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Which of the following is true for the reaction NH3(l) NH3(g) at –33°C and 1 atm pressure? (The normal boiling point for NH3 is –33°C.)
Answer
Question 8 answers
ΔH = 0
ΔS = 0
ΔH = PΔV
ΔH = ΔnRT
ΔH = TΔS
DeltaH=TdeltaS
The correct answer is ΔH = TΔS.
To determine which of the statements is true for the reaction NH3(l) to NH3(g) at -33°C and 1 atm pressure, we can utilize the given information and knowledge about the reaction conditions and thermodynamics.
First, let's understand the statements and their meanings:
1. ΔH = 0: ΔH represents the change in enthalpy, which is the heat transferred during the reaction. If ΔH = 0, it implies that there is no heat transfer occurring during the transformation.
2. ΔS = 0: ΔS represents the change in entropy, which is a measure of the disorder or randomness in a system. If ΔS = 0, it means that there is no change in the entropy of the system.
3. ΔH = PΔV: This statement represents the relationship between enthalpy change and pressure-volume work. It implies that the enthalpy change is equal to the product of pressure and the change in volume of the system.
4. ΔH = ΔnRT: This equation represents the relationship between enthalpy change and the number of moles involved in the reaction. It states that the enthalpy change is equal to the product of the change in the number of moles (Δn), the ideal gas constant (R), and the temperature (T).
5. ΔH = TΔS: This equation represents the relationship between enthalpy change and entropy change. It implies that the enthalpy change is equal to the product of the temperature (T) and the change in entropy (ΔS).
Now, let's analyze the given reaction:
NH3(l) -> NH3(g)
Since the reaction is going from liquid NH3 to gaseous NH3, it is a phase change process. At -33°C, which is the normal boiling point of NH3, the liquid NH3 is boiling and converting into the gas phase. This means the reaction is an endothermic process since heat is required to change the phase from liquid to gas.
Considering this, we can eliminate options 1 and 2: ΔH = 0 and ΔS = 0.
Option 3, ΔH = PΔV, is not applicable in this case because the reaction is a phase change, not a change in volume.
Option 4, ΔH = ΔnRT, is also not applicable because the number of moles of NH3 is the same in both the liquid and gas phase.
Therefore, the correct answer is option 5: ΔH = TΔS. In this case, since the reaction is an endothermic phase change, the enthalpy change (ΔH) is directly proportional to the temperature (T) and change in entropy (ΔS).
So, for the reaction NH3(l) -> NH3(g) at -33°C and 1 atm pressure, the enthalpy change (ΔH) can be expressed as ΔH = TΔS.