Home
Class 11
CHEMISTRY
Statement-1: At low temperatures, DH is ...

Statement-1: At low temperatures, DH is the dominant factor for spontaneity of a reaction.
Statement-2: At low temperatures, the opposing factor TDS remains very small.

A

Statement-1 is true, Statement-2, is true, Statement -2 is a correct explanation for statement-1

B

Statement-1 is true, Statement-2, is true, Statement -2 is not a correct explanation for statement-1

C

Statement-1 is true, Statement-2 is false

D

Statement-1 is false, Statement-2 is true

Text Solution

Verified by Experts

The correct Answer is:
A
Promotional Banner

Topper's Solved these Questions

  • THERMODYNAMICS

    NARAYNA|Exercise Level-VI|150 Videos

  • THERMODYNAMICS

    NARAYNA|Exercise Passages|13 Videos

  • THERMODYNAMICS

    NARAYNA|Exercise Level-II (H.W)|24 Videos

  • STRUCTURE OF ATOM

    NARAYNA|Exercise EXERCISE - IV EXEMPLAR PROBLEMS|24 Videos

Similar Questions

Explore conceptually related problems

At very low temperature, ice condenses to ________ form.

Statement-1 : At low pressure and high temperature real gas approaches the ideal gas behaviour. and Statement-2 : At low prossure and high temperature the molecules are negligible.

Which of the following reactions is spontaneous only at reletively low temperature?

What are the sign of DeltaH and DeltaS for a reaction that is spontaneous only at low temperatures?

Statement-I: The temperature on the surface of planet Earth is neither too low nor too high. Statement-II: Atmosphere is not present on Earth

Low temperature is favourable for ……….. reactions.

Dependence of Spontaneity on Temperature: For a process to be spontaneous , at constant temperature and pressure , there must be decrease in free energy of the system in the direction of the process , i.e. DeltaG_(P.T) lt 0. DeltaG_(P.T) =0 implies the equilibrium condition and DeltaG_(P.T) gt 0 corresponds to non- spontaneity. Gibbs- Helmholtz equation relates the free energy change to the enthalpy and entropy changes of the process as : " "DeltaG_(P.T) = DeltaH-TDeltaS" ""..."(1) The magnitude of DeltaH does not change much with the change in temperature but the entropy factor TDeltaS change appreciably . Thus, spontaneity of a process depends very much on temperature. For endothermic process, both DeltaH and DeltaS are positive . The energy factor, the first factor of equation, opposes the spontaneity whereas entorpy factor favours it. At low temperature the favourable factor TDeltaS will be small and may be less than DeltaH, DeltaG will have positive value indicated the nonspontaneity of the process. On raising temperature , the factor TDeltaS Increases appreciably and when it exceeds DeltaH, DeltaG would become negative and the process would be spontaneous . For an expthermic process, both DeltaH and DeltaS would be negative . In this case the first factor of eq.1 favours the spontaneity whereas the second factor opposes it. At high temperature , when T DeltaS gt DeltaH, DeltaG will have positive value, showing thereby the non-spontaneity fo the process . However , on decreasing temperature , the factor , TDeltaS decreases rapidly and when TDeltaS lt DeltaH, DeltaG becomes negative and the process occurs spontaneously. Thus , an exothermic process may be spontaneous at low temperature and non-spontaneous at high temperature. For the reaction at 298 K ,2A + B rarr C DeltaH =100 kcal and DeltaS=0.050 kcal K^(-1) . If DeltaH and DeltaS are assumed to be constant over the temperature range, above what temperature will the reaction become spontaneous?

Dependence of Spontaneity on Temperature: For a process to be spontaneous , at constant temperature and pressure , there must be decrease in free energy of the system in the direction of the process , i.e. DeltaG_(P.T) lt 0. DeltaG_(P.T) =0 implies the equilibrium condition and DeltaG_(P.T) gt 0 corresponds to non- spontaneity. Gibbs- Helmholtz equation relates the free energy change to the enthalpy and entropy changes of the process as : " "DeltaG_(P.T) = DeltaH-TDeltaS" ""..."(1) The magnitude of DeltaH does not change much with the change in temperature but the entropy factor TDeltaS change appreciably . Thus, spontaneity of a process depends very much on temperature. For endothermic process, both DeltaH and DeltaS are positive . The energy factor, the first factor of equation, opposes the spontaneity whereas entorpy factor favours it. At low temperature the favourable factor TDeltaS will be small and may be less than DeltaH, DeltaG will have positive value indicated the nonspontaneity of the process. On raising temperature , the factor TDeltaS Increases appreciably and when it exceeds DeltaH, DeltaG would become negative and the process would be spontaneous . For an expthermic process, both DeltaH and DeltaS would be negative . In this case the first factor of eq.1 favours the spontaneity whereas the second factor opposes it. At high temperature , when T DeltaS gt DeltaH, DeltaG will have positive value, showing thereby the non-spontaneity fo the process . However , on decreasing temperature , the factor , TDeltaS decreases rapidly and when TDeltaS lt DeltaH, DeltaG becomes negative and the process occurs spontaneously. Thus , an exothermic process may be spontaneous at low temperature and non-spontaneous at high temperature. For the reaction at 25^(@), X_(2)O_(4)(l) rarr 2XO_(2)(g) DeltaH=2.1 Kcal and DeltaS = 20 cal K^(-1) . The reaction would be

