Questions tagged [thermodynamics]

Applicable to questions about heat, energy, work, and their interconversion in chemistry. See the tag wiki for a detailed list of topics. Questions tagged may also be tagged with [enthalpy], [energy], [free-energy] where appropriate.

Filter by
Sorted by
Tagged with
-7
votes
0answers
20 views

Pls help with w=-nRTln(vf/vi) problem DUE IN 10 MIN [on hold]

A sample of gas in a cylinder of volume 3.87 L at 257 K and 2.88 atm expands to 7.61 L by two different pathways. Path A is an isothermal, reversible expansion. Calculate the work for Path A. Answer ...
0
votes
1answer
31 views

Where am I wrong in the concentration potential calculation?

With regard to concentration cells I have seen $E^\circ_\mathrm{cell}$ being calculated to be zero. However we have had this notion that $$E^\circ_\mathrm{cell} = E^\circ_\text{cathode(reduction)} - ...
2
votes
3answers
57 views

Is enthalpy of combustion the 'heat released' or 'enthalpy change'?

In a constant volume calorimeter, $\pu{3.5 g}$ of a gas with molar weight $\pu{28 g}$ was burnt in excess $\ce{O2}$ at $\pu{298 K}.$ Temperature of calorimeter increased from $298$ to $\pu{298.45 K}$ ...
-1
votes
0answers
13 views

Calculating the enthalpy and entropy [on hold]

I would like to know the answer and comment of this question Caculate the enthalpy and entropy changes of1mol Diopside as it is heated at 1atm from 600k to 1000K. Standard state of 298.15K and 0....
0
votes
0answers
11 views

Does the enthalpy of neutralization depend upon the nature of strong acid and strong base? [on hold]

In the book it's written that if the acid is dibasic then the enthalpy of neutralization will be 27.4 kcal but then at some other place it is written that it is independent of the nature of strong ...
-4
votes
0answers
38 views

Least/Lowest London Dispersion Force! [on hold]

What/Which would be the least London Dispersion Force? In the human body. And How many eV would it be?
0
votes
1answer
24 views

Change in enthalpy equation [on hold]

If the formula for change in enthalpy is ΔH=ΔU+pΔV, and ΔU = q - pΔV then shouldn't the formula be simplified to ΔH = q regardless of whether the volume or pressure is constant? Is this only true when ...
4
votes
1answer
70 views

Is it really possible for a liquid to stay afloat a gas (vapor)?

I have a book at home called Chemical Thermodynamics for Process Simulation (I have the first edition) and at the very beginning of chapter 2 of the book one may read the following: No reference is ...
-2
votes
0answers
17 views

Thermodynamics1and thermo chemistry [closed]

At 0°C and 1 atmosphere pressure, the volume of 1mole of an ideal monoatomic gas is 22.415litres. The gas is expanded until its pressure is 0.4 atmosphere by reversible adiabatic process determine the ...
0
votes
2answers
32 views

Work done in cyclic process [on hold]

I have been told that when ∆V=0, work done will be zero (W=0). I know that, in cyclic process ∆V will be zero, since it's a path function and |W| i.e. magnitude of work done will be the area enclosed ...
-3
votes
0answers
20 views

can fire ignite Hydrogen? [closed]

Hypothetically speaking,If there is a Hydrogen leak in a room, and a fire is ignited, will it ignite the hydrogen, and if it does, how strong will the explosion be? Just curious.
0
votes
1answer
41 views

Heat exchange in adiabatic process

I know my teacher told me that In adiabatic process there is no exchange for heat between system and surrounding. Then he came to point. From first law of thermodynamics $$∆U = q + W \tag{1}$$ ...
-1
votes
1answer
21 views

Why Gibbs energy change of a process can be negative at constant temperature and pressure? [closed]

This question has been asked before, but the answers are not clear and satisfactory. If the pressure and the temperature are constant then G would be always zero. How would then G have a value other ...
0
votes
1answer
32 views

Irreversible Adiabatic Process [closed]

While studying about the entropy change of surroundings in irreversible adiabatic process, I came across a sentence. For infinite reservoir, all processes are considered reversible And suddenly ...
0
votes
1answer
41 views

What is reversible work? [closed]

I am not getting the intuition behind reversible work? What exactly is reversible work? What does it mean when someone says that in reversible work can be reversed by an infinitesimal amount at any ...
-1
votes
0answers
20 views

What does it mean when we say Gibbs free energy in standard state?

I have heard my professor mentioning that standard Gibbs free energy has to do with constant pressure and has nothing to do with constant temperature. However in Ellingham diagrams in particular I ...
0
votes
1answer
42 views

qualitatively: Why are thioesters more reactive than regular esters? [duplicate]

In ochem students are taught that shorter bonds (like alkynes) have more energy than longer bonds such as alkanes. However in biochem we are taught that thioesters are very energetic bonds and release ...
5
votes
1answer
129 views

What is the true meaning of Gibbs energy and chemical potential?

