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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170 views

Nature of transition metals [duplicate]

The transition metals have valence and penultimate shell incompletely filled . so does this mean that the transition metals first fill up their valence shell and then penultimate shell?
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The last element's atomic number

I was just thinking what can be the last atomic number that can exist within the range of permissible radioactivity limit and considering all other factors in quantum physics and chemical factors.
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What is the differences between partial pressure and vapour pressure?

Was looking at Henry's law and Raoult's law constants and there seemto be lots of equations involved. Henry's law involves partial pressure and the latter involves the vapor pressure. Wondering what ...
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To which state of matter does the flame belong to?

I had this question from the day (9 years old, now 16) that I learned about states of matter. I have asked many of my teachers, some of them told me it's a gas some that it's a plasma. Can anyone ...
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What is the nature and character of fire? [duplicate]

What is fire? Is it a material or energy or something else? Please explain it to me. My friend asked me this. I am stuck with this problem.
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Why is the pressure value altered in this gas law numerical?

When I work through the following problem it is unclear to me why 0.00120 mmHg is converted to 0.00332 mmHg. What is the temperature of 0.00332 g of mercury in the gas phase with pressure of 0....
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How do I determine crystal field splitting (for example, for [Ni(CO)4])?

How to know how many electrons are there in $T_{2g}$ and $E_g$ orbitals? I think rather than a broad answer, an example would help. So, consider the compound $\ce{Ni(CO)4}$ and how to calculate CFSE ...
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What is the pKa Range for weak acids and bases?

Am I correct in assuming that the following is true? $\mathrm pK_\mathrm a < 3$ is for a strong acid $3 < \mathrm pK_\mathrm a < 7$ is for a weak acid $7 < \mathrm pK_\mathrm a < 11$ ...
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1answer
221 views

What can I use as a sacrificial electrode to stop the oxidation of aluminium?

For a solution of chromimum phosphate when putting in to solution aluminum there is removal of the aluminum. It is possible to prevent a galvanic cell, stop the etching of the aluminum, by putting ...
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Alternatives to Ring Stands

I'm trying to find an alternative to simple ring stands to hold a simple electrochemical cell. The issue is that it is difficult to adjust the height to the right position to within even a couple ...
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Do the compounds NaₓIrO₂ and NaOsO₂ exist?

Based on some physics background, I want to know whether have scientists synthesized these two materials: $\ce{Na_{$x$}IrO2}$ and $\ce{NaOsO2}$ in the lab, if so, what properties do they have? I ...
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Ideal gas derivations

For an ideal gas, how can someone obtain this: $$ \bar{V}dP = RdT- P \bar{dV}$$ from which it can de deducted, that for a constant temperature $$ \frac{dP}{\bar{dV}} = -RT $$
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What type of sensor technologies exist to determine the chemical composition of a polymer?

Let's say I have several pieces of trash and each is made with a different type of material like: Plastic bottle : High Density Polyethylene (HDPE) Cereal box : Paperboard & Epichlorohydrin ...
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Why does ZnO turn yellow when it is hot?

Why does ZnO's color become yellow when it is hot? I have read that it is because of physical properties, but I need a more elaborate explanation.
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How do I distinguish between internal energy and enthalpy?

I am finding it hard to distinguish between the two. Can someone explain the two terms and the difference between them? I tried learning from Wikipedia, but it said for both the above terms that it ...
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Why is the enthalpy change not zero in an adiabatic process?

Which of the following must be true for adiabatic processes? $C_\mathrm{V} = C_\mathrm{p}$ $\Delta H = 0$ $\Delta U = 0$ $\Delta S = 0$ $q = 0$ (Source: Chemistry GRE) The answer ...
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Could micrograms of polonium really change the viscosity of a whole teapot?

I was reading How radioactive poison became the assassin’s weapon of choice and it opens describing how The men eventually left, and Andrade cleared the table. As he poured the remaining tea away, ...
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What makes substances explosive

Can someone explain clearly to me why some things are explosive?
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Why do bubbles form when it rains?

I noticed sometime ago that bubbles formed in puddles/streets whenever it rained. I am wondering if someone could tell me what could cause such bubbles. I examined the bubbles again today more closely ...
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Can an aqueous solution conduct electricity forever?

We know that pure water does not conduct electricity, but salt water is a decent conductor. This is commonly explained by saying that “the ions carry the current through the solution”, which is an ...
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Viscosity of two different solutions

Suppose that I have 10 kg of plastic/polymer that is non solvable in water. I then divide the plastic/polymer into two equal parts. Let us name the parts A and B in order to identify them. I then ...
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Is it realistic to have a natural oxygen source in a cave?

Is it realistic to have a natural oxygen source in a cave? I am writing a story, about people who live underground in a land that is freezing outside. Heat is taken care of by geothermally heated ...
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246 views

What is chemical free energy?

What is chemical free energy? How can we practically explain its existence? How can it be used to do some useful work like in an electrochemical cell? I couldn't understand clearly about it when I ...
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What is the most rare element in periodic table

What is the most rare element in periodic table? I have a lot of confusion about this.
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Calculating Standard Gibbs Energy of Dissolution

The solubility of mercury (I) iodide is $\mathrm{5.5\ fmol/L}$ in water at $25\ \mathrm{^\circ C}$. What is the standard Gibbs energy of dissolution of the salt? The reaction is $$\ce{Hg2I2(s) -&...
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Is it possible to make liquid nitrogen with a bottle of CO2 gas and a freezer?

