# 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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### During phase change in matter, why doesn't the temperature change?

I was working on something in school and came across the question: Why does the temperature not change much during a phase change? I'm really not sure why this happens in matter and I couldn't ...
26 views

### Dissolving Time Function for Concrete

So I was just exploring some ideas on my own and am having trouble analytically solving the following: Let $D(n,m,T)$ be the time it takes to dissolve an n x n x n cube of concrete in m molar HcL at ...
12k views

### Determining if reaction is endothermic or exothermic using equilbrium constant

For the following reaction: $$\ce{W_{(s)} + 4 Br_{(g)} <=> WBr4_{(g)}}$$ At 900 K, $K_\mathrm{p}=100$ and at 2800 K, $K_\mathrm{p}=5$. At higher temperatures, the equilibrium has shifted ...
122 views

### Addition of combined gas law constant

There are two containers connected to each other but separated by a cork. If container(1) has a gas $G_1$ at a volume $V_1$, pressure $P_1$ and temperature $T_1$ and similarly in container(2) there ...
234 views

### How does the vacuum in atoms persist?

From very elementary chemistry I understand that atoms are mostly empty space, with a few tiny little objects whizzing around. There must then be a vacuum in between these particles. I always thought ...
9k views

### The difference between heat of reaction at constant pressure and that at constant volume

If supposing the kp value of a reaction is 10 Atm at 300K and 4atm at 400K. Then how can we say that the difference between the heat of reaction at constant pressure and that at constant volume is RT ...
7k views

### What are the standard math prerequisites for physical chemistry? [closed]

I'm currently a chemistry major and I know that physical chemistry requires lots of calculus. Which mathematics courses should I take so that I am well prepared for my physical chemistry courses? ...
2k views

### 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 ...
9k 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 ...
2k views

### Can a mixture of water miscible solvent and water be separated by fractional freezing on a dry ice bath?

If a mixture of water with acetone, methanol, ethanol, or other water miscible solvent, is cooled below 0 degrees, would the water freeze and aggregate out as ice, separating out of the mixture. Or ...
510 views

### How does the Freezing Point fall in a solution?

It is known that addition of a non-volatile solute to a volatile solvent(liquid) to give a solution reduces the Vapour Pressure of the solution (well solvent actually as only solvent is volatile). ...
4k views

### Which one, Mulliken charge distribution and NBO, is more reliable?

Sometimes the Mulliken and NBO turn out to be so different that I can't decide which one I can trust. I've heard that Mulliken is inaccurate, but is NBO always accurate? And should I use Gaussian or ...
429 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 ...
902 views

### Applying the Le Chatelier principle

I am having issues understanding the consequence(s) of a decrease in pressure on a chemical reaction. I have understood that when we increase the pressure, the side having more number of moles wants ...
326 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 right-...
110 views

### Residual stress in polymer coatings

A paper talks about the residual stress when coating polymers. It says that residual stress is the sum of the "heat stress" (due to the difference in thermal expansion coefficients) and the "shrinkage ...
5k views

### How to calculate the equilibrium composition after a change in partial pressure of one component?

Question Ammonium carbamate dissociates as shown below. $$\ce{NH2COONH4 (s) -> 2NH3 (g) + CO2 (g)}$$ In a closed vessel containing ammonium carbamate in equilibrium with ammonia and carbon ...
11k 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. ...
106 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. $K_\mathrm c$ for the ...
453 views

### Auto ionization of water and evaporation of water

I know that the heating of water drives the auto ionization of water. It also drives the evaporation of water. My question is where do the ions go as the water evaporates as it is heated up. Ions can'...
211 views

### If dark surfaces absorb/store more light/energy than light surfaces, then does dark skin, on average, store energy from light most efficiently?

If darker surfaces absorb/store more light/energy per square inch than light surfaces, then does dark skin, on average, store energy more efficiently than light skin? (edited).
2k views

### Explaining Ionization to kids

I have a quest to explain a physical, chemical theory to kids of age 8-12. The topic is "Ionization". We all understand from early experiments of Physics and Chemistry (the Millikan oil drop ...
982 views

Why are peroxide linkages generally weak? Is it due to Coulombic repulsions? I can't see how placing two oxygens with high degrees of partial negative character next to each other is a good thing in ...
2k views

### Nitrogen dioxide dimerization

$\ce{NO}$ can't dimerize and that is explained because the free electron is in an antibonding orbital. The same is true for $\ce{NO2}$, but it can dimerize, how?
6k views

### Why can't light pass through a gold foil, but alpha particles can?

Rutherfords experiment showed that most of the alpha particles passed through a thin gold foil undeflected. So why can't light pass through the foil, which is supposedly thinner than the heavy alpha ...
3k views

### How can two electrons lie together in an orbital?

Two electron of opposite spin can lie in a single orbital.. But what about the electron-electron repulsion. Okay! I got that the nuclear charge rather the large Z-effective overcome this repulsion by ...
5k views

