Questions relating to heat and its relation to other forms of energy in chemistry.

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21
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3answers
3k views

Does any known substance ignite on cooling?

As the title says, I'm interested to know if there's any substance or combination of substances which ignites (or even increases its chance of spontaneous ignition) when cooled. I've never heard of ...
2
votes
1answer
23 views

It is possible to make an homogeneous solution of water and oil?

I wondered if in certain condition like very high pressure(so that water and oil remain liquids) and very high temperature(so that the variation of the Gibbs energy is negative--> ∆G = ∆H-T*∆S) we can ...
-2
votes
1answer
22 views

Spontaneous processes:Explain the following line please [on hold]

Explain the following line, please: The natural (spontaneous) processes follow a non-equilibrium path and as such are irreversible but these processes proceed up to establishment of equilibrium.
0
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2answers
47 views

How does the London force work at absolute zero? [on hold]

Consider a molecule such as pentane which is mostly attracted to other molecules by dispersion forces. If there is no heat and no fluctuations in electron positions how would a liquid or solid hold ...
1
vote
2answers
30 views

Why is the value of “a” is positive instead of negative in Van der Waals equation?

Higher value of a means higher atttraction force between molecules. Attraction force causes the pressure to be less than expected. Now the actual pressure becomes $P + \frac{n^2a}{V^2}$ . Which means ...
0
votes
1answer
23 views

Thermodynamics in Solution (solvation) from quantum chemistry

The gist of the question is "how do I get a heat of formation in solution" - but let me give it some context to be more specific. I am interested in calculating the thermodynamic values of molecules ...
3
votes
2answers
46 views

Work is not a state function

From Work-Energy Theorem we have, Work = Change in kinetic energy = Final K.E - Initial K.E This shows that work only depends on the final and initial value of K.E independent of the path. ...
-1
votes
0answers
16 views

Thermodynamic process & cycle [closed]

an ideal gas has a volume of 0.3m3 at 350k and 4 bar was compressed in adiabatical process to 12 bar. Later on the gas was cooled in isochornic and further the gas was expanded in isothermal so as to ...
1
vote
1answer
19 views

Given a theoretical combustion engine, how can I calculate the output of this engine depending on the fuel it uses?

I'm writing a Minecraft mod (for those who don't know, it's sort of like a smaller "program" that loads into the Minecraft game and expands it, by adding other things to it). My question is: consider ...
1
vote
1answer
57 views

Isothermal process gives V = A(T)exp(-KP)?

Substance with isothermal compressibility K, where $\mathrm{K = -\frac{1}V(∂V/∂P)_T}$ undergoes constant isothermal, mechanically reversible process from state ($P_1$, $V_1$) to ($P_2$, $V_1$) where V ...
0
votes
1answer
28 views

Why don't we use enthalpy of fusion and enthalpy of vaporisation as two separate terms in Born-Haber's cycle?

I am not able to understand why we use enthalpy of sublimation rather than enthalpy of fusion and enthalpy of vapourisation of solid sodium metal in a Born-Haber cycle for the formation of NaCl from $...
1
vote
1answer
33 views

3 component (ternary) system in equilibrium

If the components of a system were Cl2, Br2, and I2, how could I describe this system under equilibrium conditions when the number of phases is at a maximum? If there are 3 components, using the ...
1
vote
2answers
46 views

Do thermodynamically favourable chemical reactions always proceed?

I wanted to know some common parameters which decide the feasibility of any chemical reaction. And can we make a non favourable reaction favourable.
3
votes
2answers
55 views

Work done on a container, resulting in pressure change

Why does pumping gas into a rigid container (causing the pressure and temperature to increase), not mean that work has been done on the container? Work is given by the formula : W = -P ΔV If I go ...
0
votes
1answer
50 views

Why does Raoult's law work? [duplicate]

I am trying to look for the entropy explanation but I do not understand anything I can find. Please keep it simple but talk about it from a entropy point of view. Use water and a volatile solute as an ...
1
vote
1answer
26 views

What guarantees that there is a thermodynamic equilibrium in a closed chemical reaction network independently of the mass-action kinetics? [closed]

I would like to know according to which we can state that there is a unique equilibrium of a closed chemical reaction network (at constant circumstances) without supposing mass-action kinetics if time ...
4
votes
3answers
67 views

Entropy change of a rubber band

When I stretch a rubber band, the fibers straighten out causing lesser randomness and more order. This should imply the entropy of the rubber band has decreased, but how does the entropy of the whole ...
0
votes
1answer
45 views

Complete transfer of Heat into Work

During an isothermal reversible expansion of a gas, all heat absorbed by the gas from the reserviour is being used up to push the piston up. But doesn't this contradict something like the second law? ...
3
votes
2answers
85 views

Why does more heat transfer take place in a reversible process than in a irreversible process?

