Questions tagged [absorption]

In chemistry, absorption is a physical or chemical phenomenon or a process in which atoms, molecules or ions enter some bulk phase – gas, liquid or solid material.

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Calculating Band Gap Energy When Absorption Spectra Shifts with Concentration?

I am not a chemist. However, from some experimental work I have been doing, I have found that the intensity of the spectrum changes with dilution, this makes sense. However, when calculating the band ...
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7 votes
4 answers
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When pigments absorb light only around a single particular wavelength, why aren't they still white?

I'm trying to understand how organic molecules get their colour. One major factor are conjugated double bonds which create delocalized pi-orbitals (e.g. https://en.wikipedia.org/wiki/...
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Normalized absorbance/transmittance definition [closed]

In the absorption spectroscopy we can calculate transmittance $T$ of a given sample by comparing how the intensity of the incident beam $I_{0}$ is decreased with the distance (Lambert-Beer Law). $A = -...
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The reason for selection of wavelengths in the spectrophotometry of Quinoline Yellow SS

The absorption spectrum for Quinoline Yellow SS has peaks at 224 nm and 414 nm, and a trough at 337 nm. This experiment (see page 31), selects 224, 337 and 414 nm to be used in the spectrophotometric ...
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Solubility of nitrogen dioxide in sodium hydroxide

I know $\ce{NaOH}$ can absorb $\ce{NO2}$, but I could not find any data of solubility of $\ce{NO2}$ in $\ce{NaOH}$ at room temperature and atmospheric pressure. I am trying to figure out how much NaOH ...
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How rate of absorption remains same throughout the process?

While reading surface chemistry, I got Rate of adsorption is high at begining and then decreases till equilibrium is attained . On the other hand , rate of absorption remains same throughout the ...
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3 votes
1 answer
472 views

How to determine chlorophyll content from spectrophotometry data (absorbance vs wavelength)?

I boiled spinach solution (spinach leaves and 90% methanol) in solutions of varying $\mathrm{p}H$. I used a spectrophotometer to obtain wavelength ($\lambda$) vs absorption, and want to investigate ...
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1 answer
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Is there a type of fabric that absorbs smoke and odors, but also washes out? [closed]

I don't know where else to post this, and I also saw a question asking why fabric absorb odors so well so I'm hoping it fits here. Any explanation as to why one fabric over another would absorb odor ...
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Conditions for a substance to show deliquescent or efflorescent behaviour

I have learnt that deliquescent substances are the ones which absorb moisture from the surroundings and convert them to solution and efflorescent substances are the ones which release moisture into ...
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Can physical absorption happen despite the formation of products?

As far as I know, the absorption of $\text{SO}_2$ in water goes under physical absorption, meaning the sulfur dioxide bubbles are held in place by Van der Waals forces, in this case Keesom forces, ...
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Why is the IUPAC definition of adsorption so different from other definitions?

NB: This question has been edited. Originally, some of the confusion was caused by me not knowing that condensed phase could refer to solid phases as well. This has been removed, but the confusion ...
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Absorption spectrum of common plastic polymers

I am looking for data regarding absorption spectrum of common used plastic polymers, in the range of 200- 1.000 nm Moreover, I am looking for inorganic or organic compounds, which can be mixed ...
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Absorption Curves Normalization

I have absorption curves for three species that are nominally the same concentration that I need in order to calculate spectral overlap. Part of that process is dividing the curve through by the ...
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Adsorbable Organic Halides (AOXs) in bleach residue

I have a question regarding using household bleach, and wonder if someone knowledgeable can help, please? I have used household bleach (sodium hypochlorite, sodium hydroxide, coco alkyldimethyl, ...
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Why is there a mirror image effect in the absorbance and fluorescence spectra?

I've read some answers online but I still can't seem to understand the mirror image effect. Why is the highest energy absorption (v" = 0 to v' = 4) the lowest energy fluorescence (v' = 4 to v&...
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What type of spectroscopy can display several vibrational energy levels around the electronic transition?

My question is illustrated as the figure. As far as I know, due to the Franck-Condon principle, the absorption spectrum is related to the ground state to the excited state with the same geometry. Here ...
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How to think about absorption and emission rates and intensity for stimulated emission?

