Questions tagged [surface-chemistry]

Surface chemistry is roughly defined as the study of chemical reactions at interfaces between 2 or more phases.

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How can surface excess be negative?

If we have interphase of two phases $\alpha$ (water) and $\beta$ (air), surface excess is defined as $$\Gamma_i = \frac{n_{i,\mathrm{tot}} - n_{i,\alpha} - n_{i,\beta}} A = \frac{n_{i,\mathrm{int}}} A,...
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Modified Arrhenius equation in the presence of a heterogeneous catalyst

Suppose we are doing heterogeneous catalysis, for example, between nitrogen and hydrogen to create ammonia in the presence of a solid catalyst, like rhuthenium. It's obvious that the gas molecules don'...
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why Tin/Zinc alloys can be used to solder aluminum and Tin alone does not "wet" the aluminum?

It is impossible to solder aluminum with only tin, tin does not "wet" aluminum surface because of the instantaneous reaction aluminum/oxygen on the surface of the base metal (aluminum). I ...
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How can I prevent and remove oxidation on the surface of liquid Galinstan?

The oxide layer formed on galinstan (or its component of pure gallium) when exposed to air increases wetting and dulls the appearance. Is there a clear liquid material in which a blob of liquid ...
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Why does magnesium hydroxide solution solidify after passage of time?

I have been trying to make a suspension of magnesium hydroxide in water. Around 40% magnesium hydroxide w/w. Initially it is fluid, but as time passes, it solidifies. What is causing this?
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Contact Angle Hysteresis

When solid surface is wetted and dewetted with some liquid, contact angle measured will not be the same. I am not sure what does process of wetting or dewetting have to do with contact angle or why ...
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Owens - Wendt Model for Surface Energy of Solid - Liquid Interface

Owens - Wendt model is used for calculating surface energy on liquid - solid interface and it is given by following equation: $$ \gamma_{sl} = \gamma_s + \gamma_l -2(\sqrt {\gamma_l^d \gamma_s^d} + \...
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Preparing a surface with two different compounds in computational chemistry

I need to perform QM calculation on a surface built up by a junction of a Palladium surface with an cerium (IV) oxide one. I have the xyz file of both the surfaces, but the calculation should be ...
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LEED - determining surface structures

How can one describe surface structures (before and after adsorption)? I understand the diffraction theory but I have never really tried to determine the structures of samples by myself. LEED (low ...
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Adsorption on solids - homogeneous/heterogeneous surface definition

How could we define homogeneous and heterogeneous surfaces (rigorously)? It is among my exam questions (but I could not find any definition in my textbook or on the internet). I would say the ...
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Gold number and its specifications

$\pu{0.005 g}$ of a protective colloid is required to prevent precipitation of $\pu{1 ml}$ of gold sol on addition of $\pu{10 ml}$ of $10\,\%$ $\ce{NaCl}.$ The gold number is (A) $0.5$ (B) $5$ (C) $50$...
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Is this the first report that acetonitrile & propionitrile crystals create highly polar nano surfaces? How does one detect or quantify such surfaces?

Phys.org's Titan-in-a-glass experiments hint at mineral makeup of Saturn moon says: Titan, Saturn's largest moon, is a natural laboratory to study the origins of life. Like Earth, Titan has a dense ...
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What is the liquid of syneresis

When gels are allowed to stand for a long time, they give out some quantity of liquid, which is present on surface of gel.This is syneresis. What is this liquid? Is it the same colloid which formed ...
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Why is there preferential adsorption of a common ion during preparation of colloids by peptization?

There was a similar question asked here on Chem SE, but the answer was not very satisfactory to me, so I am asking a fresh question. Peptization is the process of creating a colloid from a precipitate ...
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What is the theoretical reason for the dependence of the surface tension on the alcohol concentration in water?

