We’re rewarding the question askers & reputations are being recalculated! Read more.

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.

Filter by
Sorted by
Tagged with
2
votes
0answers
16 views

Why do electrocatalysts based on polyoxometalates and carbon materials have a weaker activity/performance in acidic media?

I am testing now some doped N and S doped carbon nanomaterials alone and immobilized in POM for the purpose of developing a nanocomposite that can serve as an electrocatalyst for energy-related ...
0
votes
0answers
24 views

how does mass of carbon 12 is like this? [duplicate]

1u is defined as per carbon 12 so 1 atom of c have 6 neutrons and 6 protons both having mass more than 1u (Google)so total mass of carbon 12 is more then 12u (also there would be some mass of ...
1
vote
0answers
19 views

Why do polyoxometalates have good electrochemical/ redox properties?

Many authors are using polyoxomethalates immobilised in carbon nanomaterial as electrocatalysts for energy related reactions (ORR, HER, OER). Other metal alloys have also shown to be successful as ...
1
vote
0answers
20 views

What are the reasons that make platinum a good electrocatalyst for oxygen reduction reaction? [duplicate]

Researchers are trying to find new electrocatalysts for energy related reactions in fuel cells in order to replace the expensive platinum-based materials. I would like to know what are exactly the ...
0
votes
1answer
120 views

Hydrolysis and Hydration

Does Ammonium Acetate, a salt of a weak base and weak acid, undergo both hydration and hydrolysis in aqeous solution? What is meant by the statement that " Some hydration reactions are hydrolysis"
0
votes
2answers
370 views

Equilibrium constant for esterification process

Teacher told us that the concentration term for pure liquids and solids is always $1$. But online I found this reaction: $$\ce{CH3COOH(l) + CH3CH2OH(l) <=> CH3COOCH2CH3(l) + H2O(l)}$$ ...
4
votes
3answers
346 views

No sign flipping while figuring out the emf of voltaic cell?

I learnt that for a voltaic cell, the value for the $E_\text{cell}^\circ$ when the reaction is spontaneous is given by $$E_\text{cell}^\circ = E_\text{cathode}^\circ - E_\text{anode}^\circ, \label{...
3
votes
1answer
176 views

Gibbs free energy of formation vs. Gibbs free energy of reaction?

Consider the following reaction: $$\ce{A(s) + B(s) <=> AB(s)}.$$ I know there might be kinetic limitations but I am only interested in thermodynamic relations. In general, the Gibbs free ...
1
vote
1answer
29 views

Should I include ions from the solvent in solubility product constant calculations?

I'm trying to determine the Solubility Constant $K_\mathrm{sp}$ of $\ce{Ba(NO3)2}$ dissolved in nitric acid solution $\ce{HNO3}$ from experimental data. $\ce{HNO3}$ will be mostly dissociated so ...
1
vote
2answers
70 views

Why is nucleus charge squared in Rydbergs formula?

According to coulumbs law, the energy changes linearly with charge. So why is the nucleus charge squared in this formula? Is there a way to derive it? I was suspecting it might be because it pulls ...
0
votes
0answers
113 views

Can a solute be physically filtered out of a solvent?

Suppose that I have a substance dissolved in water. I then pour the solution into a filter. The filter's pores are large enough to allow the passage of water, but not the passage of the substance. In ...
2
votes
0answers
160 views

What is the ANO-RCC basis set and how does it work?

On the basis set exchange, the ANO-RCC basis looks huge, even for hydrogen: ...
0
votes
2answers
71 views

Trend in ionisation potential in period 2

Carbon has valence electronic configuration of $2s^2$ $2p^2$. Beryllium has configuration $2s^2$.So carbon should have less ionisation potential than Beryllium as it is easier to remove electrons from ...
0
votes
2answers
117 views

Find out of the friend is getting a good deal [closed]

I have a strange chemistry question that I've never came across before, and I have no idea about how to solve it. Your friend comes across a good deal to purchase a gold ring. She asks you for ...
1
vote
1answer
39 views

Which ions determine ionic conductivity of a salt solution?

Let's take $\ce{ZnSO4}$ salt solution in water for example. So the ions inside my solution will be $\ce{H+}$, $\ce{OH-}$, $\ce{Zn^2+}$ and $\ce{SO4^2-}$. My questions are: Is the ionic conductivity ...
1
vote
0answers
29 views

Freezing point lowering for a mixture of many liquids

I have been taught that if I have a solute of molality $m$ mixed with a liquid, the freezing point in lowered by an amount $K_\mathrm{f}\cdot m$ where $K_\mathrm{f}$ is the molal freezing depression ...
2
votes
1answer
192 views

How dependent is the molal depression constant on the nature of solute?