I learned Fermi's Golden Rule applied to absorption and stimulated emission and encountered the following question: Since absorption and emission rates are the same for stimulated emission, why can't ...
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The negative absorbance values in the baseline measurement

In the spectrophotometric analysis(uv-vis-NIR) of ITO Nanoparticles in tetrachloroethane using a double beam instrument baseline was measured with 2 identical cuvette with solvent only. This gives me ...
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“Good” properties of transparent conducting oxides

I'm a computer scientist and I'm trying to figure out which are the key properties that define a “good” acting transparent conducting oxide (TCO) in order to consider several possible features to ...
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4 votes
1 answer
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Absorption and emission at same wavelength?

Is it possible for a molecule to absorb and emit at the same wavelength? What is the reason behind it? I’m working on charged tin porphyrins and got the excitation and emission (fluorescence) ...
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1 vote
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Using the method of differential absorption to determine the ethanol content of an unknown sample [closed]

I have completed a whole set of FITR-ATR spectra analysing 6 solutions of ethanol-water mixtures, all at different concentrations of each. I have now been instructed to use the method of differential ...
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Solving for Concentration Using pseudo-First Order Kinetics

The following graphs represent a pseudo-first order bi-molecular reversible reaction with the formula $\ce{A + B <=> C}$: The reaction product has an extinction coefficient of $\pu{50000 M-1 cm-...
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Plasticisers and other impurities from polyethylene laboratory bottles?

Does polyethylene (PE), widely used for wash/squirt bottles in labs, contain soluble compounds such as plasticizers that can accumulate in organic solvents (e.g. alcohols, acetone) after prolonged ...
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Deriving the absorption coefficient from state transitions

This source states that the absorption coefficient $\gamma$ is proportional to the difference in particle number density $\Delta n$ per unit volume between the initial and the final rotational state ...
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Why do some molecules show non-symmetric absorption and emission bands?

I'm looking at a molecule of [Ru(bpy)3]2+ in water and the absorption and emission bands are not symmetrical. I want to know why the mirror image rule doesn't apply here. Is this because of the MLCT, ...
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absorption spectrum of hydrogen atom [closed]

In absorption spectrum of hydrogen atom, only one electron is present in its one atom which is in ground state, so it means that all electrons can only absorb energy of photon of wavelength which lies ...
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1 answer
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How to calculate the emission wavelength of a substance? [closed]

A light photon (700nm) gets absorbed by a substance*, this substance than emits the light photo. How to find out the wavelength emitted by this light photon? *substance can be anything, I've just ...
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When and how do mineral chelates separate in the body?

If one consumes an amino acid chelate such as iron bisglycinate, it is generally absorbed intact as far as I am aware. At some point, presumably the iron could be used for say hemoglobin synthesis and ...
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Maximum Value of Monolayer Capacity

What is the possible maximum value of the monolayer capacity? Is it possible for the monolayer capacity to exceed more than $(100)\frac{mol}{g}$ or even $(1000)\frac{mol}{g}$? Any help is highly ...
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1 answer
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Photoelectric effect with 0 Kinetic Energy?

Does the photoelectric effect take place if the frequency of the photon is exactly equal to the threshold frequency of the metal? I know the electron is going to be free, but it will have 0 kinetic ...
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1 vote
1 answer
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What is the difference between ideal stages and transfer units in a packed bed gas absorber?

I am having a hard time grasping what these two concepts are supposed to mean and how they differ. What I know so far is: In a counter-current gas absorber, if we set the inlet and outlet ...
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What is the effect of applied magnetic field on absorption spectrum?

Upon application of a weak magnetic field, a line in the microwave absorption spectrum of rigid rotor splits into $3$ lines. The quantum number $(J)$ of the rotational energy level from which the ...
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How to produce produce gel for ocean? [closed]

...
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2 votes
1 answer
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Are there chemicals that absorb and release upon heating oxygen more efficiently than potassium oxide? [closed]

$\ce{K2O}$ absorbs oxygen forming $\ce{K2O2},$ which decomposes to $\ce{K2O}$ and $\ce{O2}$ at 500 °C. This means that $\ce{K2O}$ can absorb up to 17% its mass of oxygen. Are there other substances ...
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1 answer
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Will charcoal briquettes (not activated) absorb water out of the air in the house in a subtropical climate?

