Questions tagged [ions]

For questions about ions - atomic or molecular particles having a net electric charge. Do NOT use this tag just because your question involves ions but is not about the ions themselves (as in electrochemistry, etc.).

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219 views

Conductivity measurements of demineralized water - Unexpected results. Looking for explanation

I'm trying to measure the conductivity change of demineralized water over a few days. But I get results I can't explain. Setup This is the circuit and cell I'm using: Where $R_x$ is the ...
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120 views

Thought Experiment: Is it possible to preserve the charge imbalance present during molten lead(II) bromide electrolysis?

Suppose I were to electrolyse some molten lead(II) bromide. According to what I have been taught, the lead ions travel towards the cathode and are reduced at it, while the bromide ions are oxidised at ...
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1answer
206 views

Why does the trimethylammonium cation have a larger -I effect than the ammonium cation?

Why does $\ce{N(CH_3)_3^+}$ have a larger $-I$ effect than $\ce{NH_3^+}$? Since the methyl group is good at donating electrons it would stabilize the charge on nitrogen atom, decreasing its ...
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69 views

What is the arrangement of water molecules in a hydration shell around an anion?

I believe I read somewhere that the hydration shell of ions always has hydrogen on the outside, but I can't relocate the exact whereabouts of this. Thus, I decided to ask here, as to what the ...
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78 views

Can this happen to superheated water?

Superheated water refers to water that is heating well beyond its usual boiling point under extreme pressure. This cause it to display anomalous property. I noticed that as temperature increases, so ...
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168 views

Why does viscosity decrease when divalent cations are dissolved into aqueous solutions of sodium carboxymethylcellulose?

Sodium Carboxymethylcellulose (CMC/NaCMC/Aqualon) is a common product used in many instances for its unique properties, especially its ability to make solutions viscous. It is well known that the ...
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175 views

Negative numbers for ionic radii?

I was looking for a good table of ionic radii for an experiment on the van't-hoff factor when I stumbled upon R. D. Shannon, Acta Cryst. 1976, A32, 751. In table 1, it lists 1 of the ions of carbon ...
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410 views

Why don't halogens form cations like H+?

The first ionization energy of hydrogen is $1312\;\mathrm{kJ\cdot mol}^{-1}$, which is larger than that of halogens such as chlorine, bromine, and iodine. Given that observation, why don't halogens ...
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229 views

Debye-Huckel theory with non-polar solvents

I want to calculate the activity coefficients of mixed solvent salt solutions. I am seeing very strange behavior when I try calculating the activity coefficient of salts in non-polar solvents using ...
4
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1answer
6k views

“Crystal radius” vs “Ionic radius”

What is the difference between crystal radius and ionic radius? For $\ce{NaCl}$ for example the ions combine to a crystal, and I would have guessed they are equal. But I then found an example of data, ...
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381 views

Do molecules like NH2 cation exist?

I saw that the book said that nitrogen cations must have four bonds and no lone pairs. I wasn't sure why you couldn't have a lone pair and 2 bonds.
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295 views

Enthalpy change of chromate-dichromate reaction

I am a uni study doing chemistry. I have taken a little bit in highschool before, but not in a while. In a (nonassessed) practical, we have to predict how heating a chromate/dichromate solution: $$\...
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355 views

Brewing tea with deionized water

I am wondering what efect brewing tea (let us assume for the sake of simplicity it is green tea, brewed at about 80 °C) in deionized water might have on the product. Will the lack of ions in the ...
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1answer
170 views

Positive charge on a zwitter ion at pH=7?

I faced this question. But I am having some problems understanding the solution to this: How can the negative charge on the peptide vanish on $\pu{pH = 7}$? Suppose, we have some $\ce{H+}$ donor on ...
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21 views

A question about nicotinamide adenine dinucleotide

In the structure of NAD+, why does the nitrogen of pyridine bind covalently to the the first carbon of glucose while the anion stabilizing the nicotine amide ion is the phosphate group? In other words,...
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55 views

Are dopant ions on a crystal lattice free or bonded?