### Difference between actual position of electron and Radial Distribution Probability

Its known that the radius of maximum probability of 2s orbitals is more than that of 2p orbitals. It means that the maximum probability of finding an electron in an 2s is further away from electron ...
27k views

### How to figure out which phase on a phase diagram will be the most dense?

If I am given a phase diagram, how can I determine which phase will have more density? What should I consider to solve these kinds of questions? Does the answer have to do with the area that each ...
144 views

### Proteins and their solubility

I have 2 statements , and i am not sure, whether they are true or false. Proteins like albumin and haemoglobin are insoluble in water (in my view , almost all proteins are soluble- so this is a ...
114 views

### What is the Solubility of Common Noble Gases in Concentrated Phosphoric Acid, 85% w/v?

By Henry’s Law, the concentration of a dissolving gas in a liquid is proportional to the partial pressure of that gas in contact with the liquid, mathematically, $p = k_\mathrm{H} c$, where $p$ is ...
186 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 ...
331 views

### Are forming coins starting with sodium chloride possible without the clay melting from the molten metal?

Is forming metal coins (specifically ones with copper, nickel, and zinc) possible with these steps: Carve a sheet of sodium chloride so that it is big but not too big and so that the design sticks ...
1k views

### The highest melting point

Inspired by this question, what is the substance or compound with the highest melting point? At standard atmospheric pressure and ever-increasing temperature which substance a) eventually becomes ...
70k views

### How to calculate which ionic compound has the highest melting point?

Which of the following compounds has the highest melting point: $\ce{PCl5}$, $\ce{H2O}$, $\ce{NaCl}$, $\ce{SrCl2}$, $\ce{CaF2}$? In general, ionic compounds will have higher boiling points than those ...
16k views

### Is melting of gold a physical property?

I read that melting of gold is a physical property, but I wonder if this is true. If we want to melt gold we will need to add heat, and once we add heat to gold to melt it, there must be a chemical ...
888 views

### Corrosion of metals and observations in the agar medium?

I want to know which metals oxidize and which is reduced and changes in medium and observations? According to my knowledge more corrosion will take place in Zn and Fe also corrode. Then copper should ...
29k 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. $$\Delta E=q+w$$
2k views

### Is sublimation a property of all substances?

I wonder if sublimation can be done only on certain substances like iodine, or it can be done on all substances. In other words, can sublimation be done, for example, on water? If it cannot, then why?...
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### Structure of fluoroalkylsilane

I want to use FAS (fluoroalkylsilane) in my molecular dynamics study. How can I find it's real structure? So that I can find proper forcefield for simulating the molecule. It would be very nice if you ...
9k views

### What are the fumes that form above liquid nitrogen?

What is the composition of liquid nitrogen fumes? Is direct contact with these fumes harmful?
5k views

### Finding orbit radius using the Bohr model and Rydberg equation

To start with its a homework problem, quite lengthy. A particle of mass equal to 208 times the mass of an electron moves in a circular orbit around a nucleus of charge $+3e$. Assuming the Bohr ...
2k views

### Advanced Level Chemistry Book Recommendation [duplicate]

I have a test comming up on Chemistry in Advanced Level and I sincerly ask for a book recommendation for chemistry. I already got the book chemistry by Ramond Chang. And I am pretty near to the exam. ...
825 views

### Is the E in Arrhenius equation the change of enthalpy?

I'd like to know whether the activation energy in Arrhenius equation is the enthalpy difference between the transition state and the reactant. If it's not enthalpy, is it Gibbs energy or something ...
5k views

### How can I determine the chemical composition of local rocks and minerals?

Specifically I live in the U.S. so I'm asking about an ordinary rock that you might find in your backyard or near a playground. Humans have discovered gun powder, petroleum, silica, iron, and many ...
14k views

### Acid-base equilibrium of NH4CN

I'm having difficulties understanding this problem. We have in the problem that $K_\mathrm a$ for $\ce{HCN} = 6.2\cdot10^{-10}$ and $K_\mathrm b$ for $\ce{NH3} = 1.8\cdot10^{-5}$. Write chemical ...
922 views

### On Heisenberg's uncertainty principle

Why can't we find the exact position and velocity of a particle? And why is it that if the uncertainty in position is very, very large then the velocity can be determined, and vice versa? Please ...
1k views

### Is there a reason for the mathematical form of the equilibrium constant? [duplicate]

Why are the two molarities multiplied and not added, and why is each raised to the power of the coefficient rather than multiplied by it? What is the reasoning behind this form? Was it simply ...
2k views

### How to use molality and molarity to determine the molar mass of a compound?

An aqueous solution of a certain organic compound has a density of $1.063~\mathrm{g/mL}$, an osmotic pressure of $12.16~\mathrm{atm}$ at $25.0~\mathrm{^\circ{}C}$, and a freezing point of \$-1.03~\...