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Questions tagged [physical-chemistry]

The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.

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Interpretation of Raoult law

In attachment I have tried to derive Raoult's law by using the concept of equilibrium constant. There is nothing mentioned in my text book about how this equation comes about, so I decided to do it ...
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0answers
12 views

Chemistry Question [on hold]

What volume (in milliliters) of 0.230 M NaOH should be added to a 0.135 L solution of 0.0150 M glycine hydrochloride (pKa1 = 2.350, pKa2 = 9.778) to adjust the pH to 2.99?
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0answers
21 views

What actually happens when 'energy is released'?

Thermodynamics classes and equations always discuss a chemical reaction in the form of energy being released or absorbed. This is always hand-waved as just 'energy' from the surroundings. What's ...
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28 views

Exact definition of n-factor [duplicate]

I have been studying about the n-factor of different kinds of compounds(acids, bases, salt, etc) in many different reactions. However, even after much research on the internet, I can't find the exact ...
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0answers
24 views

Two different answers obtained by balancing this chemical equation!! Somehow [duplicate]

This is the concerned equation: $\ce{ XeF4 + H2O -> Xe + XeO3 + HF + O2}$ This can be balanced as $\ce{6 XeF4 + 12 H2O -> 4 Xe + 2 XeO3 + 24HF + 3 O2}$ or $\ce{5 XeF4 + 10H2O ->3 Xe + ...
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1answer
18 views

Understanding “Gay-Lussac's law of Gaseous volumes/combining volumes”

Understanding "Gay-Lussac's law of Gaseous volumes/combining volumes". So I was reading Wikipedia and stumble across this. It defines it as follows "The ratio between the volumes of the reactant gases ...
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1answer
33 views

Henry law and equilibrium

Is Henry's law a consequence of equilibrium between the gas in aqueous phase and gas in gaseous phase? What I mean is, is it correct to treat Henry law as a manipulation of equation for equilibrium ...
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0answers
36 views

Le Chatelier's Principle Having No Effect

Consider the following equilibrium system: $$\ce{2 IBr(g) <=> I2(g) + Br2(g)}$$ Would a decrease in the volume of the system effect the equilibrium? I think it would not affect the ...
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21 views

Evaporation of alcohol from a 40% alcohol wash [on hold]

I have a 250ml 40% alcohol (80% proof) liquid. How long will it take for all the alcohol to evaporate at 100 degrees Celsius?
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1answer
52 views

Thermodynamics: ΔU = Q + W or U = Q?

Heat is the total kinetic energy of all atoms of the system. When work is done on the system it means that a part of system kinetic energy is used to do the work, and this work makes the surrounding ...
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35 views

Question of raoult's law [on hold]

Liquid A and B form an ideal solution after mixing. 4 moles of A and 6 moles of B are taken in a cylinder. A piston is fitted to it and a pressure of 0.9 ATM is maintained. Q1) Predict whether the ...
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0answers
12 views

finding x in FeSO4 xH2O [on hold]

FeSO4 xH2O contains 37.2% of water complete the calculation to determine x 1-Mass of one mole of H2O= 18g 2-Mass of water in 100g of FeSO4 xH2O= 37.2g 3-Number of moles of H2O in 100g of FeSO4 xH2O=...
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1answer
20 views

Find ratio of quantities of water and of argon in airtight container

I am working on my EJU exam past papers (2013) and got stuck at this question. Knowledge of high school or first year university chemistry is assumed. I honestly do not know where I should start. ...
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2answers
49 views

Implication of negative order on kinetics

In the reaction $$\ce{2 O3 -> 3 O2}$$ the order of reaction that I have been taught is $$\ce{O_3 \underset{$k_{-1}$}{\overset{$k_{1}$}{<=>}} O_2 + O}$$ $$\ce{O_3 + O \overset{$k_{2}$}{->...
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12 views

Aluminum, Stainless Steel, in Water [on hold]

Can I neutralize a reaction that is occurring between Aluminum particulate, Stainless Steel particulate in water
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3answers
120 views

Calculating ΔG at the extremes of reaction extent

This question follows on from a great post on comparing $\Delta_\mathrm{r} G^{\circ}$ to $\Delta_\mathrm{r} G$ answered here The G vs ξ graph that is used in the answer is an excellent tool to ...
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0answers
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85.2 grams of sodium sulfate and 66.7 grams of lead (II) chloride react. Write the balanced equation. Identify the limiting and excess reactant [on hold]

85.2 grams of sodium sulfate and 66.7 grams of lead (II) chloride react. Write the balanced equation Name each of the products Classify the reaction Identify the precipitate Identify the limiting and ...
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0answers
25 views

