Thermodynamics

Efficiency of Car not engine is given by,

%5Ceta%20%3D1-%5Cfrac%7B%7B%7BT%7D_%7B2%7D%7D%7D%7B%7B%7BT%7D_%7B1%7D%7D%7D

where

%7B%7B%5Ctext%7BT%7D%7D_%7B%5Ctext%7B2%7D%7D%7D

is temperature of sink in kelvin and

%7B%7B%5Ctext%7BT%7D%7D_%7B1%7D%7D

is temperature of source in kelvin. Given,

%5Ceta%20%3D25%25%3D%5Cfrac%7B25%7D%7B100%7D%3D0.25

%7B%7BT%7D_%7B2%7D%7D%3D27%7B%7B%5C%2C%7D%5E%7Bo%7D%7DC%3D27%2B273%3D300%5C%2CK

%5Ctherefore

0.25%3D1-%5Cfrac%7B300%7D%7B%7B%7BT%7D_%7B1%7D%7D%7D

%5CRightarrow

%5Cfrac%7B300%7D%7B%7B%7BT%7D_%7B1%7D%7D%7D%3D1-0.25

%5CRightarrow

%5Cfrac%7B300%7D%7B%7B%7BT%7D_%7B1%7D%7D%7D%3D0.75

%5CRightarrow

%7B%7BT%7D_%7B1%7D%7D%3D%5Cfrac%7B300%7D%7B0.75%7D%3D400%5C%2CK%3D127%5C%2C%7B%7B%5C%2C%7D%5E%7Bo%7D%7DC

Power consumed in electrolysis, P = 100 W Voltage applied, V=125V So, current in the solution,

i%3D%5Cfrac%7BP%7D%7BV%7D%3D%5Cfrac%7B100%7D%7B125%7D%3D0.8%5C%2C%5Ctext%7BA%7D

According to first law of Faraday, mass liberated at an electrode is directly proportional to charge passed through the electrolyte ie,

m%5Cpropto%20Q

%5CRightarrow

m%3Dz%5C%2CQ

where z is a constant called electro chemical equivalent (ECE). Also

Q%3Di%5C%2Ct

%5Ctherefore

m%3Dz%5C%2Cit

Given,

z%3D0.367%5Ctimes%20%7B%7B10%7D%5E%7B-6%7D%7Dkg%5C%2CC%2CI%3D0.8A%2Ct%3D60%5C%2Cs

Hence,

m%3D0.367%5Ctimes%20%7B%7B10%7D%5E%7B-6%7D%7D%5Ctimes%200.8%5Ctimes%2060

%3D17.6%5Ctimes%20%7B%7B10%7D%5E%7B-6%7D%7D%5C%2Ckg

%3D17.6%5C%2Cmg

Chapter Questions
2 MCQs