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भारतीय रसायन के पिता आचार्य प्रफुल्ल चंद्र रे की जयंती पर व्याख्यान का आयोजन

भारतीय रसायन के पिता आचार्य प्रफुल्ल चंद्र रे की जयंती पर व्याख्यान का आयोजन विज्ञान भारती उदयपुर इकाई एवं बीएन कॉलेज ऑफ फार्मेसी, बीएन विश्वविद्यालय के संयुक्त तत्वावधान में कार्यक्रम सम्पन्न उदयपुर, 2 अगस्त। भारतीय रसायन के पिता आचार्य प्रफुल्ल चंद्र रे की जयंती के अवसर पर विज्ञान भारती उदयपुर इकाई (चित्तौड़ प्रांत) एवं बीएन कॉलेज ऑफ फार्मेसी, बीएन विश्वविद्यालय के संयुक्त तत्वावधान में एक विशेष व्याख्यान का आयोजन किया गया। कार्यक्रम का उद्देश्य आचार्य पी.सी. रे के वैज्ञानिक योगदान एवं उनके देशभक्ति से ओतप्रोत जीवन पर प्रकाश डालना था। ज्ञातव्य है कि भारत की पहली फार्मा कंपनी आचार्य रे ने ही बंगाल केमिकल एंड फार्मास्यूटिकल्स लिमिटेड, कोलकाता में 1901 में प्रारंभ की थी। कार्यक्रम में विज्ञान भारती के उद्देश्य एवं गतिविधियों की जानकारी डॉ. अमित गुप्ता द्वारा दी गई। आचार्य पी.सी. रे के जीवन और कार्यों पर मुख्य व्याख्यान डॉ. लोकेश अग्रवाल द्वारा प्रस्तुत किया गया। उन्होंने बताया कि कैसे आचार्य रे ने विज्ञान को समाज की सेवा का माध्यम बनाया और रसायन विज्ञान में भारत को आत्मनिर्भर बनान...

Dulong and Petit's law

Dulong and Petit's law

  • According to Dulong and Petit's law the product of atomic weight and specific heat for all the elements in its solid state is always constant and its value is approximately 6.4. 
  • This law is used to determine the atomic weight of substance.

    Dulong and Petit’s law from Kinetic theory

  • According to the law of equi-partition of energy, the average kinetic energy of translation associated with each degree of freedom is 1/2kT.
  • If the oscillatory motion of atom is simple harmonic then in each oscillation the average kinetic energy = Average potential energy.
        Total energy associated with each degree of freedom of atom 
                                    = 1/2 kT + 1/2 kT = kT
        Since there are three degrees of freedom for oscillatory motion of each atom
        So the total energy of each atom = 3kT
        If we consider the 1 gm-atom of any solid at absolute temperature T
        So the number of atoms in 1 gm-atom of gas = N, where N is Avogadro number
        Total energy of 1 gm of solid
                  U = N * 3 kT = 3NkT                      [ R = Nk ]
                  U = 3RT
                 dU/dT = 3R
        Since dU/dT is the atomic heat of solid at constant volume i.e., Cv            
        So,    Cv = 3R
        Since R = 1.98 cal/gm-atom/°C
        So,    Cv = 3 * 1.98 = 5.94 cal/gm-atom/°C
        Atomic heat of solid = 6 cal cal/gm-atom/°C  (approximate)
       Thus it agrees with Dulong and Petit's law

Failure of Dulong and Petit's law

  • C, B, Si like non-metallic elements have value of atomic heat different from 6.4 at normal temperature (about 6.0).
  • But above 500°C their value tends to about 6.4.
  • At absolute zero temperature the value of atomic heat of all the elements tends to zero.
It is clear from the following figure


        Explanation of Failure of Dulong and Petit's law




To know about this lecture in more detail please visit on https://youtu.be/R_xEBgzUmkQ


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