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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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1answer
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Model of an ideal liquid in chemistry

In chemistry there are ideal models/concepts of ideal crystal, ideal gas and even ideal solution, but there is no model/concept of ideal liquid. In physics (fluid dynamics, to be precise) there is a ...
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0answers
26 views

Temperature increase in the reaction between magnesium and steam [on hold]

I want to approximate the temperature increase for a piece of magnesium reacting with steam $$\ce{Mg(s) + H2O (g) → MgO (s) + H2 (g)} \quad\Delta H = \pu{-360 kJ mol-1}$$ So, I've made a couple of ...
3
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1answer
31 views

Compound having highest standard reduction potential

Which compound has highest SRP (standard reduction potential) value, e.g. the strongest oxidising agent? In most tables $\ce{F2}$ is at top with $E^\circ = \pu{2.87 V}$, but I've found a table listing ...
4
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1answer
132 views

Soil-solution cations in competition for exchange sites

How could one determine the likelihood of one cation displacing another on a negatively charged exchange site of a clay particle? For example, in a soil solution containing equal parts (by number of ...
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0answers
21 views

Deriving the entropy as a function of concentration

In a physical chemistry class, the professor derived entropy $S$ as a function of concentration starting from $S=k\ln(W)$. Somehow he made a mistake and ended up with the wrong sign. This remains ...
27
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2answers
5k views

Can magnetic fields affect a chemical reaction?

This question was asked recently in an interview and I just said that "Yeah, like if the reaction involves ions or paramagnetic species". But the interviewer went on and asked me to elaborate on HOW ...
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0answers
11 views

Salt bridges in electrochemistry [duplicate]

What is the role of the salt bridge in a galvanic cell? The cell which I am studying is between a copper half cell and zinc half cell.
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0answers
23 views

Why does the pH of a reaction between magnesium and hydrochloric acid stay the same?

I did an experiment where I reacted magnesium with hydrochloric acid and tested the pH of the solution at the beginning and at the end. My pH paper told me that the pH did not change or at least very ...
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2answers
44 views

Why does bond breaking in ATP release energy? [duplicate]

We always come across that formation of bonds releases energy, and bond breaking requires energy, but in the case where ATP converts into ADP or AMP (bond breaking), energy is released. Why? Further, ...
3
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1answer
10k views

What properties does a solvent with a high dielectric constant have?

My professor commented that water has a higher dielectric constant than alcohol. Okay, but on what basis? He didn't elaborate; he asked us which one seemed "more electric" and most answered water. ...
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2answers
31 views

what is the exact meaning of oxidation state? [duplicate]

can you mention the concept of oxidation state without its simple definition i-e it is the apparent charge +ve or -ve.....😪 I found these in wikipedia but didn't understand."Conceptually, the ...
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0answers
26 views

How much does steam expand in relation to its temperature (assuming starting at 100 °C) and constant pressure in a flexible container? Thanks! [on hold]

How much does steam expand in relation to its temperature (assuming starting at 100 °C) and constant pressure in a flexible container? For example, if 1 L of $\ce{H2O}$ expands to about 1600× the ...
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0answers
17 views

Bond Nature of a comound [on hold]

How can we determine the type of Bond in LiBaPO4? can we find out the nature of bond through charge transfer values of these elements? if yes then how?
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2answers
43 views

Why enthalpy is defined at a constant pressure?

How absolute enthalpy and enthalpy change are defined? What is the clear difference between enthalpy and heat? Is it the constancy of pressure what makes the enthalpy a state function? My teacher ...
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0answers
20 views

Why concentration of water is not taken 1 for the equilibrium constant of esterification reaction? [on hold]

For pure liquids and pure gases, we approximate the concentrations equal to 1. In case of the esterification reaction, why do we write $\ce{H2O(l)}$ in the $K_\mathrm{c}$ formula since we have ...
1
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1answer
25 views

adiabatic expansion vs Joule-Thomson Effect

Source: The1stLawofThermodynamicsLesson4 I am looking for difference between adiabatic expansion and Joule-Thomson effect. Looking at the setup demonstrating Joule-Thomson effect, I find no essential ...
3
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2answers
573 views