How equivalent mass or equivalent can be related to this? [closed]

Of two oxides of iron, the first contained 22% and the second contained 30% of oxygen by weight. The ratio of weights of iron in the two oxides that combine with the same weight of oxygen is. I found ...
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0answers
13 views

Stoichiometry calculations in chemistry moles to mass and volumes step by step calculations [closed]

Calculate amount of reactants required for formation of 9×10^23 molecules of Water from hydrogen and oxygen.
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0answers
13 views

Potassium alum powder, hydrogen peroxide, water and baking powder [closed]

I added these three in a bottle (out of nowhere) and it started bubbling. And when it subdued, the liquid was kinda hotter than normal (hydrogen perox) and my finger is kinda rough. So i want to know ...
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1answer
32 views

Help reading a phase diagram? [closed]

How does the y axis work? If the pressure I am looking for is 10^‐4 to 10^‐3 nbar? I tried doing log of the yaxis but its giving me numbers that are not even close to what I am looking for.
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1answer
38 views

Changes in entropy and Gibbs free energy for sublimation at triple point [closed]

The standard enthalpy of sublimation of dry ice (solid carbon dioxide) is $\Delta H=6.03\ \mathrm{kJ/mol}$. The triple point of $\ce{CO2}$ is at $p=5.1\ \mathrm{atm}$, $T=-56.7\ \mathrm{^\circ C}$. I ...
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1answer
31 views

Why is the entropy of solidifying solution higher than that of a pure solvent?

According to a source, Solutions have a greater entropy than pure liquids as the particles in a solution are more separated and solvent molecules separate the solute particles. If the number of ...
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1answer
39 views

Surface chemistry [on hold]

Why doesn't the process of chemisorption form multimolecular layers whereas he physisorption with lesser force of attraction between molecules form multimolecular layer?
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1answer
33 views

How can I find the emf of a cell given the individual reduction and oxidation reactions and their respective potentials? [duplicate]

If I am given the individual oxidation and reduction half-equations, how can I find the emf of the combination? For example: $$ \begin{align} E^\circ(\ce{Fe^3+}/\ce{Fe^2+}) &= \pu{0.77 V}\\ E^\...
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0answers
25 views

How to compare the |∆H| and |∆U| from each of the following reactions? [closed]

Can I do : |∆H| = |∆U| + ∆nrT ? Or do I need to evaluate the stability of the compounds from the reactions and then compare ∆U and ∆H ?
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0answers
21 views

Why does internal rotation of ethane give an energy spectrum asymptotically approaching a rotation based on $\nu=1$ rather than $\nu=0$?

I'm a physicist with very little knowledge of chemistry. Recently a chem colleague left a molecular model in my classroom, so I brought it back to her, and as I was walking down the hall with it, a ...
2
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0answers
31 views

Gibbs free energy of activation and activation energy

What the difference between Gibbs free energy of activation and activation energy
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0answers
65 views

Aren't all of our chemical equilibrium calculations wrong? [duplicate]

Let us consider a chemical equation $$\ce{aA + bB → cC + dD}$$ $$r_\mathrm{fwd} = k_\mathrm{fwd}[\ce{A}]^α[\ce{B}]^β$$ where $a ≠ α$ and $b ≠ β$, as it is not necessary that order is equal to the ...
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0answers
13 views

maximum work by electrochemical cell [closed]

Calculate maximum work done and equilibrium constant for the following reaction at 298 K: 2Cr(s) + 3Fe2+(aq) ----------> 2Cr3+ (aq) + 3Fe(s). Given E0Cell = 0.30V.
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1answer
31 views

In a galvanic cell, why do electrons move through the wire from zinc to copper?

I understand that there is aqueous $\ce{Cu^2+}$ in this scenario which pulls on the electrons from the zinc causing the electrons to move through the wire, but how does the electronegativity of $\ce{...
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0answers
43 views

Calculate correct heat output of chemical reaction

A solution with 1 mole $\ce{NaOH}$ is mixed with a solution of 1 mole $\ce{HCl}$ and the total volume is 1 L. The initial temperature is 25 °C. My question is regarding calculating the correct heat ...
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0answers
47 views

Gibbs energy at a certain temperature

For the reaction $$\ce{1/2 N2(g) + 3/2 H2(g) -> NH3(g)}$$ $ΔG$ at $\pu{298.15 K}$ is $\pu{-3980 cal},$ and the change in enthalpy is given by the expression: $$ΔH = -9.19 - 7.12T + 3....
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1answer
76 views

Is a hydrogen molecule smaller than hydrogen atom?

