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

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2answers
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What is the cause for thermodynamic reversible and irreversible process?

My book defines Thermodynamic irreversible process is defined as the process in which the changes take place rapidly, instead of occurring in successive stages with infinitesimal changes in ...
2
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1answer
50 views

Why is ΔE described as Q-W and Q+W in different contexts?

Depending on the textbooks looked at, the energy change is described as either Q+W or the signage is changed to Q-W. Which is correct? Is it solely context dependent? Could anyone explain the ...
3
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1answer
37 views

Can a solid and liquid be miscible?

To be specific, what I mean is: is the following situation possible? At given temperature T, there are two substances, X and Y, such that pure X is a solid, pure Y is a liquid, and X and Y mix to form ...
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0answers
11 views

How to calculate the heat absorbed by a reversible process?

Given a nonideal substance inside a box with diathermal walls, the pressure is increased reversibly. How do you calculate the heat absorbed? I assume we use dE = dq + dw = dq - pdV => dq = dE + ...
4
votes
1answer
76 views

Problems with thermodynamic derivatives

How is the following true? $$\left ( \frac{∂S}{∂P} \right )_{T}=\frac{-C_{P}}{T}\left ( \frac{∂T}{∂P} \right )_{S}$$ I know that $$C_{P}=T\left ( \frac{∂S}{∂T} \right )_{P}$$ which means the ...
2
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0answers
33 views

Is superglue a good thermal insulator?

How good of a thermal insulator is superglue compared to other materials like ceramics, plastics, and metals? I know this might not seem like a chemistry question, but I was hoping someone here could ...
1
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2answers
22 views

What is the correct definition of the Gibbs free energy of activation?

Is the following correct? Gibbs free energy of activation is used in energy profiles where the stabilities of the species are expressed as changes in Gibbs energy, while the activation energy Ea ...
2
votes
1answer
62 views

Why is the equilibrium constant given in litre per mole?

At $800\:\mathrm{K}$ a reaction mixture contained $0.5\:\mathrm{mol}$ of $\ce{SO2}$, $0.12\:\mathrm{mol}$ of $\ce{O2}$ and $5\:\mathrm{mol}$ of $\ce{SO3}$ at equilibrium. $K_c$ for the equilibrium ...
7
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1answer
88 views

Why is there sulfur in black powder / gun powder?

Black powder is composed of charcoal, sulfur and a nitrate salt. The charcoal and sulfur serve as fuel and the nitrate is the oxidizing agent. However, wouldn't it be cheaper to leave out the ...
0
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0answers
39 views

Name the equation $\Delta G=\Delta G^{\circ}+RT \ln Q$

As the title states, what is the name of the equation $$\Delta G=\Delta G^{\circ}+RT \ln Q$$ My textbook does not explicitly state the name and I could not find anything on google.
2
votes
3answers
67 views

How do breaking chemical bonds turn into kinetic energy

I’m trying to understand how breaking chemical bonds turn into kinetic energy. If AB is a chemical which breaks into A and B which zip away from each other, is it because when the bond breaks they ...
2
votes
1answer
44 views

What can we say about the Gibbs free energy if it decreases or not?

[Sorry if the question looks trivial but I have thought about it for days and red a number of books all with no success.] In almost every thermodynamics book that has something to say about chemical ...
0
votes
1answer
11 views

Calorimetry | Heat produced VS Change of enthalpy

There are two questions on the same test paper. Calculate the amount of heat energy, $q$, produced in the reaction Find the change of heat ($-q$). I'm not sure whether or not they mean the same ...
2
votes
1answer
31 views

Synthetical formation of diamonds

As everyone knows a diamond won't last forever. It will eventually turn into a graphite over a long period of time, as the free energy of graphite is lower than that of diamond, hence making the ...
1
vote
2answers
19 views

How can I find the heat that will be released in kJ per gram for the reaction of Al with Fe2O3?

Find the heat that will be released in kJ per gram when aluminium ($\ce{Al}$) reacts with $\ce{Fe2O3}$ as follows : $\ce{2Al(s) + Fe2O3(s) → Al2O3(s) + 2Fe(l)}$ the information given is: $\Delta H ...
1
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0answers
23 views

∆Enthalpy of diatomic molecules

Question: The reaction between hydrogen and oxygen to yield water vapor has $\Delta{}H^\circ = -484~\mathrm{kJ}$. How much $PV$ work is done, and what is the value of $\Delta{}E$ in kilojoules ...
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3answers
100 views

What is the name of the formula ΔE = q + w?

What is the name of this formula? Google could not provide me with an answer. $$\Delta E=q+w$$
1
vote
1answer
23 views

In what ways does the transfer of heat affect bond stability?

