# Tag Info

### Why does Entropy Increase on mixing two ideal liquids

If we have $1$ mol each of two different types of ideal gasses (He or Ne for example) at the same pressure and in two equal volumes separated by a partition if you remove the partition the gasses will ...
• 30.7k
Accepted

### Why does Entropy Increase on mixing two ideal liquids

Entropy is a measure of the number of ways (configurations) in which a system (the liquids before or after mixing) can be arranged subject to constraints such as the pressure and temperature. At the ...
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### Mathematical proof that more work is done in an isothermal than an adiabatic expansion?

As Poutnik states in the comments, since the integrand is the same, if we can prove that $p_\mathrm{isothermal}(V) > p_\mathrm{adiabatic}(V) \; \forall V$, that would be enough. Since pressure is ...
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### Mathematical proof that more work is done in an isothermal than an adiabatic expansion?

Let: $W_\mathrm{T}=\mathrm{isothermal\;work}$ $W_\mathrm{A}=\mathrm{adiabatic\;work}$ $y=\frac{W_\mathrm{T}}{W_\mathrm{A}}$ $x=\frac{V_\mathrm{o}}{V}$ $\lambda=\gamma-1$ Dividing both work expressions:...
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1 vote

### Isobaric expansion vs Isobaric Free Expansion

If the volume of gas increases, but pressure stays the same, then something must be steadily supplying heat. PV = nRT yields T = PV/nR If P stays the same, and V increases, so must T. This is ...
• 33.4k
Accepted

### Finding the point where reaction switches from endothermic to exothermic

Basically the slope of the adiabatic curve would satisfy the slope of the PV diagram, at a point where the curve and the PV line intersect (The PV line becomes tangent to the adiabatic curve). Based ...
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### Finding the point where reaction switches from endothermic to exothermic

From the first law of thermodynamics, $$dU=dQ-dW$$ The process goes form endothermic to exothermic when dQ=0. This is also tangent to some adiabatic reversible curve for the gas.
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### Standard Enthalpy of Formation of Refrence state(A consequence or assumption) and H+(aq)

It would be bad if you set the enthalpy of formation for both diamond and graphite to zero because one can react to form the other (and the enthalpy of reaction is non-zero). However, it is fine to ...
• 40.7k
Accepted

### Closest attempt to making a Carnot Engine

The real life inefficiency of the Carnot cycle has nothing to do with nonideality of the system elements or their frictional losses or other dissipative issues. The real life efficiency problem with ...
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### Equation of state for gas and liquid

I think i found the reason. Peng-Robinson is very steep and inaccurate at the gas-liquid boundary and even the smallest change in volume leads to enormous changes in pressure. The error could be as ...
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### Author claims that for an ideal gas dU/dV=0

The internal energy depends on the random kinetic energy and the potential energy of interaction of the molecules. The latter is equal to zero when the specific volume is very high and the molecules ...
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### Author claims that for an ideal gas dU/dV=0

The main idea is to obtain a mathematical expression only involving the measurable variables $p$, $T$, and $V$. We start with the internal energy as a function of its canonical variables. ...
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1 vote

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### Gibbs energy of an imperfect crystal

I think you have a good understanding of the matter because what you say is correct. You might find the paper by Mosquera-Lois et al. [1] interesting where they go deeper in this balancing between ...

### Why do we have water vapor at room temperature and atmospheric pressure when water is a compressed liquid at these conditions?

Why do we have water vapor at room temperature and atmospheric pressure when water is a compressed liquid at these conditions? If we kept vapor partial pressure below saturated vapor pressure, we ...
• 42.3k
Accepted

### Why do we have water vapor at room temperature and atmospheric pressure when water is a compressed liquid at these conditions?

I think that it is a good question: if you have ice in liquid water, even at 1°C (just above the melting point), all the ice will disappear and you will have 100% liquid. Then why do you have always ...
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1 vote

### Why do we have water vapor at room temperature and atmospheric pressure when water is a compressed liquid at these conditions?

Think of molecules of water liquid escaping into vapor, and molecules of water vapor condensing into liquid. Both processes occur simultaneously, and an equilibrium is reached in a closed system. The ...
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### Two different approaches for calculating enthalpy change for methane + HCl

The first formula is only used to calculate the difference in energies of the reactants and products, so for this you have your endothermic and exothermic graphs to determine $\Delta{H}$. The second ...
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1 vote

### Will the total equilibrium pressure increase in gas phase reaction PCl5(g) ⇌ PCl3(g) + Cl2(g) after chlorine is removed?

After giving this problem more thought, I have come up with a better demonstration for why equilibrium pressure will decrease after removing the chlorine gas. Let: A = $\ce{PCl5}$ C = $\ce{PCl3}$ D = \$...
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### Chemical reaction that can produce lots of heat from 2-3 simple liquid ingredients?

You do not state the end purpose of this quest. If you simply want to turn heat into electricity at a controlled temperature the source of heat is not relevant. If the purpose is to find a chemical ...
• 2,179
1 vote

### The correct way of formulating change in enthalpy

Algebraically,$$P_2V_2-P_1V_1=\left(\frac{P_2+P_1}{2}\right)(V_2-V_1)+\left(\frac{V_2+V_1}{2}\right)(P_2-P_1)$$So, in your equation, you should be using the arithmetic average pressure and arithmetic ...
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Note that $$\text{d}(pV)=p.\text{d}V + V.\text{d}p, \tag{1}$$ but \begin{align} \Delta(pV) &= p_2V_2 - p_1V_1 \\ &\ne p \cdot \Delta V + V \cdot \Delta p\tag{2} \end{align} \begin{align} \...