I've been reading about the molal depression constant (freezing point depression constant) for binary solutions in class. I encountered a problem (see below) in which the constant $K_f$ was to be ...
2
votes
2answers
372 views

Gibbs free energy in standard state vs. equilibrium

I have a problem with the definition of the standard Gibbs energy and its connection to the equilibrium constants. I think, that I've basically understood what the different equation mean but there ...
1
vote
0answers
205 views

Conversion of graphite into diamond [duplicate]

The standard state Gibbs free energies of formation of C(graphite) and C(diamond) at $T = \pu{298 K}$ are $\pu{0 kJ mol-1}$ and $\pu{2.9 kJ mol-1}$, respectively. The conversion of graphite [C(...
-1
votes
1answer
119 views

Is there a error at page 566 of Atkins Physical Chemistry? [closed]

At page 556 I found this question being analyzed and the rate law is provided. However, when I apply steady state approximation, I can't find the result without the factor 2. Is it me being wrong?
1
vote
2answers
85 views

Ionic equilibrium between multiple ions

This is a question from IIT-JEE 1993: For the reaction $$\ce{[Ag(CN)2]^- -> Ag^+ + 2CN^-}$$ the equilibrium constant at $\pu{298 K}$ is $\pu{4e-10}$. The silver ion concentration in a ...
7
votes
1answer
123 views

What could cause a peak to split into 2 resonances as temperature increases in NMR spectroscopy

I understand that some peaks may coalesce upon an increase in temperature due to an increase in free rotation, this does occur with some peaks in my data. Why might you see a peak split into two other ...
9
votes
0answers
210 views

What is the largest coupled cluster calculation that has ever been done (as of March 2019)?

I am doing some research and trying to make sure the numbers I am reporting are accurate. I found that the paper by Sylvetsky et. al. says:[1] We were, however, able to complete a ...
5
votes
1answer
142 views

Energy of photons of given frequency and number

I’m having trouble with calculating the energy of $\pu{5.00e10}$ photons of frequency $\pu{1.00e9 s-1}$. I know that to calculate the energy $E = hf$ is to be used. However, I am unaware as to what ...
5
votes
4answers
668 views

Why does the degree of dissociation change when we dilute a weak acid even though the equilibrium constant $K$ is constant?

$K$ represents the ratio of concentrations of molecules in a solution at equilibrium, which means that $Q_\mathrm{r}$ (that ratio at any given point) looks to be identical to $K$. In other words, the ...
0
votes
1answer
2k views

What is the maximum number of emission lines when the excited electron of a H atom in n = 6 drops to ground state?

When an electron in a higher energy state jumps to a lower energy state in Bohr’s model of hydrogen atom, it emits a photon which has energy equal to the difference in the energy between the final and ...
1
vote
1answer
24 views

Overall enthalpy balance on a mixing process

Let's say I have a mixing process involving $\ce{A}$ and $\ce{B}$ at temperatures $T_\ce{A}$ and $T_\ce{B}$, respectively. The $\ce{AB}$ mix is at temperature $T_p$. Our $ΔH_\mathrm{mix}$ is defined ...
7
votes
2answers
130 views

Feasibility and Entropy

Suppose you've got some reaction that has a positive $\Delta H$, and also has positive $\Delta S_\mathrm{sys}$. Due to the equation $$\Delta S_\mathrm{tot} = \Delta S_\mathrm{sys} - \frac{\Delta H}{T}$...
0
votes
1answer
129 views

if a balloon full of warm air was placed in a refrigerator, what is the result? [closed]

If a balloon full of warm air was placed in a refrigerator, What will happen to the Ballon ?
6
votes
2answers
398 views

What is a good source for large tables on the properties of water?

I'm currently doing an investigation for school on finding the Clausius-Clapeyron relation/gradient for boiling water and comparing it to the gradients along my line of best fit. It is given by the ...
3
votes
1answer
68 views

Minimizing energy of a molecule

I am minimizing energy of butane on the CHARMM Force Field and I am confused on how to go about getting a uniform unit for each different PE as in the potential energy for bond, angle, torsion, VDW, ...
1
vote
0answers
118 views

How to calculate the cell potential after the reaction has operated long enough for the Fe2+ to have changed by some concentration?

Consider the cell described below at $\pu{261 K}$: $$\ce{Fe | Fe^2+ (\pu{0.925 M}) || Cd^2+ (\pu{0.981 M}) | Cd}$$ Given $E^\circ_\ce{Cd^2+ -> Cd} = \pu{-0.403 V}$, $E^\circ_\ce{Fe^2+ -&...
-1
votes
1answer
57 views

Polyprotic Acid Titrations

Titrating a mixture of strong and weak acids will yield endpoints such that the volume of base required to reach each endpoint will be different for each acid, e.g. in a mixture of HCl and CH3COOH, ...
2
votes
1answer
156 views

Determining the reduction potential of a half cell reaction at a given pH

$E^\circ_\ce{Cu^2+|Cu} = \pu{0.34 V}$. What will be reduction potential at $\mathrm{pH} = 14$ for the same couple? Given that $K_\mathrm{sp}$ of $\ce{Cu(OH)2}$ is $10^{-19}$. My Attempt I think ...
0
votes
0answers
65 views

AP Chem Question about Reaction Rate - Confused?

