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

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0answers
9 views

Quantification of spontaneity of reaction

How can spontaneity of a reaction be quantified?if quantified,quantify the spontaneity of the sugar in water and salt in water.
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0answers
9 views

What is the difference between convection and conduction?

I was having a conversation with my dad the other day and he described something as happening due to convection, and it dawned on me that I have no real clue what the difference between and convection ...
0
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1answer
40 views

How to calculate the Gibbs energy for the vaporisation of solid ammonia?

Given that $P_{\ce{NH3}}=\mathrm{10~atm}$ at $298\ \mathrm K$, calculate the $\Delta G^\circ$ of the reaction $$\ce{NH3(s) <=> NH3(g)}$$ I'll begin solving the problem... I'm using the formula ...
5
votes
1answer
98 views

Reactivity of propellanes

Why is [1.1.1]propellane considerably less reactive than either [2.2.1]propellane or [2.1.1]propellane as illustrated in the hydrogenation reactions pictured below?
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1answer
42 views

Paper Towel Soaked with Isopropanol/Water Mixture Burns without Damaging the Paper. Why?

Video: https://www.youtube.com/watch?v=_qFN1hDZwp8 If you choose not to view the video, in the first demonstration a paper towel is soaked in isopropanol. As expected, the paper towel burns. However, ...
2
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2answers
50 views

Spontaneity of reversible reactions

If a reaction has positive $\Delta G$ then reverse reaction has negative $\Delta G$. How can both occur simultaneously, e.g., in a reversible reaction such as dimerisation of $\ce{NO2}$ to form ...
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2answers
48 views

How much does a light heat the air around it?

My dad told me to turn off the lights when I'm not using them because it will keep the house cooler. I don't think he is correct that a light can heat up the room. How much of a difference in the ...
2
votes
4answers
133 views

Work Done Upon Molecules

In which of the following processes is energy transferred into the substance by work ($w > 0$)? a) Expansion of a gas against the surroundings b) Expansion of a gas into a vacuum c) Vaporization ...
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0answers
26 views

Glycine nucleation simulations

I am trying to run nucleation simulations of glycine in water. To generate a supersaturated solution, a solution that will crystallize, I need to know the solubility. Luckily for me, this data exists. ...
9
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2answers
133 views
+50

Relative strength of desiccants

Is it meaningful to characterize the relative strength of desiccants? For example, is there a measure of hygroscopy, or an ordering of desiccants, such that higher ones will always dry lower ones? ...
-2
votes
1answer
37 views

Equilibrium of liquid-vapour at boiling point; which is equal, kinetic or potential energy?

A liquid is in equilibrium with its vapor at boiling point. On average do the molecules in the two phases have equal potential energy or equal kinetic energy? Why? I can't really decide ...
3
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1answer
42 views

Justification for Freezing Point Depression & Boiling Point Elevation in Solutions?

I was wondering if the following justification for freezing point depression and boiling point elevation are conceptually correct. The reason why I ask this question is because I have been self ...
2
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2answers
112 views

Physical Interpretation of Gibbs Free Energy

I know that $\Delta G = \Delta H - T\Delta S$ and that if $\Delta G$ less than $0$ a reaction will be spontaneous. What I am wondering is what is the actually physical interpretation of Gibbs free ...
2
votes
1answer
29 views

What is Enthalpy?

At school, they teach the following two formulas: $$\Delta H = -mc\Delta T$$ and $$q= mc\Delta T$$ What i am not sure is that my teacher says that q and $\Delta H$ are the same thing but to think of q ...
2
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0answers
36 views

Is white phosphorus really a cool burning fuel?

About 11 months ago, I posted a question on this SE site on cool flames. One of the answers mentioned white phosphorus. However, a few weeks earlier, I played a game called Spec Ops: The Lines, in ...
1
vote
1answer
34 views

What are analytical expressions for the isothermal change of Gibbs energy?