Plot of Arrhenius Equation with temperature

I saw the following plot of the Arrhenius Equation on Wikipedia (cc-by Zivilverteidigung and Matthias M.). It is a concave upwards graph, but according to the equation $$k= A \mathrm e^\frac{-E_\...
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0answers
16 views

Schrodinger Equation : TDSE and TISE [closed]

How can one particular Schrodinger equation be both time-dependent and time-independent at the same time? I mean its wrong by the very notion to say both simultaneously. We encounter many instances ...
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0answers
16 views

Can you please tell me the process? [closed]

The value of Kc=4.24 at 800K for the reaction, CO(g)+ H20(g) >CO2(g) + H2(g) Calculate the equilibrium concentrations of CO2, H2, CO and H2O at 800K, if only CO and H2O are present initially at ...
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1answer
26 views

Pls help confusing [closed]

Its a chemical kinetics quedtion from jee main 2019 i got answer 10 but many places answer is 5 i thought that as reaction is first order it must be equal to half life
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3answers
2k views

Why does calcium oxide react with sulfur dioxide?

Which of the following compounds reacts with calcium oxide, $\ce{CaO}$? (a) $\ce{K2O}$ (b) $\ce{Na2O}$ (c) $\ce{SO2}$ (d) $\ce{MgO}$ I thought that since sodium is higher in the reactivity ...
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0answers
12 views

To find out how much urea will separate out? [closed]

I know how to solve the above question I will let water used be 'w' gm and then will apply the formula of decrease in free zing point and then calculate 'w' then it would be subtracted from 250 gm . ...
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0answers
15 views

In dS≥dQ/T, material equilibrium means that there is not material changes at all or that a material change can be reversible and at equilibrium?

I am reading Levine's Physical Chemistry, I know how to arrive to that equation, but I have questions. First, $\mathrm{d}S=\mathrm{d}Q/T$ for material equilibrium, but if there is a heat flow I ...
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0answers
14 views

what is the difference between oxidation state, charge and valency? [duplicate]

Is there any specific atom or compound or molecule possessing oxidation state different from charge and valency, so that we can clearly understand the difference between the three.
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4answers
3k views

Does any known substance ignite on cooling?

As the title says, I'm interested in knowing if there is any substance — or combination of substances — that ignites (or even increases its chance of spontaneous ignition) when cooled. I've never ...
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0answers
44 views

heat produced to make Fe [on hold]

For production of pure iron from $\ce{Fe2O3}$, a factory is mixing carbon monoxide with this iron oxide. Given the information below and assuming the yield 100%, how many kilowatt hours would be ...
0
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0answers
14 views

How do I make a 0.5 M citrate buffer at pH 4.5?

I need to make a citrate-sodium citrate buffer at 0.5 M concentration and pH 4.5. I calculated the molarities of the citrate and disodium citrate based on the Henderson Hasselbalch equation, using a ...
5
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2answers
201 views

The difference between elementary and concerted reactions

In the IUPAC Gold Book: elementary reactionA reaction for which no reaction intermediates have been detected or need to be postulated in order to describe the chemical reaction ...
4
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1answer
35 views

How to specify atomic carbon terms in the coupled and uncoupled representation?

So, we know, that the atomic carbon in the electronic configuration $1s^22s^22p^2$ has the following terms $${}^1S, {}^1D, {}^3P$$ My question is - how can I correctly specify these terms in the ...
2
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6answers
3k views

Storage of Urine

Not all may be favorable to this project, but I will explain what I am trying to do. I work at home, and instead of walking a moderate distance to the bathroom and loosing my focus, I've been, at ...
2
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1answer
27 views

Difference between adiabatic and nonadiabatic tunneling for molecule

What is the difference between adiabatic and nonadiabatic tunneling for a molecule in a laser-field? Does nonadiabatic tunneling necessarily relate to the Conical intersection or curve-crossing?
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3answers
7k views

Can you heat water with additives?

I have been curious about this question for a while. If you want to warm up a large amount of water, is it feasible to do this by adding a substance that has an exothermic reaction with the water? ...
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3answers
154 views

Why is the enthalpy of a reaction equal to the difference between the enthalpies of combustion of the reactants and the products?

