-DeltaW=2268-169.2=2098.8J` |
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