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Standard XII
Chemistry
Spontaneity
For a chemica...
Question

For a chemical reactions, the free energy change (ΔG) is negative. The reaction is

A
Spontaneous reaction
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B
An equilibrium reaction
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C
A non-spontaneous reaction
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D
Characterised by ri=rb (where, ri and rb are rates of forward and backward reactions respectively)
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Solution

The correct option is A Spontaneous reaction
For a spontaneous reaction, the free energy change ΔG should be negative.

ΔG<0

Hence, option A is correct.

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Q. Free energy, G=H−TΔS, is a state function that indicates 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, ΔG=ΔH−TΔS

From the second law of Thermodynamics, a reaction is spontaneous if ΔtotalS is positive, non-spontaneous if ΔtotalS is negative, and at equilibrium if ΔtotalS is zero.

Since, −TΔS=ΔG and since ΔG and ΔS have opposite signs, we can restate the Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure.
If ΔG<0, the reaction is spontaneous
If ΔG>0, the reaction is non-spontaneous
If ΔG=0, the reaction is at equilibrium

Read the above paragraph carefully and answer the following questions based on the above comprehension.

A particular reaction has a negative value for the free energy change. Then at ordinary temperature:

Q. Statement 1: For a chemical reaction at initial stage rate of forward reaction (rf) is greater than rate of reversed reaction (rb)
Statement 2: When rf=rb, chemical reaction is at equilibrium.
Q. Free energy, G=H−TΔS, is a state function that indicates 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, ΔG=ΔH−TΔS
From the second law of Thermodynamics, a reaction is spontaneous if ΔtotalS is positive, non-spontaneous if ΔtotalS is negative, and at equilibrium if ΔtotalS is zero.
Since, −TΔS=ΔG and since ΔG and ΔS have opposite signs, we can restate the Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure.
If ΔG<0, the reaction is spontaneous
If ΔG>0, the reaction is non-spontaneous
If ΔG=0, the reaction is at equilibrium
Read the above paragraph carefully and answer the following questions based on the above comprehension.
If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then:

Q. Free energy, G=H−TΔS, is a state function that indicates 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, ΔG=ΔH−TΔS
From the second law of Thermodynamics, a reaction is spontaneous if ΔtotalS is positive, non-spontaneous if ΔtotalS is negative, and at equilibrium if ΔtotalS is zero.
Since, −TΔS=ΔG and since ΔG and ΔS have opposite signs, we can restate the Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure.
If ΔG<0, the reaction is spontaneous
If ΔG>0, the reaction is non-spontaneous
If ΔG=0, the reaction is at equilibrium
Read the above paragraph carefully and answer the following questions based on the above comprehension.
One mol of ice is converted to liquid at 273K; H2O(s) and H2O(l) have entropies 38.20 and 60.03Jmol−1dg−1. Enthalpy change in the conversion will be:

Q. For a reaction to be spontaneous, the sign of Gibbs Free Energy change ΔG is ________.
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