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

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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 ...
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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...
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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 ...
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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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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 ...
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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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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 ...
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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 ...
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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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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 $$n\mathcal{R}T=PV.$$ ...
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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 ...
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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 ...
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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 ...
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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 ...
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…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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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On Spontaneity of the Redox Reactions

According to this Mc Graw-Hill link during a spontaneous redox reaction Gibbs Free Enthalpy must decrease and at the same time the change in the Gibbs Free Enthalpy is the maximum electric work that ...
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Help with simple DIY procedure to measure diffusion?

While I am not asking the question here, a recent question concerning osmosis at the Bio SE caught my interest. In a nutshell that question was, given isotonic solutions of sugar inside and outside an ...
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How exactly do you measure the free energy of a reaction?

It is to my understanding that ΔG can be positive or negative given whether the reactant is exothermic or endothermic. How would you go about measuring the energy (in joules) of a reaction using the ...
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How can we calculate enthalpy change in a closed tank containing methanol adsorbed by activated carbon?

Here's the problem in the simplest way: I have a closed box containing methanol adsorbed by activated carbon. The box is made from copper. A pipe is connected to that box, which has condenser on the ...
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Thermodynamics Problem

If we put a piece of coal in open air we don't get any energy of it.But if we put fire to it in open air we get energy.Explain it with help of Gibbs free energy.
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How to make approximation of rotational partition function of diatomic linear molecules?

Using the rigid rotor approximation to the level energies, and such other appropriate assumptions, we can approximate rotational partition function, $Q_{\mathrm{rot}}$, of linear molecules as follows: ...
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What is the extent of a reaction between an acid and its conjugate base?

What is the extent of say, this reaction? $\ce{H_2CO_3 + HOCO_2^- <=> HOCO_2^- + H_2CO_3}$ K for the reaction appears to equal 1, and given the stoichiometry of the reaction, this implies that ...
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In the lattice model, what's a nearest neighbor?

I was reviewing my grad Thermodynamics textbook to go over a concept that I never learned well: the Lattice model. One set of equations1 has: $zN_1=2N_{11}+N_{12}$ $zN_2=2N_{22}+N_{12}$ where $z$ ...
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Why May K Expressions Be Manipulated As Such?

Why is the above massaging of various K expressions valid? Something in me says "Hess's Law." But then doesn't that deal with enthalpy? What's the true reason?
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Activation Energy in Acid/Base reactions

For simple acid/base reactions - i.e. those involving inorganic compounds - does activation energy ever play in reactions? Or can we ignore kinetics entirely and just consider thermodynamic factors ...
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Can Entropy Increase During Bond Formation?

Recently the question was asked, "Is Bond Formation “Strictly” Exothermic?" As a corollary to that question, what is the relationship between entropy and bond formation? Does the entropy of the bond ...
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Why does calcium carbonate decompose into calcium oxide?

Why does calcium carbonate, when heated strongly, decompose into calcium oxide and carbon dioxide? What is the mechanism? Can someone illustrate the means by which this happens? What ...
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Why is N₂ stable but HCN and C₂H₂ unstable?

Compounds with triple bonds generally seem to be unstable. $\ce{HCN}$ and $\ce{C2H2}$ are high-energy, relatively short-lived molecules that will readily polymerise or react with other organic ...
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Will ice cream freeze faster with frozen brine or adding salt to ice?

I've been making some ice cream without a ice cream maker, using salt, ice, mixer and steel canister since I can't get a ice cream machine around here and its fun. It works pretty good but it seems ...
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Furan and maleic anhydride: Why is the major product exo?

For most Diels-Alder reactions, the product is endo because there are favorable interactions between the newly forming pi-bond and the electron withdrawing groups of the dienophile. Why is the ...
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Specific question about multiple choice question

I have searched for this answer on line but I cannot find an answer. I know this is a Le Chatelier's principle question. The question: $\ce{2NO(g) + H_2(g) <=> N_{2}O(g) + H_{2}O} + ...
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Suggestions for research into different fluids in heat pipes

I'm doing some research on heat pipes (check here for wiki). One of the things I'm planning to do is try some different fluids in the pipes. Water (commonly used) has a freezing point that's too high, ...
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Hess Cycle, determining enthalpy change of formation

I am asked to find the enthalpy change of formation of the following: $$\ce{N2 + 1/2O2 -> N2O}$$ I am given the following enthalpies of reaction: $$1:\:\ce{C + N2O -> CO + N2} \:\:\:\Delta H_f ...
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Refrigeration cycle

I have a question about the refrigerant's pressure in the inlet of an evaporator. Why should the sat-temp of the refrigerant be below the required temp of the cooled compartment ? Shouldn't the ...
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Thermodynamics adding salt to water changes the temperature

$5\:\mathrm{g}$ of an unknown salt are dissolved in $325\:\mathrm{g}$ of water. Both the water and the salt are initially the same temperature. The water's temperature falls by ...
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How can a phase be thermodynamically stable at room temperature if it only appears at high temperature?

How can a phase that appears at high temperature be thermodynamically stable at room temperature? For example, $\alpha$-alumina is a phase that is formed at temperatures above $1000^\circ C$. How is ...
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What is the formula for heat of vaporization under reduced pressure?

I haven't taken a chemistry class in several years, and I have honestly been searching the web for the past hour and can't find anything. I know this is something basic we learned back in high school ...
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Why is the equilibrium constant wrong for this Gibbs free energy problem?

Solid $\ce{NaHCO3}$ is heated to 90°C. At equilibrium the total pressure of the gases produced is 0.545 atm. Calculate $\ce{ΔG°}$ at 90°C for the reaction $\ce{2 NaHCO3(s) ⇌ Na2CO3(s) + H2O(g) + ...