A reaction is always non-spontaneous when
a. ∆H>0, ∆S>0
b. ∆H>0, ∆S<0
c. ∆H<0, ∆S<0
d. ∆H<0, ∆S>0
Gibb's Free Energy is
a. the difference between the activation energy and reaction enthalpy
b. the difference between the enthalpy of the reactants and products
c. the sum of the enthalpy and entropy
d. the usable energy leftover in a reaction
always non-spontaneous when dS<0 and dH>0. Looks like b.Do you understand why?
dG = dH - TdS.
For spontaneity dG must be -. So when
dH is >0 it is +; when dS <0 is is - and -TdS is +. + added to + is + and when dG is + the reaction doesn't go anywhere by itself.
Next question. dG = dH - TdS
d is the answer. G is the amount of usable work.
For the first question:
A reaction is always non-spontaneous when the conditions are such that the ∆H value is positive (greater than 0) and the ∆S value is negative (less than 0).
So, the correct answer would be option b. ∆H>0, ∆S<0.
For the second question:
Gibb's Free Energy (∆G) is a measure of the energy available to do work in a chemical reaction. It is related to both the enthalpy (∆H) and entropy (∆S) of the system.
Therefore, the correct answer would be option c. The sum of the enthalpy and entropy.
To determine whether a reaction is spontaneous or non-spontaneous, we can use Gibbs Free Energy (ΔG). The formula for ΔG is ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, ΔS is the change in entropy, and T is the temperature in Kelvin.
For the first question, we need to consider the signs of ΔH and ΔS.
Option a: ΔH > 0, ΔS > 0
In this case, since both ΔH and ΔS are positive, the sign of the first term (-TΔS) in the ΔG equation will depend on the temperature. If TΔS is larger than ΔH, then ΔG will be negative and the reaction will be spontaneous. If ΔH is significantly greater than TΔS, then ΔG will be positive and the reaction will be non-spontaneous.
Option b: ΔH > 0, ΔS < 0
In this case, since ΔH is positive and ΔS is negative, the first term (-TΔS) in the ΔG equation will also be negative. Therefore, ΔG will be positive regardless of the temperature, and the reaction will be non-spontaneous.
Option c: ΔH < 0, ΔS < 0
In this case, both ΔH and ΔS are negative. Since both terms in the ΔG equation will have the same sign (positive or negative), the sign of ΔG will depend on the temperature. If TΔS is larger in magnitude than ΔH, then ΔG will be negative and the reaction will be spontaneous. If ΔH is significantly greater than TΔS, then ΔG will be positive and the reaction will be non-spontaneous.
Option d: ΔH < 0, ΔS > 0
In this case, ΔH is negative and ΔS is positive. The first term (-TΔS) in the ΔG equation will be negative, and the sign of ΔG will depend on the magnitude of ΔH compared to TΔS. If ΔH is larger in magnitude than TΔS, then ΔG will be negative and the reaction will be spontaneous. If TΔS is significantly greater than ΔH, then ΔG will be positive and the reaction will be non-spontaneous.
Therefore, the correct answer is option b. When ΔH > 0 and ΔS < 0, the reaction is always non-spontaneous.
For the second question, Gibbs Free Energy (ΔG) is the usable energy leftover in a reaction. None of the provided options accurately define Gibbs Free Energy. Therefore, the correct answer is none of the above.