My textbook gives me the following formula for calculating the enthalpy change of any reaction: $$\Delta H_\mathrm{r}^\circ=\sum(\Delta H_\mathrm{c}^\circ)_\text{reactants}-\sum(\Delta H_\mathrm{c}^\...
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1answer
32 views

Why is excluded volume in van der Waals equation divided by 2?

Source: Physics Stack Exchange The excluded volume calculated based on the diagram is 8 times the volume of a molecule. The volume is then divided by 2 to give the so-called excluded volume per ...
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0answers
10 views

How to calculate pollutant mass concentration in exhaust air?

I want to calculate the mass concentration of methane in exhaust air as unit gram per cubic meter per hour. Assumed we have the following situation: A bioreactor ...
4
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1answer
41 views

Compressibility Factor Graph - Which gas attains a deeper minimum?

As in the given graph, how do I predict which curve among that of hydrogen, methane, and carbon dioxide attains a deeper absolute minimum? (greater deviation from Z=1). In fact, how do I make this ...
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0answers
21 views

Why do some cations and anions interact with water to form corrresponding acids and bases(hydrolysis)? [duplicate]

I have seen in my textbook that on cations/anions formed on ionization of salts either exist as hydrated salts in aqueous solutions or interact with water to reform corresponding acids/bases depending ...
5
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1answer
51 views

How is a NMR spectrum obtained?

I am reading about NMR, and from what I'm understanding it should give information on the transition energies in the spectrum of the nuclear spin in a magnetic field. What I don't understand is how ...
0
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1answer
66 views

What is the radius of the atoms? [closed]

In a recipient there is an unknown monoatomic gas that occupies a volume of $\pu{230 cm3}$, at $\pu{300 K}$ and $\pu{1 atm}$. It is known that the atoms occupy a volume of $2\times10^{-4}$. Find the ...
5
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1answer
3k views

Does a gold detector exist?

I see many sites that claim to sell working gold detectors but I am not convinced that they work. Also, does a metal detector detect gold?
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1answer
39 views

What are good examples of questions that make college students think about chemistry concepts? [closed]

I am teaching the second semester of general chemistry at the college level. The course tends to get bogged down in calculations, and sometimes we forget about the big picture and what is going on at ...
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2answers
37 views

Intuitive explanation for depression of freezing point

Why does depression of freezing point takes place if a non-volatile solute is added to the solution? For more details about the question checkout this link below Depression of freezing point
5
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1answer
109 views

Using thermodynamics to predict the acid-base character of fluoride ion in water

I was working through the end-of-chapter exercises of the acid-base chapter in Shriver's Inorganic Chemistry when I came across the following problem: 4.7. The effective proton affinity $\ce{A^{'}_{...
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1answer
7k views

Differences between chemical physics and physical chemistry?

What makes these two seemingly identical topics separate? What does each field more focus on, like do chemical physics researchers study more the atomic/molecular interactions while the physical ...
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2answers
50 views

Why are reversible reactions spontaneous?

If a reversible chemical reaction is spontaneous in one direction, shouldn't it be non spontaneous $(ΔG > 0)$ in the other? In other words for the reaction: $$\ce{A + B ⇌ C + D}$$ if $$\ce{A + B ...
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4answers
1k views

Relation between chemical kinetics and chemical equilibrium

In my chemistry book, the law of chemical equilibrium is derived from the law of mass action: For a reversible chemical reaction $$\ce{aA +bB\rightleftharpoons cC + dD}$$ where $a$, $b$, $c$ and $d$...
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1answer
45 views

Is delta S the same in reversible and irreversible processes?

I've read that change in entropy of a system is the same for a system in reversible and irreversible processes since it is a state function and does not depend on the pathway. Does this only apply to ...
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2answers
48 views

Exact meaning of constant volume heat capacity

From Wikipedia: $$ \left(\frac{\partial U}{\partial T}\right)_V = \left(\frac{\partial Q}{\partial T}\right)_V = C_V, $$ $C_V$ is what known to be constant volume heat capacity. I don't really get ...