Dependence of Spontaneity on Temperature: For a process to be spontaneous , at constant temperature and pressure , there must be decrease in free energy of the system in the direction of the process , i.e. DeltaG_(P.T) lt 0. DeltaG_(P.T) =0 implies the equilibrium condition and DeltaG_(P.T) gt 0 corresponds to non- spontaneity. Gibbs- Helmholtz equation relates the free energy change to the enthalpy and entropy changes of the process as : " "DeltaG_(P.T) = DeltaH-TDeltaS" ""..."(1) The magnitude of DeltaH does not change much with the change in temperature but the entropy factor TDeltaS change appreciably . Thus, spontaneity of a process depends very much on temperature. For endothermic process, both DeltaH and DeltaS are positive . The energy factor, the first factor of equation, opposes the spontaneity whereas entorpy factor favours it. At low temperature the favourable factor TDeltaS will be small and may be less than DeltaH, DeltaG will have positive value indicated the nonspontaneity of the process. On raising temperature , the factor TDeltaS Increases appreciably and when it exceeds DeltaH, DeltaG would become negative and the process would be spontaneous . For an expthermic process, both DeltaH and DeltaS would be negative . In this case the first factor of eq.1 favours the spontaneity whereas the second factor opposes it. At high temperature , when T DeltaS gt DeltaH, DeltaG will have positive value, showing thereby the non-spontaneity fo the process . However , on decreasing temperature , the factor , TDeltaS decreases rapidly and when TDeltaS lt DeltaH, DeltaG becomes negative and the process occurs spontaneously. Thus , an exothermic process may be spontaneous at low temperature and non-spontaneous at high temperature. A reaction has a value of DeltaH =-40 Kcal at 400 k cal mol^(-1) . The reaction is spontaneous, below this temperature , it is not . The values fo DeltaG and DeltaS at 400 k are respectively

NARAYNA-THERMODYNAMICS-Level -V
  1. Staetement -1: The magniyude of the work involed in an isothermal expa...

    Text Solution

    |

  2. Statement -1: For every chmical reaction at equilibrium , standard Gid...

    Text Solution

    |

  3. Statement-1: There is a natural asymmetry between work to heat and con...

    Text Solution

    |

  4. Statement -1: Entropy change in reversible adiabatic expansion of an i...

    Text Solution

    |

  5. Statement -1: The Standard free energy changes of all spontaneously oc...

    Text Solution

    |

  6. Statement -1: Enthalpy and entropy of any elements substance in the st...

    Text Solution

    |

  7. Statement-1: A reaction which is spontaneous and accompained by decrea...

    Text Solution

    |

  8. Statement -1: Many endothermic reactions that are not spontaneous at r...

    Text Solution

    |

  9. Statement-1: Decrease of free energy during the process under constant...

    Text Solution

    |

  10. Statement-1: All combustion reactions are exothermic. Statement-2: E...

    Text Solution

    |

  11. Statement-1: Due to adiabatic free expansion temperature of real gas m...

    Text Solution

    |

  12. Statement-1: Under adiabatic free expansion, ((dU)/(dV))(T) is +ve whe...

    Text Solution

    |

  13. Statement-1: At low temperatures, DH is the dominant factor for sponta...

    Text Solution

    |

  14. Statement-1: A reaction which is spontaneous and accompained by decrea...

    Text Solution

    |

  15. The temperature of 1 mole helium gas is increased by 1^@C. Find the in...

    Text Solution

    |

  16. An ideal gas is taken through the cycle A rarr B rarr C rarr A As show...

    Text Solution

    |

  17. If 2kcal heat is given to a system and 6 kcal work is done on the syst...

    Text Solution

    |

  18. The constant volume molar heat capacity of an ideal gas is expressed b...

    Text Solution

    |

  19. Molar enthalpy of vaporization of a liquid is 2.6 kJ. If boiling point...

    Text Solution

    |

  20. The chemical reaction : A rarr P, Delta H^(@) = 2.8 kJ is spontaneous ...

    Text Solution

    |