Liquid nitrogen, which has a boiling point of −195.79°C, is used as a coolant and as a preservative for biological tissues. Is the entropy of nitrogen higher or lower at −200°C than at −190°C? Explain your answer. Liquid nitrogen freezes to a white solid at −210.00°C, with an enthalpy of fusion of 0.71 kJ/mol. What is its entropy of fusion? Is freezing biological tissue in liquid nitrogen an example of a reversible process or an irreversible process?

Explanation:

Entropy is measure of disorder so as we lower the temperature of gas , its entropy decreases .

Hence at - 200°C entropy of nitrogen will be less than that at - 190°C .

At freezing point ,

entropy of fusion  = latent heat / freezing temperature

= .71 kJ / ( 273 - 210 )

= 710 / 63 J mol⁻¹ K⁻¹ .

= 11.27 J mol⁻¹ K⁻¹ .

entropy of fusion = 11.27 J mol⁻¹ K⁻¹ .

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metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

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