After doing some research and reading I found some problems which I will try to state as clearly as possible. The definition of Gibbs Free Energy says "the greatest amount of mechanical work which ...
4
votes
0answers
49 views

Is pH in a charged hydrogel and its supernatant solution constant?

Let us assume we deal with ideal systems without interactions. The gel phase and the supernatant solution phase are in thermodynamic equilibrium. The supernatant solution shall consist of different ...
-1
votes
0answers
17 views

what is the entalphi formation of c3h8 knowing these equations [duplicate]

i have 3 equations $C_3H_8 + 5O_2 -> 3CO_2 + 4H_2O \Delta H = -2220 kJ$ $3C + 3O_2 => 3CO_2 \Delta H = 3(394) kJ$ $4H_2 + 2O_2 => 4H_2O \Delta H = 4(286) kJ$ i have to get to $3C + 4H_2O =...
7
votes
0answers
97 views

Why are IUPAC's definitions of exo- and endothermic disconnected from the direction of heat flow?

I'm wondering if anyone can provide a rationale for IUPAC's definitions of exothermic and endothermic, since they disconnect these terms from the direction of heat flow. Specifically, here are IUPAC'...
-1
votes
1answer
34 views

Equilibrium pressure

Ammonium carbamate dissociates as follows: $$\ce{NH2COONH4(s)<=> 2NH3(g) + CO2(g)}$$ The value of $K_p$ for this reaction is found to be equal to $\pu{2.92 \times 10^-5 atm^3}$. If ...
1
vote
1answer
26 views

What are D_b and D_a in the Generalized Fugacity Coefficients table?

I've been referring the book: Chemical Process Principles: Part-II Thermodynamics. I found a table that gives me fugacity coefficients in a tabular form corresponding to various reduced pressures and ...
-1
votes
1answer
22 views

Bond energy and enthalpy of formation

Is the following equation true? $$\ce{∆_fH} = \ce{∆_{BE_{reactants}}H} - \ce{∆_{BE_{products}}H}$$ where $BE$ stands for Bond energy and $f$ stands for formation. I read that, $$\ce{∆_fH} = \ce{∆_{...
2
votes
1answer
50 views

Can someone walk me through this gas mixture question?

Argon $(\ce{Ar})$ and helium $(\ce{He})$ are initially in separate compartments of a container at $\pu{25 °C}.$ The $\ce{Ar}$ in compartment A which has a volume $V_\ce{A}$ of $\pu{9.00 L}$ and a ...
3
votes
1answer
33 views

Isothermal vs adiabatic compression of an ideal gas [closed]

Could someone please explain these specific questions physically (especially the first question!)? I understand the corresponding mathematical proofs, but not the physical reasoning? I have looked ...
0
votes
1answer
42 views

Enthalpy and heat relationship

They say that enthalpy of reaction is the heat when at constant temperature and pressure. So if enthalpy is $$\mathrm dH = \mathrm dU + p\,\mathrm dV = T\,\mathrm dS - p\,\mathrm dV + p\,\mathrm dV + ...
2
votes
3answers
87 views

Genuine confusion about the equilibrium constant [closed]

I gather that the equilibrium constant K = 1 implies that, at equilibrium, neither the forward nor the backward reactions are thermodynamically favoured. But if pressure of the system increases and ...
-1
votes
1answer
36 views

Enthalpy change of water [closed]

A given amount of (liquid) water in an open vessel is heated from 20 degree celsius to 50 degree celsius. Suppose it absorbs x joule in the process. What is the enthalpy change in the process? Is it = ...
0
votes
0answers
29 views

Standard state conditions in thermodynamics

Standard state conditions for standard Gibbs energy change stipulate (among other conditions) that partial pressure of each gas = 1 bar. e.g. 2A + 3B = 4C + 5D (all gases) Then for standard Gibbs ...
2
votes
1answer
94 views

Mathematical justification for Le Chatelier's principle

At equilibrium $$ \begin{align} K &= \exp\left(\cfrac{TΔS^\circ - ΔH^\circ}{RT}\right)\\ ⇒ \frac{\mathrm d \ln K}{\mathrm dT} &= \frac{ΔH^\circ}{RT^2} \end{align} $$ If enthalpy change is ...
-1
votes
0answers
13 views

Can reactions take place above decomposition temperature of one of the products?

Can reactions take place above decomposition temperature of one of the products? For example: K2O -> K2O2 + K (above 350°C) K2O2 -> K2O + K (above 500°C) Would the first reaction still take place ...
-1
votes
0answers
29 views

Numerical analysis of Hydrogen bond between F- and CH3COOH

The hydrogen bond between $\mathrm{F^{-}}$ and $\mathrm{CH_{3}COOH}$ is very strong and is strength may be analysed by setting up a Born Haber cycle, with the following data (in $kJ/mol$): Lattice ...
1
vote
1answer
57 views

How to find the Cp, difference of Cp and heat of fusion from the dependence of vapor pressure on temperature?