The change of Gibbs energy at constant temperature and species numbers, $\Delta G$, is given by an integral $\int_{p_1}^{p_2}V\,{\mathrm d}p$. For the ideal gas law, $p\,V=n\,RT$, this comes down to ...
2
votes
1answer
55 views

Understanding Gibbs free energy

I want to verify a thought I had about Gibbs free energy. In some ways, I'm actually wondering why we are using enthalpy instead of the internal energy $U$. Right now, I'm thinking that enthalpy is ...
0
votes
1answer
30 views

Rate of exothermic/endothermic reactions

Is it necessary that all endothermic reactions be slow and all exothermic reactions fast? This is based on the fact that endothermic reactions require more activation energy than exothermic reactions ...
4
votes
1answer
31 views

Derivative of Gibbs Energy wrt Temperature at constant Internal Energy

I came across with the following solution from Sandler's book: $$\begin{eqnarray}\left( \frac{\partial G}{\partial T} \right)_U &=& \frac{\partial (G,U)}{\partial (T,U)} \\ &=& ...
3
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1answer
50 views

Gibbs energy and chemical equilibrium : false proof of spontaneous generation, but why?

Let’s assume we have a reaction medium containing only simple molecules such as $\ce{H2O}$, $\ce{CH4}$, $\ce{NH4+}$ (and maybe some more). Now we consider the following equation ; $\Delta ...
2
votes
1answer
49 views

How to calculate the amount of water produced by the incomplete combustion of propane?

I was wondering if someone could walk me through how to do the following two questions? The complete combustion of pentane has a enthalpy change of $-3509~\mathrm{mol^{-1}}$. Write an equation ...
2
votes
1answer
32 views

Freeze distillation: Does efficiency depend on solubility?

I was surprised to learn that freeze distillation has the same inefficiencies as vapor distillation: Namely, that it is impossible to get two miscible fluids to fully separate in one "pass" of ...
3
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1answer
28 views

Plasma creation and condensation

Every chemical has a decomposition temperature. My understanding is that above that temperature molecular bonds are broken. And if we raise the heat high enough then all molecular bonds will break ...
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2answers
42 views

Calculating Gibbs Free Energy

This is a question from Atkin's Physical Chemistry Book. Question Suppose that 3mmol $\mathrm{N_2\,(g)}$ occupies $\mathrm{36~cm^3}$ at $\mathrm{300~K}$ and expands to $\mathrm{60~cm^3}$. Calculate ...
4
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2answers
69 views

Calculating Entropy

This is a question that appeared in Atkin's Physical Chemistry Book in the Chapter 3 exercise questions. It is question 3.3(a): Question Calculate $\Delta S$ when the state of $\mathrm{3~mol}$ of ...
4
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2answers
45 views

Why does equilibrium exist?

I've read an article that equilibrium exists when $G$ (Gibb's free energy) becomes minimum. If formation of products decreases Gibb's free energy, why won't the reaction proceed to completion so that ...
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1answer
48 views

Is the absolute temperature concept 100% viable?

Maybe I'm wrong about it but I wanted to know whether the concept of absolute temperature is real or not. As every element behaves differently at a particular temperatures how could we assign a ...
4
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1answer
61 views

Best Guide to Chemical Thermodynamics

I understand thermodynamics in a physicsy way - at the level of Callen's Thermodynamics. However, my chemical thermodynamics is quite rusty: concepts like fugacity and activity coefficients are only ...
3
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0answers
27 views

Is there a relationship between viscosity and enthalpy of vaporization?

It would be useful to be able to predict relative evaporation rates of liquids. For small reduced temperatures the heat of vaporization is relatively constant, but it is not one of the more common ...
2
votes
0answers
20 views

Generating Precipitation Diagrams with CompuTherm Pandat

I am trying to develop precipitation diagrams for an Ag-Cu-Sn alloy to figure out the kinetics involved using the CompuTherm Pandat Software (Demo Version). The precipitation diagrams need the ...
0
votes
1answer
23 views

percent ionization explanation [duplicate]

Using a weak acid as an example: $$\ce{HOAc <=> AcO- + H+}$$ The position of this equilibrium shifts to the right with increasing dilution. I have found textbooks that say this, but do not ...
7
votes
1answer
77 views

Ag-Sn-Cu Phase diagram to formulate homogenization temperature / duration

I am working on Ag-Sn-Cu alloy phase diagram to figure out the best temperature / duration to homogenize the alloy (annealing). The %age of elements in the alloy are Ag - 40 % Cu - 27.8% Sn - 32.2 % ...
5
votes
0answers
33 views

Seeking titanium compound, melting point <1600 °C, decomposes to TiO

The title says it all. I’m new to glass making, and I need a titanium compound that will render me $\ce{TiO}$ through decomposition, and has a melting point under 1600 °C. Hopefully I can get one ...
2
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1answer
79 views

Why does attraction always cause release of energy making the system more stable?