The qualitative sketches I, II and III given below show the variation of surface tension with molar concentration of three different aqueous solutions of$ \ce{ KCl, CH_3 (OH) }$and $ \ce{CH3(CH2)_{11} ...
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Why does physisorption pass into chemisorption on increasing temperature

I have been told, that on increasing temperature, physisorption passes into chemisorption (with greater Activation Energy, generally). But why does that happen? Shouldn’t the increment in Temperature ...
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A liquid which climbs out of its pot [closed]

My Russian born wife recently asked me to buy her a skin remedy widely used in Russia. In English this is the oil of a plant called Sea Buckthorn. It is a thin yellow liquid. My wife put some of this ...
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Can suspended solid particulate particles adsorb on surface?

Gaseous and liquid particles adsorb on solid surfaces. Can solid particles suspended in a fluid medium also adsorb on these surfaces in the same manner?
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If something is not hydrophilic, is it necessarily hydrophobic?

Is it possible to create hydrophobic water? Two species are phobic within some medium under some conditions when they don't here together (cohere if they're the same species; adhere otherwise). To be ...
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Do lyophilic sols have an electrical double layer?

"There are two factors which are responsible for the stability of lyophilic sols. These factors are the charge and solvation of the colloidal particles". Quoted from NCERT book of OC But we ...
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Why is Freundlich adsorption isotherm not valid at high pressures? [duplicate]

I have taken the following from Wikipedia : Limitation of Freundlich adsorption isotherm : Experimentally it was determined that extent of gas adsorption varies directly with pressure, and then it ...
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Are oxides of sulphur and carbon adsorbed into limestone/marble?

Oxides of sulphur and carbon are commonly present in the atmostphere in areas close to industries, can such oxides get adsorbed into the surface of limestone and marble and cause discolouration and ...
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How can the difference between surface energy and electrostatic repulsion be calculated in electroplating?

When metals are electroplated unto surfaces, there are a myriad of forces at play. To set a clear example, if one were to electroplate a magnet with a diamagnetic metal such as bismuth, there will be ...
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Practical to measure topography of a large area (mm-scale) with scanning probe microscopy (SPM)?

I'm currently very new to nanotechnology. I do understand that it is possible to achieve an excellent topography image of a sample by SPM. However, is it possible to do SPM over a large area (for ...
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How lyophilic colloids reduce surface tension?

Its given in my textbook that surface tension of lyophilic/hydrophilic solution is lower than water. But my intuition says,since in lyophilic solution the interaction between a lyophilic colloid and ...
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How thick is the colored oxide layer on heat treated stainless steel? [closed]

When stainless steel is welded, or just heat treated, it will develop a thicker oxide layer, which in some cases is is rainbow colored, but can become so thick as to appear almost black. From the ...
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Viscosity at CMC

What happens to viscosity at critical micelle concentration? Does it increase or decrease abruptly, and if so, what's the reason behind it? I'm aware of changes in other properties such as ...
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Relationship between surface energy of liquid and solid states

I have been experimenting with different kinds of hot-melt (hot glue) adhesives. I have been comparing EVA to acrylic on various substrates. In comparing the two I have found the acrylic to be ...
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Sticking coefficents for dissociative adsorption

I am trying to simulate the decomposition of Hydrogen Peroxide ($\ce{H2O2}$) on $\ce{Pt}$ using Chemkin Pro. I am using a two step global reaction model for the reaction which is as follows- $$\ce{...
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Why does rate of chemisorption decrease with increase in pressure?

My textbook says that rate of chemisorption decrease with increase in pressure. I do found a similar statement on the web but couldn't understand this. The rate of chemisorption depends on the flux ...
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How does soap actually reduce surface tension of water

I was a bit confused on how soap reduce surface tension of water.I've read some answers like Why does soap reduce surface tension of water and Why do surfactants lower the surface tension But the ...
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How stable are surfaces functionalized with APTES?

I'm wondering specifically about magnetite micro particles functionalized/silanated with (3-aminopropyl)triethoxysaline (APTES), though I assume the stability would be the same for most surfaces. By ...
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How is ECR (Electron Counting Rule) done in a structure?

I've been told how to apply the ECR to GaAs{001}(2×4) in my lectures but it makes no sense to me and I don't seem to be able to find any other sources that explain this. (This is a further question on ...
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Could someone advise me on sources for crystallography and surface sciences?

