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Assertion(A) : When sodium chloride diss...

Assertion(A) : When sodium chloride dissolves in water, then `Na^(+)` and `Cl^(-)` ions leaving the crystal lattice acquire far greater freedon.
Reason(R ) : In thermodynamic terms, the formation of solution occurs with a favourable change in energy i.e., `DeltaH` has a high positive value and `TDeltaS` has a low negative value.

A

If both assertion and reason are true and reason is the correct explanation of assertion

B

If both assertion and reason are true but reason is not the correct explanation of assertion

C

If assertion is true but reasonb is false

D

If both assertion and reason are false.

Text Solution

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To solve the question, we need to analyze both the assertion (A) and the reason (R) provided. ### Step 1: Analyze the Assertion (A) The assertion states that when sodium chloride (NaCl) dissolves in water, the Na⁺ and Cl⁻ ions leave the crystal lattice and acquire greater freedom. **Explanation**: - Sodium chloride is an ionic compound that forms a crystal lattice structure. When it dissolves in water, the ionic bonds between Na⁺ and Cl⁻ ions are broken, allowing these ions to disperse throughout the solution. - This process indeed results in the ions having greater freedom of movement compared to when they are in the solid state. ### Step 2: Analyze the Reason (R) The reason states that in thermodynamic terms, the formation of the solution occurs with a favorable change in energy, i.e., ΔH has a high positive value and TΔS has a low negative value. **Explanation**: - In thermodynamics, the Gibbs free energy change (ΔG) is given by the equation: ΔG = ΔH - TΔS. - For a process to be spontaneous, ΔG must be negative. This typically requires ΔH to be negative (exothermic reaction) and ΔS to be positive (increase in entropy). - The reason provided states that ΔH has a high positive value, which implies that the process is endothermic, and TΔS has a low negative value, which does not support spontaneity. Therefore, the conditions described in the reason do not lead to a spontaneous process. ### Conclusion - The assertion (A) is **true** because the ions do acquire greater freedom when NaCl dissolves in water. - The reason (R) is **false** because the conditions described do not support a spontaneous process. ### Final Answer The correct answer is that the assertion is true, but the reason is false.
To solve the question, we need to analyze both the assertion (A) and the reason (R) provided. ### Step 1: Analyze the Assertion (A) The assertion states that when sodium chloride (NaCl) dissolves in water, the Na⁺ and Cl⁻ ions leave the crystal lattice and acquire greater freedom. **Explanation**: - Sodium chloride is an ionic compound that forms a crystal lattice structure. When it dissolves in water, the ionic bonds between Na⁺ and Cl⁻ ions are broken, allowing these ions to disperse throughout the solution. - This process indeed results in the ions having greater freedom of movement compared to when they are in the solid state. ...
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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

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. The enthalpy change for a certain rection at 300 K is -15.0 K cal mol^(-1) . The entropy change under these conditions is -7.2 cal K^(-1)mol^(-1) . The free energy change for the reaction and its spontaneous/ non-spontaneous character will be

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Free energy, G=H-TS, is a state function that includes whether a reaction is spontaneous or non-spontaneous. If you think of TS as the part of the system's energy that is disordered already, then (H-TS) is the part of the system's energy that is still ordered and therefore free to cause spontaneous change by becoming disordered. Also, DeltaG=DeltaH-TDeltaS To see what this equation for free energy change has to do with spontaneity let us return to relationship. DeltaS_("total")=DeltaS_("sys")+DeltaS_("surr") = DeltaS + DeltaS_("surr") (It is generally understood that symbols without subscript refer to the system not the surroundings.) DeltaS_("surr")=-(DeltaH)/T , where DeltaH is the heat gained by then system at constant pressure. DeltaS_("total") = DeltaS -(DeltaH)/T rArr TDeltaH_("total")=DeltaH-TDeltaS rArr -TDeltaS_("total") =DeltaH-TDeltaS i.e. DeltaG=-TDeltaS_("total") From second law of thermodynamics, a reaction is spontaneous if DeltaS_("total") is positive, non-spontanous if DeltaS_("total") is negative and at equilibrium if DeltaS_("total") is zero. Since, -TDeltaS=DeltaG and since DeltaG and DeltaS have opposite signs, we can restate the thermodynamic criterion for the spontaneity of a reaction carried out at constant temperature and pressure. If DeltaG lt 0 , the reaction is spontaneous. If DeltaG gt 0 , the reaction is non-spontanous. If DeltaG=0 , the reaction is at equilibrium. In the equation, DeltaG=DeltaH-TDeltaS , temperature is a weighting factor that determine the relative importance of enthalpy contribution to DeltaG . Read the above paragraph carefully and answer the following questions based on above comprehension: If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then