I found this question in the AP Chem book, and I understand why B is the answer (as the answer key says). However, I don't understand why D is not also correct. The question is: A multistep reaction ...
2
votes
1answer
84 views

Cobalt electroplating over nickel-plated steel

From my research, I understand that cobalt can be used on top of a nickel layer to improve durability of the nickel plating on a steel object. I am using a nickel anode and nickel acetate as ...
13
votes
4answers
3k views

Why does liquid water form when we exhale on a mirror?

In the descriptions below, I always assume external pressure to be constant at 1 atm, the condition where daily observations are made. 1) When I exhale on a mirror, liquid water forms on the mirror. ...
1
vote
1answer
41 views

Why do reactions happen at all? [closed]

What makes some atoms/compounds reactive and some noble? What is the fundamental truth behind a reaction? It seems that two species can undergo number of combination to give a compound. Say Sodium and ...
2
votes
1answer
86 views

Shortcut method to find atomic term symbols ignoring the spin orbit coupling

Is there any shortcut method by which we can find the atomic term symbols ignoring the spin-orbit coupling, i.e. ignoring the values of J. For instance, when writing the d-d transitions for any ...
5
votes
0answers
189 views

Helmholtz double layer

I don't quite understand what is meant by the Helmholtz double layer. Textbooks states something along the lines of: the colloidal particles attain charge by selective adsorption, due to this it ...
0
votes
1answer
333 views

Why does the colour of gold sol change with particle size? [duplicate]

Regarding the colour of gold sol, my book says Finest gold sol is red in colour; as the size of particles increases, it appears purple, then blue and finally golden. This is the image I found on ...
1
vote
2answers
548 views

The respective speed of five molecules are 2, 1.5, 1.6, 1.6 and 1.2 km/s. The most probable speed in km/s will be?

The respective speed of five molecules are 2, 1.5, 1.6, 1.6 and 1.2 km/s. The most probable speed in km/s will be? 1. 2 2. 1.58 3. 1.6 4. 1.31 I think the answer should be 1.6 km/h but the ...
0
votes
1answer
146 views

Determination of pKb of a mono acidic base

$20$ mL of a weak monoacidic base($\text{BOH}$) requires $12$ mL of $0.3$ M $\text{HCl}$ solution for the equivalence point. During titration, the pH of the base solution was $10$ upon the addition of ...
2
votes
1answer
68 views

How do salt additives and impurities affect a critical micelle concentration?

So I understand that a CMC typically decreases as more salt additives are added. What I am not clear on is how exactly. The head groups are charged in this example (one anionic and one cationic) so ...
1
vote
1answer
1k views

Relation between electron gain enthalpy and electron affinity

The correct relation between electron gain enthalpy $(Δ_\mathrm{eg}H)$ and electron affinity $A_\mathrm{e}$ at any temperature '$T$' is A) $Δ_\mathrm{eg}H = -A_\mathrm{e} - \frac{5}{2}RT$ B) ...
4
votes
2answers
384 views

Lagrange Multipliers for the derivation of Maxwell-Boltzmann distribution

When deriving the MB-Distribution while taking the number of quantum states $g_j$ into account, the final equation I'd have to solve would be: $$\ln(g_j)-\ln(n_j)+\alpha+\beta\cdot E_j=0$$ Where $n_j$ ...
0
votes
2answers
131 views

Why is the rate of reaction calculated as d[A]/dt?

For example, for a simple chemical reaction like $$\ce{A -> C}$$ the rate of the reaction could be calculated as the rate of appearance of $\ce{C}$ or the disappearance of $\ce{A}$, which makes ...
1
vote
2answers
132 views

How to determine steady state of multi-step reaction with both reversible and irreversible steps?

I am trying to determine the relative concentrations of $\ce{U1}$, $\ce{U2}$, and $\ce{E}$ when the following reaction is at steady state. Note that $k_t$ is the zero order rate constant of new $\ce{...
-1
votes
1answer
31 views

What is the velocity of de Broglie wave?

Here is my calculation: note: $ν$ – frequency, $V$ – velocity of wave, $v'$– velocity of object. $$ \begin{align} λ &= h/mv' \tag{1}\\ mc^2/h &= ν \tag{2}\\ λν &= V \quad \text{(wave ...
0
votes
1answer
74 views

What are the effects of salt additives and impurities on the CMC? [closed]

I understand what a critical micelle concentration (CMC) is, however I do not know why or how impurities or salt additives affect it when measured in specific ways. Any help is much appreciated. So ...