Recently I came across a textbook of physical chemistry which stated the following: In the formation of a stable hydrogen molecule, two hydrogen atoms share a pair of electrons between them and two ...
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1answer
30 views

What are the primary, secondary and tertiary physicochemical properties of ionic liquids?

In the following sentence ..the ability to modulate the individual components presents an advantageous framework for tuning secondary and tertiary physicochemical characteristics without ...
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3answers
43 views

Reason Behind Decrease In Potential Energy [closed]

Atoms combine to gain stability. They gain stability when they lose energy. In my book, it's given that the potential energy of the system is reduced during chemical combination. But I am eager to ...
5
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2answers
62 views

Is temperature double-counted in the Gibbs free energy equation?

Complete amateur here. When looking at one form of the equation deriving the change in Gibbs free energy for a given chemical reaction, the terms change in enthalpy, and the negative product of ...
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0answers
26 views

What will be the form of coulomb and exchange operators for electron m in an n-electron molecule?

I know that the Fock operator for electron $m$ in $n$-electron molecule would be: $$\hat{f}\!(m)u_i(m) = \varepsilon_iu_i(m)$$ $$\hat{f}\!(m) \equiv -\frac 1 2 ∇_m^2 - \sum_α\frac{Z_α}{r_{ma}} + \...
3
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1answer
167 views

Can anyone help me with this question on vibrational modes of free base porphyrin (C20H14N4)?

4 a. The structure of free-base porphyrin $(\ce{H2P}$, chemical formula: $\ce{C20H14N4})$ is shown below. Given that this molecule belongs to the $D_\mathrm{2h}$ point group (character table given ...
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2answers
23 views

Given solubility of sodium carbonate, find mass of hydrate sodium carbonate dissolved?

I am working on a problem from my scholarship exam practice (MEXT). I am not quite sure if I got it right. The question was provided with multiple choices (a) to (f) below: The solubility of sodium ...
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0answers
30 views

Reaction Mechanism with a Rate Determining Step

Just a quick question on how to deal with multiple intermediaries in a proposed reaction mechanism. Here is the overall reaction: $$\ce{I-(aq) + OCl-(aq) -> IO-(aq) + Cl-(aq)}$$ Here is the ...
4
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2answers
140 views

Solubility in different pressure conditions

I am working on my scholarship exam practice. I believe this exam assumes high school + first year university knowledge. And I'm not quite sure what I did wrong. Could you please have a look? The ...
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0answers
11 views

What is the difference between radii of Gyration and hydrodynamic radii of a polymer? [closed]

Why do you consider that the relationship between RH and RG should depend on the quality of the solvent?
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0answers
29 views

First order reaction

I am little bit confuse about relating the half life time period of a first order reaction something like $$\ce{2A -> B + C}$$ Here the rate of reaction will be half of the rate at which $\ce{A}$ ...
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0answers
32 views

What kind of chemical reaction happens when combining Tahini and Date syrup?

While both Tahini and Date syrup are quite thin, when mixed together they form a paste-like substance that is very delicious, and quite thick. But what kind of chemical reaction leads to such sudden ...
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0answers
33 views

Steric factor is greater than one will the collision frequency determined by the arrhenius equation be greater or less than the experimental value? [closed]

In a bimolecular reaction the steric factor p was experimentally determined to be 4.5 Experimentally determined value of frequency factor is higher than that predicted by Arrhenius equation ...
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1answer
36 views

In a weak acid-strong base titration why is [H+] no longer equal to [A-] after addition of the base? (A2 level chemistry)

I understand that before any base is added $\ce{[H+]}$ is equal to $\ce{[A-]}$ but why is $\ce{[H+]}$ no longer equal to $\ce{[A-]}$ when the strong base is added? If all the following reactions ...
1
vote
1answer
60 views

Why do we use external pressure when calculating work done by gas? [duplicate]

For irreversible expansion and compression, why is dw= -pextdV but not dw= -pdV ? Many of the texts and related questions on this site I encountered give a same general idea: because work done= ...
2
votes
2answers
176 views

How do you calculate the correct charge on F after F2 dissociates?

When you ionize $\ce{F2}$ to $\ce{F2^5+}$, it quickly dissociates. Experiments show that the products of dissociation are $\ce{F^2+}$ and $\ce{F^3+}$. I have tried to model the dissociation of $\ce{...
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1answer
63 views

Calculating the ph of an unknown solution by measuring the precipitate [closed]

You have an unknown metal hydroxide, but no meters or indicators. You have lead (II) nitrate, which is soluble in it, and lead (II) hydroxide that is insoluble in it. You take one liter of the unknown ...