It is to my understanding that certain amount of joules may change an element's/compound's physical state given a certain temperature. How does a certain added number of joules affect the orbital of a ...
1
vote
0answers
9 views

Relating Thermodynamic & Transport Properties to Electrochemical discharge curve

What are the fundamental thermodynamic & transport properties that the discharge cycle of a rechargeable battery with an intercalating cathode (like Li-ion) should depend upon? The few that I ...
2
votes
1answer
29 views

Is the activity coefficient always a constant?

The activity of a species $i$ is defined as $a_i = e^\frac{\mu_i-\mu_i^\ominus}{RT}$, with $\mu_i$ the chemical potential, and $\mu_i^\ominus$ the chemical potential under standard conditions. Very ...
0
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1answer
32 views

How do you calculate enthalpy for a reaction at non-standard conditions?

I understand how to calculate the change in enthalpy and entropy for a reaction in standard conditions, but is there a way to calculate these values at non-standard conditions? Also, is there any way ...
2
votes
2answers
110 views

Steric Hindrance and Bronsted Basicity

Does steric hindrance affect Bronsted basicity? I understand that basicity is a thermodynamic quality. Not a kinetic factor. So it doesn't matter if it takes a million years for the proton to reach ...
0
votes
1answer
56 views

calculate the amount of energy in KJ necessary to convert 346 g of liquid water from 0 C to water vapor at 182 C

Calculate the amount of energy in $\mathrm{KJ}$ necessary to convert $346~\mathrm{g}$ of liquid water from $0~^\circ\mathrm{C}$ to water vapor at $182~^\circ\mathrm{C}$. The correct answer is ...
1
vote
1answer
566 views

Does ice melt faster when submerged in water?

Suppose you have a container with a drain at the bottom full of frozen H2O which you leave a room temperature to melt. Will the ice melt faster if you drain the water as it melts? I would expect that ...
0
votes
1answer
37 views

Equilibrium Graphs

What if I2 and H2 began at the same concentration - then do we start at the same point? ... or is it acceptable to start at different concentrations...
0
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1answer
20 views

Equilibrium Practical Discussion Help

I understand the theory, but am struggling to answer the following discussion questions: (i) Why isn't this represented by: Fe3+ (aq) + 3 SCN- (aq) <-> Fe(SCN)3 (aq) Why do we dilute the ...
3
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1answer
63 views

On 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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1answer
128 views

Kinetic and Thermodynamic Stability

My prof noted that if the two components of any ionic compound undergo a large extent reaction with each other, then the substance CANNOT exist as a pure substance. For example, consider ammonium ...
7
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1answer
56 views

Does having constant pressure imply a temperature change? Why isn't the volume needed to calculate the final temperature and energy?

Calculate the final temperature and the change in internal energy when $500\:\mathrm{J}$ of energy is transferred as heat to $0.900\:\mathrm{mol}$ $\ce{O2(g)}$ at $298\:\mathrm{K}$ and ...
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2answers
31 views

Can compressed CO2 sprayed onto a hot mass/liquid be an effective means to cool it?

I thought the answer was obvious, but endless google searching has revealed nothing but speculation and people who have completely conflicting opinions. Some people say CO2 absorbs no heat, others say ...
1
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1answer
51 views

Greater entropy: an atom or macromolecule?

A question that appeared on my last chemistry exam was : Which of the following has greater entropy A) An atom B) A macromolecule The question doesn't specify anything else(i.e. type/size ...
4
votes
1answer
55 views

Determine the ΔH for the reaction in kJ/mol of ethanol?

A $1.000~\mathrm{g}$ sample of ethanol, $\ce{C2H5OH}$, was burned in a bomb calorimeter whose heat capacity had been determined to be $2.71~\mathrm{kJ/C}$. The temperature of $3.000~\mathrm{kg}$ of ...
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1answer
82 views

Why do ionic substances with higher lattice energies tend to be less soluble in water than substances with lower lattice energies

I understand that that energy is required to overcome intermolecular forces holding solute particles together in the crystal but I don't understand how this relates to lattice energies and its ...
1
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0answers
35 views

Neutralisation of HCl with NaOH - generated heat and excess concentration [closed]

If you have $75\:\mathrm{mL}$ of $M(\ce{HCl}) = 4\:\mathrm{M}$ at $25\:\mathrm{^\circ C}$ and $100\:\mathrm{mL}$ of $M(\ce{NaOH})=5\:\mathrm{M}$ at $27\:\mathrm{^\circ C}$ with a final temperature ...
0
votes
2answers
27 views

