Predict the signs of delta H (Enthalpy) and delta S (Entropy) for the evaporation of water at 85 C.
Entropy will be greater than 0 right, since there is more disorder in the gaseous state? What about the Enthalpy?
I think delta S will be + and delta H will be +. Energy must be added to the water to make it evaporate.
To predict the signs of delta H (enthalpy) and delta S (entropy) for the evaporation of water at 85°C, we need to consider two possibilities: if the process is endothermic or exothermic.
1. If the process is endothermic:
- Delta H (enthalpy) will be positive because heat is being absorbed from the surroundings to break the hydrogen bonds between water molecules during evaporation.
- Delta S (entropy) will also be positive because the randomness/disorder of the system increases as water molecules transition from the liquid phase to the gas phase.
2. If the process is exothermic:
- Delta H (enthalpy) will be negative because heat is being released to the surroundings during the formation of hydrogen bonds in the liquid phase of water.
- Delta S (entropy) will still be positive because the randomness/disorder of the system increases as water molecules transition from the liquid phase to the gas phase.
However, in most cases, the process of water evaporation is endothermic.
To predict the signs of ΔH (enthalpy) and ΔS (entropy) for the evaporation of water at 85°C, we can refer to the general principles related to the phase change of a substance.
First, let's determine the change in enthalpy (ΔH). During evaporation, water molecules gain energy from the surroundings to overcome intermolecular forces and transition from the liquid state to the vapor state.
Since heat is absorbed from the surroundings during evaporation, this means that the process is endothermic. Therefore, the sign of ΔH for the evaporation of water at 85°C would be positive (+).
Now let's consider the change in entropy (ΔS). Entropy refers to the measure of disorder or randomness in a system. When water evaporates, the molecules transition from a more ordered liquid phase to a more disordered vapor phase.
The transition from a more ordered to a more disordered state generally leads to an increase in entropy. Therefore, the sign of ΔS for the evaporation of water at 85°C would be positive (+).
In summary:
ΔH (enthalpy) is positive (+) because the process is endothermic.
ΔS (entropy) is positive (+) because the process leads to an increase in disorder.
It's important to note that the signs of ΔH and ΔS can vary depending on the specific conditions and substances involved. However, in the case of the evaporation of water at 85°C, the described tendencies are generally observed.