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.

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5
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3answers
134 views

Is it possible to increase the internal energy of an ideal gas in an isothermal process?

Ideal gas is the one in which there are no attractive or repulsive forces acting and hence its internal energy is due to kinetic energy of its molecules. We may then say, for an ideal gas internal ...
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0answers
15 views

Thermochemistry calculating enthapy of formation of particular product [closed]

[![Question I found somewhere ][1]][1] [1]: https://i.stack.imgur.com/fEDY4.jpg What I have done is finding out the formation enthapy of H2o(l) which is around -286KJ/mol . Then i though of using this ...
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4answers
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Beer freezing after being opened

I am watching the Stoke vs Swansea game, & to be honest, it's pretty boring. So much so, that I've started to wonder why it is that my beer has turned into a slushy after being taken out of the ...
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0answers
29 views

How does neutralizing the charge of a coordination compound enhance its entropy?

While studying the thermodynamic stability of coordination compounds, I came across the following statement: Charge neutralization of the metal ion causes the entropy to increase which helps to make ...
2
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1answer
18k views

How to find partial pressures from a given equilibrium constant Kp?

I answered wrong on my quiz the following question on finding an equilibrium constant: For the following reaction, at $1~\mathrm{bar}$ and $300~\mathrm{K}$, partial pressures of $\ce{NO2}$ and $\ce{...
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2answers
963 views

How does an oscillating reaction work?

I watched a video showing an orange solution that goes to clear and then back to orange (and so forth.) The reaction goes through a number of cycles before it will no longer oscillate. This tells me ...
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0answers
28 views

Metalic taste of water boiled in electric kettle [closed]

Why does the water, boiled in electric kettle, taste metalic ? Do metalic ions go from metalic plate to the water through electricity ?
15
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7answers
16k views

If the human body consists of 60% water why can't we put out fire with our body? [closed]

I have often heard of people being burned at the stake, but if the body is 60% water shouldn't the fire just be put out?
7
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3answers
176 views

Why is standard state useful?

In order to calculate the equilibrium constant we must know the value of $\Delta_\mathrm{r}G^{\circ}$ (which is a function of $T$) so we can calculate $K$ as: $$K = \exp\left(-\frac{\Delta_\mathrm{r}G^...
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1answer
61 views

Do superoxide salts of heavier alkali metals contradict the principle that lattice energy depends inversely on cation-anion distance?

I have a very basic understanding of quantitative lattice energy calculations: I only know that the lattice energy is directly proportional to the product of charges on the ions and inversely ...
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2answers
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Entropy of surroundings and heat

Apparently the entropy change of a system can be found by $$\mathrm dS=\frac{\mathrm\delta q_\mathrm{rev}}T$$ I am slightly confused about this because I have seen this being used when the temperature ...
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2answers
363 views

How to calculate the standard Gibbs free energy of formation of bromine vapor at room temperature?

The normal boiling point of liquid bromine is $\pu{58.2 ^\circ C}$. At $\pu{9.3 ^\circ C}$ the equilibrium vapor pressure of liquid bromine is $\pu{100 torr}$. From this data, calculate the standard ...
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0answers
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Do antibodies move towards the antigen? [closed]

PLEASE READ: Lets say I have an antibody on a chemical linker. The linker is attached to a substrate. If an antigen comes in close proximity with the antibody, is it possible for the antibody to break ...
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0answers
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Entropy change during electrolysis of water

Consider the electrolysis of water reaction: $$\ce{H_2O -> H_2 + 1/2O_2}$$ At room temperature and atmospheric pressure, the change in enthalpy of this reaction is $\Delta H = \pu{+286 kJ mol-1}$. ...
3
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1answer
86 views

Does Raoult's law hold for immiscible liquids?

I know that Raoult's law holds true only for a non volatile solute in a volatile solvent mixture wherein the vapour pressure of the solution gets lowered due to the addition of solute. Now, first of ...
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0answers
22 views

Hydrogen permeation from low to high absolute pressure area due to difference in partial pressure?

I need to get help with a question regarding hydrogen permeation which I do not really how to get around. The statement is as following: A steel container contains helium gas at high pressure (100 ...
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51 views

Is standard change in activation Gibbs free energy indepedent of pressure?

