Question

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met? a. ΔS° > 0, ΔH° > 0 b. ΔS° > 0, ΔH° < 0 c. ΔS° < 0, ΔH° < 0 d. ΔS° < 0, ΔH° > 0 e. It is not possible for a reaction to be spontaneous at all temperatures.

Answer 1

Answer:

b. ΔS° > 0, ΔH° < 0

Explanation:

According the equation of Gibb's free energy -

∆°G = ∆°H -T∆°S

∆°G = is the change in gibb's free energy

∆°H = is the change in enthalpy

T = temperature

∆°S = is the change in entropy .

And , the sign of the  Δ°G , determines whether the reaction is Spontaneous or non - Spontaneous or at equilibrium ,

i.e. ,

if

• Δ°G < 0 , the reaction is Spontaneous

• Δ°G > 0 , the reaction is non - Spontaneous

• Δ°G = 0 , the reaction is at equilibrium

The reaction has the value for ∆°H < 0 i.e. negative, and ∆°S > 0 i.e. , positive

Now ,

∆°G = ∆°H -T∆°S

= ( - ∆°H ) - T( + ∆°S )

= ( - ∆°H ) - T( ∆°S )  

∆°G = negative

Hence ,

Δ°G < 0 , the reaction is Spontaneous  .