CBSE Guess > Papers > Important Questions > Class XII > 2007 > Chemistry > Thermodoynamics

Thermodoynamics

1. State 3rd law of thermodynamics. Explain its’ implications
2. Place the following systems in order of increasing randomness.
   a) 1 mole of gas X.
   b) 1 mole of solid X.
   c) 1 mole of liquid X.
3. Why would you expect a decrease in entropy as a gas condenses into liquid? Compare it with entropy decrease when a liquid sample is converted into solid.
4. Which of the following processes are accompanied by increase in entropy.
   a) Dissolution of iodine in a solvent.
   b) HCl is added to AgNO3 and a ppt of AgCl is obtained.
   c) A partition is removed to allow two gases to mix.
5. Comment on the following statements.
   a) An exothermic reaction is always thermodynamically spontaneous.
   b) The entropy of a substance increases on going from the liquid to the vapour state at any temperature.
6. The enthalpy of vaporization of liquid diethyl ether [(C₂H₅)₂O] is 26 kJ/mol at 35⁰C. Calculate ∆S for conversion of Liquid to vapour
7. For the water gas reaction
   C(s) + H₂O(g) --> CO(g) + H₂(g)
   The standard Gibb’s free energy of reaction (at 1000k) is -8.1 kJmol ^-1. Callculate the equilibrium constant.
8. The standard Gibb’s energy is for the reaction at 1773K are given below.
   C + O₂ --> CO₂ , DG = -380KJ/mol
   2C + O₂ = 2CO DG = -120KJ/mol
   Discuss the possibility of reducing Al₂O₃ and PbO with carbon at this temperature.
   4Al + 3O₂ --> 2Al₂O₃, ∆G = -22500KJ/mol
   2Pb+O₂ --> 2PbO , ∆G = -120KJ/mol
9. How is concept of coupling of reaction useful in explaining the occurrence of a non-spontaneous reaction?
10. Sodium carbonate can be obtained by heating sodium hydrogen carbonate
    2NaHCO₃ --> Na₂CO₃ + H₂O + CO₂
    Calculate the temperature above which NaHCO₃ decomposes to form product at 1bar.

1. Atomic Structure and Chemical Bonding
2. Solid States
3. Solutions
4. Thermodoynamics
5. Chemical Kinetics
6. Nuclear Chemistry
7. Polymers
8. Biomolecules
9. Chemistry In Every Day Life