For a chemical reaction the activation volume is defined as: $$Δ^{\ddagger}V={V^\ddagger}-V$$ where both $V^\ddagger$ and $V$ refer to standard states (I have omitted the symbol for simplicity). One ...
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0answers
23 views

Do the differential expressions of second law of thermodynamics imply a smooth increase in entropy? [closed]

Another statement of second law of thermodynamics can be formulated in terms of system properties and not properties + surroundings (isolated system). For a closed system at constant temperature and ...
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1answer
66 views

Effect of addition of inert gas on concentration in an equilibrium [duplicate]

We have the following equilibrium established in a container with movable piston at atmospheric pressure. $$\ce{N_2 (g) + 3 H2 (g) ⇌ 2NH_3 (g)}$$ Now how does the concentration of the reacting species ...
4
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2answers
128 views

Will addition of inert gas change the vapour pressure of a liquid?

From this question on Physics SE Thermodynamics of evaporation: Now imagine the experiment is repeated but instead of vacuum conditions, the water is pressurized with nitrogen at 1 atm. According to ...
2
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0answers
89 views

Error in the IUPAC Gold Book definitions of exergonic, endergonic, exothermic and endothermic?

All definitions in the IUPAC Gold Book refer to standard values: exergonic reaction (exoergic reaction) [link] This expression is often applied to a reaction for which the overall standard Gibbs ...
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2answers
644 views

The spontaneity of a redox reaction

Suppose we have a redox reaction and we want to see in what direction the reaction is spontaneous. We do this by comparing the standard reduction potentials of the sub-reactions available in the main ...
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0answers
77 views

How change in potential energy corresponds to change in enthalpy?

So while reading about activation energy , I came across this graph : Here, change in potential energy of reactant and product is depicted as ${ΔH}$, but at constant pressure and temperature , ...
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1answer
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Why is bread warm at room temperature?

If I buy a loaf of freshly-made bread and leave it out at room temperature for a day or two, when I reach into the bag the air inside is much warmer than the rest of the room. Why?
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1answer
68 views

Is ΔG the maximum non expansion work for reversible processes only?

The derivation of $$\mathrm{d}G=\delta w_{non.exp. max.}$$ $$G=H-TS$$ $$ \mathrm{d}G=\mathrm{d}H-T\mathrm{d}S-S\mathrm{d}T$$ $$\mathrm{d}G=\mathrm{d}U+P\mathrm{d}V+V\mathrm{d}P-T\mathrm{d} S-S\mathrm{...
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1answer
259 views

What's the minimum amount of energy needed to remove CO2 from the atmosphere?

I've been learning about CDR (Carbon Dioxide Removal) techniques to combat climate change. These all seem to involve extracting $\ce{CO2}$ from the atmosphere and converting to a mineral, which is ...
2
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2answers
67 views

Internal Energy Changes in Adiabatic Reactor

If we consider adiabatic reactor (one which doesn't exchange energy and matter with surroundings) with some reaction in liquid phase, energy balance for such reactor is written as heat of reaction ...
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2answers
70 views

Examples of endothermic reactions occuring spontaneously at constant temperature and pressure [closed]

Typical spontaneous endothermic processes I can think of (e.g. melting of ice, isothermal gas expansion) involve either an initial temperature difference between the system and the surroundings, or ...
0
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1answer
83 views

Why Does Electrical Work Cause Changes in Internal Energy of the System? [closed]

If we look at system at constant temperature and volume which is galvanic cell, first law of thermodynamics states: $$ dU = dQ + dW'$$ Where W' is electrical work exchanged with surroundings and Q is ...
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4answers
107 views

Reversibiliy and equilibrium

My textbook states "A system is in thermodynamic equilibrium if it is in Thermal, Mechanical, and chemical equilibrium simultaneously". The Wikipedia article on "reversible processes&...
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1answer
2k views

How to calculate the Gibbs free energy from the equilibrium constant for the decomposition of sodium bicarbonate?

Solid $\ce{NaHCO3}$ is heated to $90~^\circ\mathrm{C}$. At equilibrium the total pressure of the gases produced is $0.545~\mathrm{atm}$. Calculate $\Delta G^\circ$ at $90~^\circ\mathrm{C}$ for the ...
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0answers
54 views

Thermodynamics Property Tables

Two rigid tanks are connected by a valve. Tank A contains $0.2\ \mathrm{m^3}$ of water at $400\ \mathrm{kPa}$ and $80\ \%$ quality. Tank B contains $0.5\ \mathrm{m^3}$ of water at $200\ \mathrm{kPa}$ ...
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0answers
61 views

Regarding Ellingham diagrams

In my textbook, the following information is given about Ellingham diagram: The interpretation of $\ce{\Delta_rG^\circ}$ is based on ${K}$ ($\ce{\Delta G^\circ = -RTlnK}$). Thus it is presumed that ...
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0answers
21 views

Heat of combustion at constnat pressure and volume

Given below is a question, after reading which i had a general doubt, this is not a homework question,Heat of combustion of ethanol at constant pressure and at temperature T K is found to be −q. Hence,...
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1answer
68 views

Why is the formation free energy of carbon dioxide almost constant in Ellingham diagrams?