We have defined $$\mathrm dS=\frac{\delta Q_\text{reversible}}{T}$$ and the second law of thermodynamics (Clausius inequality) says $$\mathrm dS\geq\frac{\delta Q}{T}$$ (Here $\delta Q$ is just the ...
-1
votes
0answers
49 views

Why isnt ethanol a base? [duplicate]

Why isnt ethanol a base since it contains an OH group? I realize it is an alcohol but what happens when it is suspended in water?
-1
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0answers
11 views

Acids in aqueous solution [duplicate]

Why do acids donate a proton to water? For example, HCl. I realize it ionizes to form H+ and Cl- and the hydronium ion is formed. Why scientifically does this happen? Why does the H donate its proton ...
0
votes
1answer
36 views

Effect of an inert gas on steam vapor pressure at equilibrium

Suppose we have a closed container with mobile walls, so it will change its volume in order to equal the external pressure(constant) to the internal pressure. This container has inside it a liquid ...
0
votes
1answer
39 views

Is the deprotonation of phenol exothermic?

I just wanted to confirm that deprotonation reaction of weak acids are exothermic? I know that strong acids deprotonate exothermically (e.g. adding liquid $\ce{H2SO4}$ to water releases a lot of heat),...
0
votes
3answers
50 views

Work and entropy

I am not able to conceive why work wouldn't increase the entropy of a system. If i am compressing a ideal gas adiabatically and reversibly, the gas pressure inside would increase,meaning more no of ...
7
votes
4answers
901 views

Why does entropy increase when the difference in temperatures is decreased?

In irreversible heat transfer, heat energy is irreversibly transferred from the higher temperature system to the lower temperature system, and the combined entropy of the systems increases. Source: ...
1
vote
2answers
33 views

Is there a way to counteract the problems with weighing hot objects?

I am currently performing an experiment in which it would be greatly beneficial to be able to accurately measure the mass of a hot object without waiting for it to cool. The current plan is simply to ...
1
vote
2answers
67 views

Can equilibrium be reached in a non-reversible chemical reaction?

Can chemical equilibrium only be achieved in a reversible process? I have only seen equilibrium in processes that are reversible so I was wondering if it were possible in reactions that are not ...
2
votes
3answers
150 views

Does ∆Gº exist?

To the best of my understanding, the quantity of Gibbs free energy of an entity depends on its concentration in the system. Equilibrium is reached when ∆G = 0, or when the Gibbs free energies of all ...
1
vote
0answers
40 views

Derivation of the Lever Rule

To derive the Lever rule, the textbook I am reading sets: $$nz_A = n_\alpha x_A + n_\beta y_A\\ nz_A = n_\alpha z_A + n_\beta z_A$$ $x_A =$ liquid phase mole fraction of component $A$ $y_A =$ gas ...
1
vote
1answer
60 views

Why are non-spontaneous reactions driven in the presence of energy?

Here is my understanding. If you have an endergonic reaction (m) with $\Delta G_m=-m$ and you couple it to an exergonic reaction (n) with $\Delta G_n=n$, where $n>m$, then the endergonic reaction ...
-1
votes
1answer
61 views

Immersing copper and zinc in hydrochloric acid

I am wondering what would happen if a metal strip of copper and a metal strip of zinc were immersed in solution of $\ce{HCl}$ in standard electrochemical conditions. I have calculated the standard ...
0
votes
0answers
67 views

Decomposition of CaCO3 in a sealed vessel

For the equilibrium $$\ce{CaCO3(s) <=> CaO(s) + CO2(g)}$$ $\Delta H^\ominus = 178\ \mathrm{kJ\ mol^{-1}}$ and $\Delta S^\ominus = 160\ \mathrm{J\ mol^{-1}}$. I'm asked to suppose that $1\ \...
2
votes
3answers
70 views

Is ΔS of a system related to temperature and change in enthalpy?

