Question

for for a reaction both ∆H and T∆S are positive. under what condition does the reaction occurs spontaneously.??​

Answer 1

Answer:

∆H = -ve ...

T∆S = +ve..

We know That ...

∆G = ∆H -- T∆S...

For a reaction to be spontaneous....

∆G = -ve

So....T∆S > ∆H

and so....The temperature should be high......

Answer 2

Answer:

In order to any reaction to be spontaneous ΔG must have negative value.

i..e. If ΔH and ΔS are positive then..

TΔS>ΔH

Explanation:

In a practical and frequently used form of Gibbs free energy change equation, ΔG is calculated from a set values that can be measured by scientists: the enthalpy and entropy changes of a reaction, together with the temperature at which the reaction takes place.

ΔG=ΔH−TΔS

Let’s take a step back and look at each component of this equation.

• ∆H is the enthalpy change. Enthalpy in biology refers to energy stored in bonds, and the change in enthalpy is the difference in bond energies between the products and the reactants. A negative ∆H means heat is released in going from reactants to products, while a positive ∆H means heat is absorbed. (This interpretation of ∆H assumes constant pressure, which is a reasonable assumption inside a living cell).
• ∆S is the entropy change of the system during the reaction. If ∆S is positive, the system becomes more disordered during the reaction (for instance, when one large molecule splits into several smaller ones). If ∆S is negative, it means the system becomes more ordered.
• Temperature (T) determines the relative impacts of the ∆S and ∆H terms on the overall free energy change of the reaction. (The higher the temperature, the greater the impact of the ∆S term relative to the ∆H term.) Note that temperature needs to be in Kelvin (K) here for the equation to work properly.
• Reactions with a negative ∆G release energy, which means that they can proceed without an energy input (are spontaneous). In contrast, reactions with a positive ∆G need an input of energy in order to take place (are non-spontaneous). As you can see from the equation above, both the enthalpy change and the entropy change contribute to the overall sign and value of ∆G. When a reaction releases heat (negative ∆H) or increases the entropy of the system, these factors make ∆G more negative. On the other hand, when a reaction absorbs heat or decreases the entropy of the system, these factors make ∆G more positive.

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