The G value for formation of gaseous water at 298 K and 1 atm is -278 kJ/mol. What is the nature of the spontaneity of formation of gaseous water at these conditions?
dG is negative. The reaction is spontaneous.
dG = -; rxn spontaneous
dG = 0; rxn about 50/50
dG = +; rxn not spontaneous in the direction shown but is spontaneous for the reverse rxn.
To determine the nature of the spontaneity of the formation of gaseous water at 298 K and 1 atm, we need to consider the sign of the Gibbs free energy change (ΔG).
The Gibbs free energy change is given by the equation:
ΔG = ΔH - TΔS
where ΔH is the enthalpy change, ΔS is the entropy change, and T is the temperature in Kelvin.
In this case, the given G value of -278 kJ/mol represents the enthalpy change (ΔH) for the formation of gaseous water. The enthalpy change is negative, indicating that the reaction is exothermic.
Since the given information does not provide the entropy change (ΔS), we cannot determine the spontaneity solely based on the enthalpy change. However, we can make an assumption based on the conditions given.
At 298 K and 1 atm, water is in its gas phase. The entropy change for the formation of gaseous water is generally expected to be positive, as gases have higher entropy than liquids or solids. So, if we assume that the entropy change (ΔS) is positive, we can evaluate the nature of spontaneity.
If both ΔH and ΔS are positive, then the reaction is spontaneous at high temperatures.
If both ΔH and ΔS are negative, then the reaction is non-spontaneous at all temperatures.
If ΔH is negative and ΔS is positive, then the reaction is spontaneous at all temperatures.
If ΔH is positive and ΔS is negative, then the reaction is non-spontaneous at all temperatures.
Based on what we know, the given G value is negative (indicating a negative ΔH), and we assume a positive entropy change (ΔS). Therefore, we can conclude that the formation of gaseous water at 298 K and 1 atm is spontaneously favored.
To determine the nature of the spontaneity of formation of gaseous water at these conditions, we need to look at the sign of the Gibbs free energy change (ΔG).
The Gibbs free energy change (ΔG) is related to spontaneity by the equation: ΔG = ΔH - TΔS, where ΔH is the enthalpy change, ΔS is the entropy change, and T is the temperature.
In this case, we are given the value of ΔG, which is -278 kJ/mol. Since the value of ΔG is negative, it means that the reaction is spontaneous.
When ΔG is negative, it indicates that the reaction is thermodynamically favored and will proceed spontaneously in the forward direction, without the need for external intervention.
Therefore, the nature of the spontaneity of the formation of gaseous water at 298 K and 1 atm is spontaneous.