Free energy, G=H-TS, is a state function that includes whether a reaction is spontaneous or non-spontaneous. If you think of TS as the part of the system's energy that is disordered already, then (H-TS) is the part of the system's energy that is still ordered and therefore free to cause spontaneous change by becoming disordered. Also, DeltaG=DeltaH-TDeltaS To see what this equation for free energy change has to do with spontaneity let us return to relationship. DeltaS_("total")=DeltaS_("sys")+DeltaS_("surr") = DeltaS + DeltaS_("surr") (It is generally understood that symbols without subscript refer to the system not the surroundings.) DeltaS_("surr")=-(DeltaH)/T , where DeltaH is the heat gained by then system at constant pressure. DeltaS_("total") = DeltaS -(DeltaH)/T rArr TDeltaH_("total")=DeltaH-TDeltaS rArr -TDeltaS_("total") =DeltaH-TDeltaS i.e. DeltaG=-TDeltaS_("total") From second law of thermodynamics, a reaction is spontaneous if DeltaS_("total") is positive, non-spontanous if DeltaS_("total") is negative and at equilibrium if DeltaS_("total") is zero. Since, -TDeltaS=DeltaG and since DeltaG and DeltaS have opposite signs, we can restate the thermodynamic criterion for the spontaneity of a reaction carried out at constant temperature and pressure. If DeltaG lt 0 , the reaction is spontaneous. If DeltaG gt 0 , the reaction is non-spontanous. If DeltaG=0 , the reaction is at equilibrium. In the equation, DeltaG=DeltaH-TDeltaS , temperature is a weighting factor that determine the relative importance of enthalpy contribution to DeltaG . Read the above paragraph carefully and answer the following questions based on above comprehension: One mole of ice is converted to liquid at 273 K, H_(2)O(s) and H_(2)O(l) have entropies 38.20 and 60.03 J "mol"^(-1) K^(-1) . Enthalpy change in the conversion will be:

Free energy, G=H-TS, is a state function that includes whether a reaction is spontaneous or non-spontaneous. If you think of TS as the part of the system's energy that is disordered already, then (H-TS) is the part of the system's energy that is still ordered and therefore free to cause spontaneous change by becoming disordered. Also, DeltaG=DeltaH-TDeltaS To see what this equation for free energy change has to do with spontaneity let us return to relationship. DeltaS_("total")=DeltaS_("sys")+DeltaS_("surr") = DeltaS + DeltaS_("surr") (It is generally understood that symbols without subscript refer to the system not the surroundings.) DeltaS_("surr")=-(DeltaH)/T , where DeltaH is the heat gained by then system at constant pressure. DeltaS_("total") = DeltaS -(DeltaH)/T rArr TDeltaH_("total")=DeltaH-TDeltaS rArr -TDeltaS_("total") =DeltaH-TDeltaS i.e. DeltaG=-TDeltaS_("total") From second law of thermodynamics, a reaction is spontaneous if DeltaS_("total") is positive, non-spontanous if DeltaS_("total") is negative and at equilibrium if DeltaS_("total") is zero. Since, -TDeltaS=DeltaG and since DeltaG and DeltaS have opposite signs, we can restate the thermodynamic criterion for the spontaneity of a reaction carried out at constant temperature and pressure. If DeltaG lt 0 , the reaction is spontaneous. If DeltaG gt 0 , the reaction is non-spontanous. If DeltaG=0 , the reaction is at equilibrium. In the equation, DeltaG=DeltaH-TDeltaS , temperature is a weighting factor that determine the relative importance of enthalpy contribution to DeltaG . Read the above paragraph carefully and answer the following questions based on above comprehension: For the spontaneity of a reaction, which statement is true?