I live in Florida, an incredibly wet environment where it's very difficult to get moisture out of house without using a dehumidifier 24/7, which is too expensive. Would charcoal briquettes be of any ...
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1 vote
0 answers
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How is Mn+7 in the Permanganate ion considered as momentarily reduced to +6 in LMCT? [duplicate]

I saw this passage on a book and it says that Ligand to Metal Charge Transfer (LMCT) overpowers d-d transitions thus the permanganate ion has an intense purple color. However, it was mentioned that ...
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Is the water absorbed by sodium polyacrylate available to react?

I'm curious whether the water absorbed by sodium polyacrylate would react with alkali metals, or be trapped by the sodium polyacrylate.
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2 votes
0 answers
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tolerable error, CASSCF simulation of UV/Vis spectrum

Please forgive my ignorance of experimental spectroscopy. I am a computational chemist, not an experimental one. My question is: what would be considered a tolerable or reasonable difference between ...
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3 votes
2 answers
10k views

When making a calibration curve, do we have to use the wavelength at maximum absorbance?

If you are making a calibration curve for $\ce{CuSO4}$ where you plot absorbance against concentration, does the wavelength have to be exactly at the maximum of the peak? Or can it be somewhere else ...
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5 votes
2 answers
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Vibronic coupling: How do I determine the new point group after vibration?

So I was recently discussing the transitions in Egyptian Blue ($\ce{CaCu[Si4O10]}$) with some of my students, who had to prepare this compound. What I like in particular in this case is how, at least ...
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0 votes
1 answer
354 views

What substance consumes oxygen from atmospheric air [closed]

I'd like to find an economical substance that will consume oxygen from a container. Steel wool comes to mind but I don't have an intuition how feasible it would be. The chamber is 5 gallons in size ...
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1 answer
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Effective attenuation coefficient for polychromatic light

The Beer-Lambert law gives the optical intensity of collimated light as a function of depth $z$ as: $$I(z)=I_{0}\mathrm e^{-\gamma z},$$ where $\gamma = \alpha + \beta$ is the wavelength-dependent ...
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Hygroscopic Substances and Drying Agents

My book says: Most of the hygroscopic substances are drying agents Based on what I read on several websites, I think dehydrating agents also act as drying agents. If so, all dehydrating agents ...
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0 votes
1 answer
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What kind of drugs can be absorbed through skin? [closed]

Some drugs such as nicotine can be administered through skin. I thought the layers of skin are designed to prevent in-flow of any chemical/germs. Not all drugs get absorbed in this fashion. So do ...
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1 vote
1 answer
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What is the relationship between emission and fluorescence?

A molecule exposed to a photon with some energy is put into an excited state, and emits a photon of some energy when it returns to ground state. The photon that provided the energy for excitation ...
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6 votes
1 answer
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What is the difference between dissolution and absorption?

Let us first look at the definitions from Gold Book: Absorption: The process of one material (absorbate) being retained by another (absorbent); this may be the physical solution of a gas, liquid, ...
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2 votes
1 answer
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Calculation of silver nanoparticle size using Mie Theory

I have synthesized silver nano-particles and I wish to determine the approximate particle size using the wavelength that was most absorbed according to its absorption spectrum. I find out that Mie ...
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3 votes
0 answers
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Explaining color differences using bond conjugation

I'd like to ask about how the color differences between the dyes methyl violet and malachite green can be explained. Looking at the conjugated bonds of each, methyl violet seems to be more conjugated ...
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10 votes
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Finding the wavelength of maximum absorption of Tartrazine using Fieser-Kuhn

How would you use Fieser-Kuhn rules to calculate the wavelength of maximum absorption for tartrazine? Fieser-Kuhn rules states that: $\lambda_{max}=114+5M+n(48-1.7n)-16.5\ R_{endo} - 10\ R_{exo}$ ...
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Determining the calcium content in cashews via titration?

I have been planning on an experiment for quite some time now (as part of my after-school chemistry club), but I still feel like I am missing something. Due to my family's calcium deficiency, I ...
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