The enthalpy change of an endothermic reaction is 8 kJ , and this reaction is spontaneous at 25 oC ,, what is the expected entropy change ?
thank you a lot
dG = dH - TdS
0 = 8000 - 298(dS)
To determine the expected entropy change of a reaction, we need to use the relationship between enthalpy change (ΔH) and entropy change (ΔS), which is defined by the equation:
ΔG = ΔH - TΔS
where ΔG is the Gibbs Free Energy, T is the temperature in Kelvin, ΔH is the enthalpy change, and ΔS is the entropy change.
Since the reaction is spontaneous, we know that ΔG must be negative. In order to find ΔS, we will rearrange the equation:
ΔG = ΔH - TΔS
ΔG + TΔS = ΔH
ΔS = (ΔH - ΔG) / T
Here, we know that ΔH is 8 kJ and the reaction is spontaneous, so ΔG must be negative. The value of T is given as 25°C, so we need to convert it to Kelvin:
T (Kelvin) = T (°C) + 273.15
T (Kelvin) = 25 + 273.15
T (Kelvin) = 298.15 K
The expression for ΔS becomes:
ΔS = (8 kJ - ΔG) / 298.15 K
Since we don't have the specific value of ΔG, we can't determine the exact ΔS. However, we know that ΔG is negative because the reaction is spontaneous. So, we can say that the expected ΔS will be positive or zero (but not negative).
Therefore, without the exact value of ΔG, we can't determine the precise entropy change but we can conclude that it will be positive or zero.