The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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
6
votes
1answer
3k views

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) -&...
1
vote
1answer
343 views
0
votes
1answer
779 views

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 ...
2
votes
1answer
83k views

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 ...
4
votes
3answers
6k views

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 ...
1
vote
2answers
340 views

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 ...
1
vote
2answers
3k views

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) ...
0
votes
2answers
172 views

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 ...
0
votes
1answer
287 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 $K_p=K(RT)^{\Delta n}$ ...
0
votes
1answer
64 views

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....
19
votes
2answers
5k views

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 ...
9
votes
2answers
62k views

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 ...
8
votes
2answers
46k views

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?
3
votes
2answers
1k views

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 ...
14
votes
5answers
20k views

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 ...
3
votes
2answers
3k views

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 ...
3
votes
1answer
633 views

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 ...
2
votes
0answers
1k views

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 ...
22
votes
5answers
201k views

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{...
9
votes
1answer
1k views

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 ...
4
votes
3answers
5k views

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 ...
3
votes
2answers
942 views

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, ...
4
votes
1answer
32k views

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 ...
2
votes
2answers
366 views

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 ...
5
votes
1answer
3k views

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 ...
0
votes
2answers
69 views

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 ...
2
votes
0answers
84 views

Reference to find dielectric constants and dielectric relaxation time

I am working on a Master degree and need to know the following data : The static (low frequency) dielectric constant of isopropanol at 25 °C The Optical (high frequency) dielectric constant of ...
1
vote
1answer
973 views

The molar mass of aluminum by measuring the amount of hydrogen gas liberated when a sample of aluminum is treated with excess hydrochloric acid

This experiment involves the determination of the molar mass of aluminum by measuring the amount of hydrogen gas liberated when a sample of aluminum is treated with excess hydrochloric acid. In the ...
3
votes
1answer
733 views

What does HTO decay into?

I'm aware that tritium undergoes beta decay forming Helium-3. But in the case of HTO, what does it decay into? I don't suppose it decays into HeHO.
3
votes
1answer
1k views

Why does MgCl2 lower the freezing temperature, and how does it do so?

I am working on a project in my chemistry class, and even though we've already finished the lab, I'm still confused as to why and how $\ce{MgCl2}$ melts ice/ lowers the freezing temperature of water. ...
23
votes
2answers
10k views

Why does water dissociate to H3O+ and OH- rather than H+ and OH-?

Why does water dissociate to $\ce{H_{3}O^{+} + OH^{-}}$ instead of $\ce{H^{+} + OH^{-}}$? This question came to surface when I was learning about acids and bases, and learned this definition: $\...
1
vote
1answer
571 views

What is the solid crud that appears inside my kettle?

Almost every share-house I've lived in has had some nasty looking solids collecting inside. I always regret looking inside the kettle because a cup of tea never tastes quite as good after you've seen ...
1
vote
1answer
63 views

Is there a element that shows this pattern of boiling point?

Is there a compound that turns to gas at a certain temperature but if heated more turns back to liquid and if heated more than turn to gas? Does it exist naturally? Has a such a substance be found? ...
10
votes
1answer
2k views

Calculation of Atomic weight percentage in AAS

I am currently doing doping studies in a system similar to this ($\ce{A_{x}B_{1-x}}$) and I have to find atomic weight percentage of $\ce{B}$ element using atomic absorption spectroscopy(AAS). I have ...
6
votes
2answers
3k views

Why sponge can't absorb mercury

Recently I have watched a video demonstration with a sponge and mercury and the sponge can't absorb mercury like it does with water. Why is that?
12
votes
1answer
2k views

Why are the total energies of transition states so commonly corrected for zero-point vibrational energy?

So often I see total energies of transition states corrected for zero-point vibrational energy which always confuses me. Zero point energy is the lowest energy that a ground state minimum energy ...
1
vote
0answers
120 views

How effectively bound Na2CO3 and BaCL2 water

How fast does $\ce{BaCl2}$ bind water from its surroundings, becoming a hydrate, compared with same process with $\ce{Na2CO3}$?
10
votes
2answers
371 views

How can enzyme/substrate reactions that adhere (largely) to quantum theory also require 'Newtonian' consideration of gravity?

I'd just like to ask for a little clarification here due to confusion from interdisciplinary studies. I'm currently reading the 1976 paper related to the recent 2013 Nobel Prize for Chemistry, by 2 ...
1
vote
1answer
3k views

Heat Capacity and Calorimetry

Why does the heat capacity of a calorimeter, C(cal), need to be determined? A calorimeter contains 50.0 mL of water; both are at 21.2 degrees C. Then the 50.0 mL of water at 57.6 degrees C is added ...
1
vote
1answer
3k views

Do acids without hydrogen taste sour?

I have heard that acids taste sour because of hydrogen (I don't really know exactly). According to the definition of acids: An acid (from the Latin acidus/acēre meaning sour) is a chemical ...
3
votes
0answers
52 views

What Does the Equilibrium Constant represent? [duplicate]

If the Equilibrium constant stands for the extent of reaction at equilibrium, whether more of forward or backward reaction is taking place, then why is it not affected by factors like concentration of ...
0
votes
1answer
1k views

How do point defects in a crystal relate to Entropy?

I am interested in Non-Stoichiometry and how it relates to crystal structures; In particular I wish to learn about surfaces of metal oxides. I am aware that point defects in such crystals are a result ...
-4
votes
1answer
1k views

Strange observation!

Every one have observed that when we pour cool water into a transparent glass (or simply glass), some droplets accumulate on the outside part. Did the droplets come pass through the glass? If they ...
1
vote
1answer
4k views

Attempting to balance a redox reaction using half reactions leaves an unbalanced component

I have this redox reaction that I can't balance using half reaction method. $$\ce{Mg + HNO3 -> Mg(NO3)2 + N2O + H2O}$$ What I get at the end is $$\ce{2Mg + 6HNO3 -> 2Mg(NO3)2 + 3N2O +3H2O}$$...
4
votes
1answer
175 views

Solvated solids

I have a very basic question concerning solvation. If a solid (solute) was dissolved in a liquid (solvent), is the solute still in the solid state? or does it convert into another state of matter when ...
7
votes
1answer
2k views

How exactly is activation energy defined?

In a common interpretation of the Arrhenius rate equation $$k = A\exp\left(-\frac{E_\mathrm a}{RT}\right),$$ the activation energy $E_\mathrm a$ is understood to represent the difference in the ...
15
votes
2answers
4k views

Stoichiometric defects in silver bromide

Stoichiometric defects (Schottky and Frenkel defects) in ionic crystals are formed due to irregularities in the ionic arrangement which maintain the stoichiometry and electroneutrality of the solid. ...
1
vote
1answer
76 views

How to detect H₂SO₄ (aq) and NH₃

We have two bottle named $\ce{H2SO4~(aq)}$ and solution of $\ce{NH3}$ but we don't know their name actually. What I have to do to detect these solution by only using : $\ce{CuCl2}$ or $\...
7
votes
1answer
6k views

Is it possible to save an insoluble snowflake?

In The Big Bang Theory Season 3 Episode 1 "The Electric Can Opener Fluctuation" Leonard gives Penny a snowflake that will never melt. He said some type of chemical gas name when he try to explain, ...
4
votes
1answer
520 views

Why was anhydrous magnesium carbonate “upsalite” discovered so late?

What complicated the synthesis of upsalite (anhydrous $\ce{MgCO3}$), for it to be synthesized and published in 2013 as opposed to the 20th century, as one would expect for such a simple salt?