Calculate the second ionization energy for the Mg from the following data?

here is a problem : What I did " as shown in the picture below " I rewrote the information given in terms of reactants and products ( equations )// in Part 1 Then I used the Hess law to obtain ...
0
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1answer
27 views

What is the relationship between pressure and stoichiometry ratios

This is the question from the textbook. Ozone O3 can be prepared in the laboratory by passing an electrical discharge through oxygen gas. Assume that an evacuated steel vessel with a volume of 10L ...
2
votes
1answer
33 views

Thermodynamic question - Work during a reversible compression

I have a short multiple choice question that I have already solved. The question is The work done during a reversible compression (Vi (initial) = V1; Vf = 1/6V1) of an ideal gas is? I chose ...
4
votes
3answers
64 views

Why is the enthalpy of vaporization greater than the enthalpy of fusion?

Why is the molar enthalpy of vaporization of a substance larger than its molar enthalpy of fusion (at constant pressure); for example, in the case of ice and water.
1
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1answer
28 views

How does dichlordifluormethan get into the stratosphere?

I was currently wondering why FCKWs are able to destroy the ozone layer. It looks for me like these gases have a high molecular weight in comparison to $\ce{N2}$ or $\ce{O2}$. How can these gasses ...
2
votes
1answer
62 views

Justify the rearrangement of the ideal gas law

For example, lets say we have a question where we have to use the ideal gas law and lets say that moles and temperature are constant. Then the gas law can also be written as $$n\mathcal{R}T=PV.$$ ...
1
vote
1answer
41 views

What is the mass of 1 Liter of ethylene at 2000 bar pressure?

I was wondering the weight of 1 liter of ethylene at 2000 bar and 310 Kelvin? I have tried to just multiply the weight at 1 bar with 2000 but I don't think i got the correct answer because the answer ...
3
votes
4answers
83 views

What is reactivity really, and can it be quantified?

I understand the concept of a reactive species on a sort of vague and intuitive level: a reactive species is one that has lots of reactions that it can participate in. These tend to have large kinetic ...
2
votes
0answers
29 views

Supercritical Steam Expansion

Ten $\mathrm{kg}$ of steam at $500~\mathrm{bar}$ is expanded at constant pressure until its volume increases to seven times its initial value of $0.01~\mathrm{m^3}$. (a) Calculate the initial and ...
3
votes
1answer
58 views

Why does ice cream not go back to its original form upon refreezing?

I came from a birthday party and someone gave me a sundae. I'm already full so I just decided to eat it at home. After arriving at home the sundae melted. So I left it in the freezer overnight. When I ...
2
votes
1answer
46 views

…If the final temperature of the combined liquids is 28.5 C and heat capacity of the calorimeter is 19.3J/C determine the specific heat of methanol?

A question in the book says : A $25.95 g$ sample of methanol at $35.6 °C$ is added to a $38.65 g$ sample of ethanol at $24.7 °C$ in a constant pressure calorimeter If the final temperature pf the ...
1
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1answer
37 views

What total energy (in kJ) is contained in 1.0 mol of photons, all with a frequency of 2.75 • 10¹⁴ Hz?

There is a question, that says: What total energy (in $\mathrm{kJ}$) is contained in $1.0~\mathrm{mol}$ of photons, all with a frequency of $2.75 \cdot 10^{14}~\mathrm{Hz}$? My answer was: The ...
2
votes
0answers
53 views

Who is Hræðraford, the “learned clerk” “writing in modern chemical Latin”?

Truesdell, C. Rational Thermodynamics. New York, NY: Springer New York, 1984. http://dx.doi.org/10.1007/978-1-4612-5206-1, p. 41 says: … in the numerous papers and books whose titles and topics ...
2
votes
1answer
57 views

Can I use the hypotenuse of the pythagorean theorem to compute the work?

A friend of mine told me that she used the hypotenuse of the pythagorean theorem to compute the work in graph below and the to compute the coefficient of efficiecy in this thermodynamics triangle ...
2
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1answer
61 views

Units for dissociation constant and relationship to Gibbs Free Energy

How does one "convert" between an equilibrium constant calculated from the Gibbs free energy for a dissociation reaction and experimentally determined dissociation constants? $$ \Delta ...
3
votes
0answers
65 views

How can we justify setting the affinity $\sum_i \mu_i \nu_i$ equal to zero at chemical equilibrium?

Let $\sum_A \nu_A A \rightarrow \sum_B \nu_B B$ be a general reaction whose progress during time interval $dt$ is measured by $d\zeta$, so the amount of reactants consumed and products generated in ...