Suppose $\ce{Na^+}$ and $\ce{Cl^-}$ form an ionic bond. In doing so they will come closer by attraction. Now as they come closer their speed will increase and hence the kinetic energy increases. So ...
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0answers
23 views

Freezing point of multiple solute solution

I have 4 solutes, iron, sulfate, sulfuric acid, and peroxide. This is diluted in water and I have the molalities in mol/kg ($0.5, 0.1, 0.4, 0.35$). I tried using $\Delta T_f=−K_f\times m$, where m is ...
2
votes
1answer
48 views

Calculating enthalpy per gram mole of oxygen bond in haemoglobin

A solution of $5\ \mathrm{g}$ of haemoglobin in $100\ \mathrm{cm^3}$ of solution shows a temperature raise of $0.031\ \mathrm{^\circ C}$ for complete oxygenation. Each mole of haemoglobin binds $4\ ...
1
vote
2answers
57 views

What happens when heating water in a pressure vessel?

Suppose that I take a pressure vessel that can withstand up to 2000 PSI. Now I fill it with water (not completely, but around 90%) and start to heat it with a direct flame. What I want to know is, ...
4
votes
2answers
47 views

How is change in entropy of universe related to the energy released by system that can be used to do work?

What does change in entropy ($\Delta S$) represent ? How does change in entropy of a universe ($\Delta S_{univ}$) give us information about energy available to do work. I would like to know the ...
2
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0answers
24 views

Is there no irreversible way of moving between two equilibrium states at constant T and P?

There's a reaction occurring at constant $T$ and $P$, and it is in chemical equilibrium. Now by adding infinitesimal quantities of reactants, it is taken to another equilibrium state in a reversible ...
1
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0answers
21 views

Thermodynamic-Fuel and efficiency

Why is the maximum theoretical efficiency of Ar engine higher than that of Nitrogen engine? On a molecular level. For an Otto Cycle $\mathrm{Eff} \le\left(1-r^{1-\gamma}\right)$ ...
1
vote
1answer
37 views

Molar enthalpy vs Enthalpy of formation?

(Note I've refocused a previous unanswered question into a more general question. You can find the original much more specific question here) There seems to be two main ways of looking at the enthalpy ...
3
votes
3answers
107 views

Trying to Understand Entropy

I'm currently looking at Principles of Chemistry by Atkins, and I have a few questions involving entropy. These questions probably arise from my poor understanding of reversible/irreversible ...
3
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1answer
55 views

Heat capacity of mixtures

After reading this recent question I was interested in how to calculate the specific heat capacity of a mixture based on the specific heat capacities of its components. According to this website the ...
0
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0answers
21 views

Using equilibrium constant in gibbs equation [duplicate]

In my chemistry textbook, it is written that : Gibbs energy for a reaction in which all reactants and products are in standard state, $\Delta_\mathrm{r}G^\circ$ is related to the equilibrium ...
6
votes
1answer
117 views

What is the proper term for lines of constant volume and constant enthalpy on a thermodynamic diagram?

I know an isotherm is a line of constant temperature. Isobar is a constant pressure line. Isentrope is a line of constant entropy. But what do you call a line of constant volume? An Isochore? And ...
3
votes
1answer
58 views

Maximum Useful Work from a Process

Negative of the $\Delta G$ for a process is the maximum useful work that can be obtained from it (at constant pressure and temperature). I understood this in this way: $\Delta H$ is the heat absorbed ...
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1answer
43 views

How to Get Ideal Gas Constant R for Two Gases Mixed

One cubic container contains a mixture of gases composed of 0.02 kgmol of oxygen and 0.04 kgmol of helium at a pressure of 220 kPa. What is the temperature of this ideal gas mixture in Kelvin. ...
3
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1answer
34 views

Is it possible to calculate specific heat capacity of a compound based on its elements' heat capacities?

What the question says. For example, if I knew the specific heat capacities of lithium and oxygen, could I work out the specific heat capacity of lithium oxide with no further information?
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0answers
45 views

calculate diffusion coefficient from MSD vs time [closed]

I have a trajectory file from simulation of 20,000 frames with 5 ps time in between every frame, what I want to do is to calculate diffusion in 2 dimension (x and y axis). but to calculate diffusion ...
1
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1answer
30 views

Is enthalpy of a reaction meaningful at variable pressure?

Why should the enthalpy of a reaction be defined at constant pressure. Why can't it be defined at variable pressure?