Change in Enthalpy vs Q: State Functions Explained

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In summary, change in enthalpy (ΔH) and Q are two measures of the heat energy exchanged during a process, with ΔH being a state function and Q being dependent on the process path. State functions are properties of a system that only depend on its current state, such as enthalpy and internal energy. Enthalpy and Q are considered state functions because they only depend on the current state of the system. ΔH and Q are related by the equation ΔH = Q + PΔV, where PΔV represents the work done by the system. State functions cannot be measured directly, but changes in state functions can be calculated through experiments.
  • #1
suli
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as Q(heat transfer)=P*dV + dE
Q is a non state function,
while the change of enthalpy,
dH=P*dv+dE,
i suppose it is equal to the Q above but why dH is a state function while Q is not since they are the same?
 
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  • #2
The enthalpy, H, is a state function. Is that necessarily true of change of enthalpy?
 
  • #3
so u mean dH is not a state function?
 

1. What is the difference between change in enthalpy and Q?

Change in enthalpy (ΔH) is a state function that represents the difference in enthalpy between the final and initial states of a system. It is a measure of the heat energy exchanged during a process at constant pressure. On the other hand, Q is the amount of heat energy transferred between a system and its surroundings during a process. While ΔH is a property of the system, Q is dependent on the path of the process.

2. Can you explain what state functions are?

State functions are properties of a system that only depend on the current state of the system and not on the path it took to reach that state. This means that the value of a state function will be the same regardless of the process used to achieve that state. Examples of state functions include enthalpy, internal energy, and entropy.

3. Why are enthalpy and Q considered state functions?

Enthalpy and Q are considered state functions because they only depend on the current state of the system and not on the path of the process. This is because they are both properties that are related to the energy of the system, which is a state function. Additionally, enthalpy is defined as the sum of the internal energy and the product of pressure and volume, both of which are state functions.

4. How are change in enthalpy and Q related?

Change in enthalpy and Q are related by the equation ΔH = Q + PΔV, where PΔV represents the work done by the system. This equation shows that ΔH and Q are both measures of the energy exchanged during a process, with ΔH also taking into account any work done by the system. Additionally, both ΔH and Q are reported in units of energy, such as joules or calories.

5. Can state functions be measured directly?

No, state functions cannot be measured directly. This is because they are properties that represent the difference between two states and not a physical quantity that can be directly measured. However, changes in state functions can be measured through experiments and used to calculate the values of the state functions for a given system.

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