I'm a physicist learning crystallography and surface science on the side of my research and I came across the concepts: surface reconstruction in hexagonal materials, unit mesh of surfaces, etc. I was ...
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Change in surface tension of soapy water as oil is added

I am wondering about how the surface tension of clean soapy water changes as oil is added to it? Is the change gradual or is it abrupt as the amount of oil added exceeds the amount of soap available ...
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Problem with epoxy silane (Random results in glass silanization). What are crucial points to look at?

I`m trying to immobilize an antibody onto the glass surface by means of GPTOMS (glycidoxypropyl trimetoxy silane). Using the same protocol (silanization in toluene) I get different results any time, ...
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What is the influence of citrate on PEG-modified polyacrylamide hydrogels?

I've been having a puzzle explaining the experimental results with the citrate anions and PEG modified polyacrylamide: According to the experimental data there is a hydrogel swelling whenever citrate ...
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surface energy versus surface tension and contact angles

I am hoping to measure the surface tension between two fluids (salt water and isopropyl alcohol), by measuring the appropriate contact angles, and applying Young's equation: https://en.wikipedia.org/...
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1answer
213 views

Finding the Freundlich adsorption isotherm from the graph of log(x/m) v/s log(p)

The following problem was asked in JEE Mains 2020 (Sept 2, Shift 1), The mass of gas adsorbed, $x$, per unit mass of adsorbate, $m$, was measured at various pressures, $p$. A graph between $\log\frac ...
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Thermodynamics of micellisation

Micellisation is found to be spontaneous i.e. $\Delta G < 0.$ It's found that $\Delta S > 0,$ which was intuitive since, solvated molecules are released. And, it may be most loosely started that ...
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Am I getting the details of mechanism of adsorption right?

Particles on the surface of a substance have a net force towards the geometric center of the substance called residual force. When molecules come close enough to the surface of a substance the ...
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Correlation between redox pseudocapacitance, surface area, and cell potential with metal oxide electrodes

I'm having difficulty intuitively reconciling two different ideas concerning metal oxide thin films in contact with aqueous solutions: 1) that charge storage by both redox pseudocapacitance and ...
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Why is a drop of chloroform stretched/pulled apart on a water surface?

I distributed drops of chloroform (with a lipid in them) on water (in a Langmuir-Blodgett trough). The chloroform drops form a layer on the water (so that the lipids are distributed on the water ...
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Effect of solutes on surface tension

What happens to the surface tension of a solvent, say, water when we mix a solute in it? For the sake of concrete discussion, the examples that I encountered in a test were sodium chloride $(\ce{NaCl})...
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The dissociation of hydrogen on UO2 and PuO2 surfaces: Homolytic or heterolytic?

I have seen that $\ce{H2}$ can dissociate on a metal-oxide surface by two methods: Heterolytically, forming a proton-$\ce{O}$ bond ($\ce{OH}$ group) and a hydride-metal bond ($\ce{M-H}$) on a metal-...
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Chemicals to increase surface tension of water

I want to increase the surface tension of water by 1.2 - 2 times. How about adding one or more chemical substances to the water that can possibily increase its surface tension by the desired amount? ...
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Why does silver stick to the glass in Tollens' test? [duplicate]

Why does it not simply form a solid powder at the bottom of the flask? Does silver also stick to the glass in other silver precipitating reactions? EDIT: My question is definitely not the same as ...
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Why are van der Waals' forces between gas molecules strong near its critical temperature?

My textbook says …easily liquefiable gases i.e. with higher critical temperatures are readily adsorbed as van der Waals' forces are stronger near the critical temperatures. What I do understand is ...
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Can Ferrofluids vaporise to gaseous state and Condense back to liquid state and do it many times over? [closed]

Here is the Link for Ferrofluids for basic idea. After going through this Wiki link, probably many people will come to a conclusion like when Ferrofluid boils, its carrier liquid vaporises and nano ...
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Temperature Programmed Disorption

For second part of the question I'm wondering if the peaks on the right denote the chemisorbed layer, while the peaks on the left denote the physisorbed layers. Since chemisorption results in a ...

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