I really want to make liquid nitrogen(or oxygen) without using dry ice, a specially made freezer, or other chemicals. I have a mixture of some sponges, rotten grass, sugar and water, which makes ...
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Melting points and boiling points of primary alcohols do not follow the same trend

If one considers boiling points (in °C) of primary alcohols, one finds the following: methanol: 65 ethanol: 79 1-propanol: 97 1-butanol: 117 1-pentanol: 138 This trend is due to Van der Waals forces ...
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Difference between reversible and irreversible thermodynamic process

I have been reading up (on this website) about the difference between reversible and irreversible thermodynamic process and it defines them saying that reversible processes are ideal processes while ...
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Ideal Gas Law, P,T,V Change => adiabatic?

Given the expansion of an ideal gas, Pressure $P$, Volume $V$ and Temperature $T$ change from $P_1$, $V_1$, $T_1$, to $P_2$, $V_2$, $T_2$. a) Does the standard ideal gas law predict correct end ...
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Why do amorphous substances have different values of physical properties in different directions?

Today my teacher taught about amorphous and crystalline substances. Crystalline substances are said to have different values for physical properties (like speed of light, electrical resistance, etc) ...
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Gas law and moles

A sample of solid magnesium reacts with excess $\ce{HCl}$ solution to form hydrogen gas. The sample of gas measures $1.628\ \mathrm{L}$ at $22.0\ \mathrm{^\circ C}$ and $0.930\ \mathrm{atm}$ of ...
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252 views

Calculate partial pressure of gases at equilibrium

I have the reaction $\ce{CO_{(g)} + Cl2_{(g)} <=> COCl2_{(g)}}$ where $K=4.5\times10^9$ at $100\ \mathrm{^\circ C}$ The first question was to find $K_p$ which I know is $K_p=K(RT)^{\Delta n}$ ...
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Concentrations at equililibrium

At $25 ^\circ C$, $K=0.090$ for the reaction $$\ce{H2O (g) + Cl2O (g) -> 2HOCl (g)}$$ calculate the concentrations of all species at equilibrium for the case: $\pu{1.0 g} \ce{H2O}$ and $\pu{2....
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What is the edge of a diamond like?

The chemical structure of a diamond is defined as an endless lattice in which each carbon atom is covalently bonded to four other carbon atoms situated at the four ends of a tetrahedron. But of ...
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Isothermal vs. adiabatic compression of gas in terms of required energy

I am working on an instruction manual of sorts to be used with an introductory course in thermodynamics. As an example of problem solving, I attempt to answer the following question: If you have ...
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Calculating charge on amino acid from pKa

I have been given $\mathrm pK_\mathrm a$ values of an amino group, a carboxyl group and a side chain of cysteine. How can I find the ionic charge on it at different $\mathrm{pH}$ values?
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Strong acid equilibrium

So a teacher at school told me that strong acids do not create an equilibrium in general, while weak acids do (thats the difference, strong acids namely ionize completely). However, I lately stumbled ...
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Why is Charcoal such an excellent adsorbent?

Charcoal (also activated charcoal) is known to adsorb a huge variety of substances including a variety of paints, dyes and many different kinds of ions. Moreover, the amount of adsorption at normal ...
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Why are wave functions orthogonal?

It seems that all wave functions studied in physical chemistry are orthogonal (e.g. particle in a box, hydrogen atomic orbitals). Does this come about because we purposefully make them orthogonal, or ...
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How does molecular orbital overlap affect energy?

If there is more overlap of the same sign wave function, this apparently leads to lower energy. I don't understand why. My professor said that there would be fewer nodes, and fewer nodes means lower ...
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Magnetic moment of coordination complexes?

To understand the commonly quoted magnetic values of coordination complexes (central ion) we use $$m_l=\sqrt{n(n+2)} \text{BM where BM}=\frac{e\hbar}{2m_e}\text{JT}^{-1}$$ $n$=number of unpaired ...
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Why do branched chain compounds have lower boiling points than the corresponding straight chain isomers?

The branched chain compounds have lower boiling points than the corresponding straight chain isomers. For example, $\ce{CH_3CH_2CH_2CH_2CH_3}$ - No branching-Pentane (n-pentane) ($\mathrm{...
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Mathematical basis of why enthalpy of mixing is 0 for ideal gas

For this case, let's say there are two identical chambers connected by a small tube, constant pressure and temperature. There's a closed valve that separates the two chambers. Within the chambers ...
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Speed of ionic reactions?

Why are ionic reactions extremely fast, as compared to other gaseous reactions? The ionic reactions (precipitations, neutralizations etc.) are extremely fast (somewhere about $10^{12}$ times ...
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Why do hairs (rubbed with plastic comb) fallen on water seems to be sticking?

I was observing from many days, how hairs seems to be sticking to water, when made to fall on it. I made an attempt to know what really was going on. I kept a jug of stationary water under the light, ...
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1answer
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How to determine whether a compound is gas or liquid or solid? [closed]

My book says, methyl chloride, methyl bromide, ethyl chloride and some cholorofluromethanes are gases at room temperature, whereas higher members are liquids or solids. Why? With this question, I ...
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Why do puffed rice stick to wet hands?

My mom gave puffed rice to eat, I had quite wet hands. I saw that, each puffed rice pieces started hanging to the hand, when I brought my hand in contact with them. I thought about electrostatics ...
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Why do liquid crystal displays (LCDs) visually distort under pressure?

A venerable question, as old as LCDs themselves. I assume it has something to do with pressure-induced changes in the path length across the display, but that's just a guess. Of particular interest to ...
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A function for getting the nuclide's nuclear binding energy?

Is there a function $f(A)$ or $f(Z, A)$ that gets the energy of nuclear binding of one nuclide in atom? Or other way to get it? My chemistry book says only to get it from the chart which is very ...