The vapor pressure of zinc varies with temperature as $$\log P(\pu{mm Hg}) = -6850/T - 0.755\log T + 11.24 \label{eqn:1}\tag{1}$$ and that of liquid zinc as $$\log P(\pu{mm Hg}) = -6620/...
1
vote
0answers
58 views

How to I find the equilibrium temperature in this problem?

From Castellan's Physical Chemistry, chapter 12 [1, p. 276]: 12.18 At $\pu{25 °C}$ we have for rhombic sulfur: $ΔG_\mathrm{f}^\circ = 0,$ $ΔS^\circ = \pu{31.88 ± 0.17 J K-1 mol-1};$ and for ...
1
vote
1answer
57 views

Constant Pressure and Temperature during Phase Change

One of the solution guides to a question I was working on said that pressure and temperature is constant for a phase change. I understand why temperature is always constant for a phase change, but don'...
2
votes
1answer
64 views

Application of Nernst Equation in Potentiometric titration of Fe2+ with Ce4+

It is well Known that to find $E_{cell}$ during titration of $Fe^{2+}$ with $Ce^{4+}$ we consider 3 domains: Before Equivalance point , $E_+ = E_{Fe^{3+}/Fe^{2+}}^o+\frac{RT}{nF}log\frac{[Fe^{3+}]}{...
0
votes
0answers
29 views

Software to predict equilibrium products in the ideal gas phase

I'm interested in software packages that can answer the following kind of question: If I mix 30mol% $N_2$ and 70mol% $H_2$ together at 2 bar and 2000C, what is the equilibrium composition after all ...
-1
votes
0answers
48 views

Chemical Equilibrium problem

I can't seem to get the answer that appears on the back of the book Here is what i did: a) $K_p=K_x p^{\Delta N}$; in this reaction $\Delta N =-1$, then $K_pp=K_x$ from $\Delta G=-RT\log K_p$ I ...
-1
votes
1answer
59 views

Boiling point elevation does not depend on the solute? [closed]

I've recently carried out an experiment trying to measure the boiling point elevation of water after adding 5M of NaCl and KCl. Although for some reason, KCl solution started boiling around 90 degree ...
2
votes
2answers
83 views

Temperature measurement

Consider some liquid in a beaker. I am measuring its temperature using a thermometer. When i put my thermometer's bulb in the liquid, the particles of the bulb gain the same kinetic energy as of the ...
1
vote
2answers
30 views

Spontaneity of an exothermic chemical reaction

When the process is exothermic (ΔHsystem​<0), and the entropy of the system increases (ΔSsystem​>0), the sign of ΔGsystem​ is negative at all temperatures. Thus, the process is always spontaneous. ...
1
vote
4answers
74 views

Basic concept of the first rule of thermodynamics

There is a cylinder-piston system with some gas in it, and let's say this system is a closed system. Say that the system is submerged in a large beaker of water whose temperature is $25\ \mathrm{^\...
-1
votes
1answer
27 views

What is the the total heat extracted in the process? [closed]

Since this is a cyclic process:- Change in internal energy=0. In the process C-A the work done W is zero, thus the heat Q is zero since it is an isochoric process. Next in the process A-B, I got the ...
0
votes
2answers
48 views

Temperature measurement using thermometer [closed]

I have two samples of water – 'A' and 'B'. My thermometer measured them to be 90 °C. They both have different volumes. So, the kinetic energy of the particles of sample A and B is same or different? ...
1
vote
0answers
41 views

What is the degree of freedom of the calcium carbonate dissociation reaction?

Question $\ce{CaCO3}$ dissociated in a closed system according to the reaction: $$\ce{CaCO3(s) -> CaO(s) + CO2(g)}$$ Assuming the reaction is in thermodynamic equilibrium, what is/are ...
1
vote
0answers
36 views

Identifying endothermic and exothermic reaction [closed]

How can I know that a given reaction is endothermic or exothermic? I know that all combustion reactions are exothermic. But what about other reactions? In my school exam I was asked about whether the ...
0
votes
3answers
2k views

Are all volatile liquids combustible?

I realized that liquids like petrol, kerosene and even perfumes are combustible when they are volatile. Could that be the reason why water is not combustible is because it is not volatile? Are ...
1
vote
0answers
42 views

Calculating thermodynamic quantities for hydrogenation of iron nitride

HW#6.3 If the reaction $$\ce{Fe2N(s) + 3/2 H2(g) <=> 2 Fe(s) + NH3(g)}$$ comes to an equilibrium at a total pressure of $\pu{1 bar},$ analysis of the gas shows that at $\pu{700 K}$ ...
2
votes
0answers
85 views

Why can't calorimetry be used to measure fast reactions?

As my previous post was a bit unclear and unspecific, I am reformulating it. First of all this is a question that I had while reading some concepts my book introduces, so this isn't a homework ...