I often see the equation $\Delta S_\text{universe}$ = $\Delta S_\text{surroundings}$ + $\Delta S_\text{system}$, where $\Delta S_\text{surroundings}$ can be re-expressed as $\dfrac{-\Delta H_\text{...
-2
votes
1answer
49 views

What is the solution to Kauzmann's paradox?

Kauzmann's paradox is the paradox of what happens when a liquid is supercooled below the temperature at which the difference in entropy is zero.
0
votes
1answer
46 views

Triple Point Equation

Is there any equation that can calculate the triple point of a substance? Because a method for calculating the critical temperature and the Boyle temperature of a substance that I posted in another ...
1
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0answers
20 views

Why is the specific heat of ethanol not representing experiments

I am in my last year of high school completing an assignment hot and cold packs, and particular the enthalpy behind them. My major lack of understanding is why my calculations are working for heat of ...
1
vote
1answer
36 views

What really is an equation of state (EOS) and how are they developed?

Are EOSs merely correlations that mathematically represent (in a better or worse way) experimental data or do they have a theoretical background? How are they developed (suppose one wishes to develop ...
0
votes
1answer
40 views

Hess's Law/Enthalpy of reaction problem

The problem: Chloroform, $\ce{CHCl3}$, is formed from methane and chlorine in the following reaction: $$\ce{CH4(g) + 3Cl2(g) ->3HCl(g) + CHCl3(g)}$$ Calculate $\Delta rH^{\circ}$, ...
0
votes
1answer
15 views

Difference between free energy of formation and free energy of combustion [closed]

I was wondering what is the main difference among those two values.
1
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0answers
17 views

Heating of mixture of gases with one gas barely above its boiling point

What happens when mixture of two gases is heated in a closed container? If one gas expands faster than the other and increases pressure of the container enough so that the boiling point of the other ...
0
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0answers
22 views

Question on surface tension and adsorption

I just read that positive adsorption is observed with solutes which are hydrophobic when water is the solvent, and alcohol in water is given as an example (which was then generalized as polar organic ...
-2
votes
2answers
38 views

How to obtain saturated pressure of water at 200 ºC using fugacities

The target is to obtain saturated pressure of water at 200 ºC using PHI-PHI (fugacity coefficients) approach,so it means it's a VLE of water only,so we write equilibrium condition: $f_i(l)=f_i(v)$ (*)...
0
votes
1answer
36 views

Decomposing chemical compounds - Ease of Decomposition [closed]

Someone asked me a question, that which of the following can be decomposed chemically: Ammonia Iron Neon Hydrogen Flourine My Analysis: At first attempt I answered Ammonia but changed it to 'I ...
0
votes
1answer
43 views

What is the difference between the chemical potential μ and the molar Gibbs free energy Gm?

I'm not too sure if I understand this correctly: Is the $G_\mathrm{m}$, the Gibbs free energy of the entire system, divided by the amount of substance making up the system, while $\mu$ is the Gibbs ...
2
votes
1answer
70 views

How to derive Van't Hoff equation for Henry's constant

While studying about Henry's Law, I encountered this equation,I didn't know how to derive it so I searched about it and got nothing, I tried to substitute $H$ (Henry's const.) by $\gamma\cdot f_i$ ...
0
votes
1answer
48 views

Heat Transfer during Phase Change

When ice is melting, we know that the temperature stays constant at 0 ℃. If we were to place ice at 0 ℃ in a sufficient amount of water at ambient temperature, would the temperature of the water ...
0
votes
0answers
15 views

How is temperature dependency on pressure measured in an adiabatic process experimentally?

I've been studying Maxwell's equations recently. While solving some exercises, I stumbled upon the expression of the dependency of temperature regarding pressure at constant entropy: $$\frac{∂T}{∂P}∣...
0
votes
1answer
42 views

Mass of Ice during Phase Change

If 18g of ice at a temperature of -6 ℃ is placed in 250 g of water at 20 ℃, we know that there is enough energy supplied by the water to completely melt the ice and transform it into liquid. My ...
-2
votes
2answers
71 views

What is at 298 K at standard entropy?

The standard entropy of a substance is the entropy of $1$ mol at $298$K and $1$ bar pressure. What exactly is at $298$K? The system or the surrounding? Let's take vapour as an example where $ \ \ce{...
2
votes
0answers
42 views

Entropy Change of Resistor

A very large swimming pool filled with water of temperature equal to $20\mathrm{^\circ C}$ is heated by a resistor with a heating power of $500\ \mathrm{W}$ for $20$ minutes. Assuming the water in ...