While reading about Ellingham diagram in my textbook, I noticed that for: $\ce{C_(_s_) + O2_(_g_) -> CO2_(_g_)}$, the standard Gibbs free energy ($\ce{\Delta_fG^\circ}$) doesn't seem to vary with ...
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0answers
33 views

What Does Electrical Work Represent in Context of Electrochemical Cells?

If cell operates reversibly than change in Gibbs energy of system equals electrical work of the cell. As far as I know electrical work is work done by electric field when charge moves between certain ...
2
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1answer
57 views

Finding equilibrium constant for the reaction between non-stoichiometric mix of gaseous components

$$\ce{CH3OH(g) + NOCl(g) <=> CH3ONO(g) + HCl(g)}$$ The volume of the container is $\pu{433 cm^3},$ $T = \pu{50 °C}.$ Methanol was added until the pressure was $\pu{50.1 mbar},$ then $\pu{0.059 g}...
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2answers
2k views

Why does changing the temperature shift the equilibrium?

I know that raising the temperature in a reversible chemical reaction causes the equilibrium to shift to the endothermic side. I know that $\Delta G = \Delta H − T\Delta S$, but I don't know how to ...
0
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1answer
54 views

Different statements of second law of thermodynamics

This may sound trivial but I am having a hard time linking different statements of second law. What I get from second law is that heat cannot be completely converted into work and hence efficiency of ...
2
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1answer
52 views

Calculate Kc with dissociation degree

If I have the reaction $$\ce{2HI (g) ⇌ H2(g) + I2(g)}$$ and know that at $T = \pu{448 °C}$ the dissociation degree $α = 0.2198,$ how do I calculate $K_c?$ I thought that it would be something like ...
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1answer
40 views

Enthalpy of Reaction and Efficiency of Electrochemical Energy Devices

For electrochemical energy devices such as batteries or fuel cells working reversibly, efficiency is defined as: $$ \eta = \frac {\Delta_rG^⦵} {\Delta_rH^⦵} $$ Since cell operates reversibly Gibbs ...
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1answer
33 views

Does the critical temperature of a gas depend on the amount of the gas taken?

Does the critical temperature of a gas depend on the amount of the gas taken? Or is it independent of it? My book does not specify this point. I think according to the gas laws, the critical ...
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1answer
595 views

Confusion on when to use mass of entire solution when performing q=mc∆T

I hope you are having a good day. I am studying for the AP Chemistry exam in May 2020. While studying, I encountered a doubt. In Problem 1 (the question on the top), the educator saw that the ...
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0answers
22 views

Is there a public database for enthalpy of solution values?

I'm looking for a public database for enthalpy of solution values. The CRC handbook only has selected compounds available. The NIST webbook doesn't appear to have any enthalpy of solution values. Any ...
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0answers
54 views

Maximum non-PV work and reversibility at constant temperature and pressure

When we talk about systems at constant temperature and pressure, maximum amount of non-PV work can be extracted if process is carried reversibly and in that case it is equal to change in Gibbs energy ...
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1answer
524 views

Work done when P,V, and T are changing simultaneously

I am given the following P-V graph for an ideal gas: I have been asked to find the work done in the process from C to A, for which $P$ is directly proportional to $V$. This may be calculated in two ...
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1answer
3k views

When the heat is absorbed by the ice then ice will melt to form liquid water

My new try: Given data Energy given by reaction =1690 kJ Initial temperature = 0 oC Final temperature = 50 oC C water = 4.18 Jmol-1 K-1 ?Hfus ice = 6.01 kJ*mol-1 Calculate Mass of ice = ? Ice ...
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2answers
957 views

Thermodynamic quantities for the freezing of water

I am trying to do the following problem: Freezing of water at $273~\mathrm K$ and $1~\mathrm{atm}$ Which of the following is true for the above thermodynamics process? p) $q=0$ q) $w=0$ r) $\Delta S_\...
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1answer
11k views

Calculating enthalpy of dissolution

In a polystyrene cup calorimeter, $4.3\ \mathrm g$ of ammonium nitrate, $\ce{NH4NO}$, was added to $60.0\ \mathrm g$ of water and stirred to dissolve the solid completely. The initial temperature ...

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