This question seems simple but I don't seem to find many answers right away for this. When you make a crystal doped with ions (like a luminescent phosphor) and the ions then become a defect in the ...
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60 views

Bond dissociation energy of the trihydrogen cation

Recently, in one of the questions in an assignment on the topic of energetics, we were asked to explain why the bond dissociation energy for the trihydrogen cation is much larger than what we would ...
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33 views

QM modelling of charge separation reactions

I have a general question regarding the modelling of reactions in which neutral reactants form charged species/ions (in solution). How can one get the energetics approximately right on reactions like ...
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36 views

Ions not attached but included in chemical formula for tartrazine

In some diagrams for tartrazine ($\ce{C16H9N4Na3O9S2}$), I see that $\ce{SO3Na}$ is actually represented as $\ce{SO3^-}$ with a floating $\ce{Na^+}$ next to it. How does this work? EDIT: Wait, are ...
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3k views

Ionic radius of Al[3+] compared to K[+], Ca[2+], S[2-], and Cl[-]

I came across this question: Which of the following is bigger? $$\ce{K+, Ca^2+, Al^3+, S^2-, Cl-}$$ Now, I know that the radius decreases as the period progresses to the right and increases ...
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156 views

How will Back-Bonding affect molecular geometry?

While going through a textbook, I came across the following line: $\ce{R3C-}$ is pyramidal while $\ce{(CN)3C-}$ is planar due to lack of back bonding from the lone pair of carbon atom into the $\pi^...
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1k views

Mechanism Permitting Proton Sponge Effect

The proton sponge effect is utilized as a drug delivery method to release contents packaged in micelles (usually coated in PEG or another protective polymer) into the cytoplasm of a cell after being ...
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41 views

Ionic emission spectrum contamination

Imagine that I am trying to identify the presence of ions from among the metals $\ce {Li,Na,K,Ca,Sr, Ba}$ in some solution through their emission spectrum. By mistake the wire used to introduce ...
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218 views

Bond Energy of Ions of Molecular Oxygen

Three of the bond energies of $\ce{O2,\ O2^{-},\ O2^{2-},\ O2^+}$ have the values approximately $200, 490$ and $625\ \mathrm{kJ\ mol^{-1}}$. The value for one of the species is uncertain and, ...
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666 views

Dissociation of H3PO4 and colligative properties

Which of the following solutions that have concentrations of $0.01\ \mathrm{M}$ show the highest elevation in boiling point and why? A) $\ce{NaCl}$ B) $\ce{CaCl2}$ C) $\ce{H3PO4 }$ D) $\ce{...
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43 views

pH, conc vs activity

After studying a somewhat overview of "gamma" activity coefficient (it is not actually in our course but may come in exam as a part of unknown paragraph in ionic equilibrium) I can understand most ...
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324 views

Why is silver chromate red?

Copper(II) ions are blue and chromate(VI) ions are yellow therefore copper(II) chromate(VI) would turn out to be green because it's a mixture of blue and yellow. In the same way, silver ions are ...
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99 views

Calculating binding energies for excitated levels in potassium?

Suppose a laser is used to excite electronic transitions in potassium from the $3p$ orbitals to ones higher than $4s$. When I attempt to use the Bohr model to calculate binding energies, what I obtain ...
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72 views

Possible ionization and fragmentation of chemicals

Is there any generic method where I can know/calculate/generate the possible ionization and fragmentation of a specific chemical, for example, hydrogen chloride and water? This question is actually ...
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936 views

How to determine relative size of polyatomic ions?

How would you determine the size of a polyatomic ion? For example when determining which ion is bigger, $\ce{NH2-}$ or $\ce{I-}$, what would you use to determine the size difference? I know that $\...
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110 views

Why does the passivation layer in DRIE protect just the mask and not the substrate?

Here's a good link as an introduction to DRIE: BSAC: DRIE Process Development The $\ce{C4F8}$ (refer Pg. 9 on the link) passivates the entire top layer. But when $\ce{SF6}$ ion bombardment occurs, ...
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18 views

Lattice Energy of MX2 type

While finding the solution to the question that which among BaO and BaCl2 has hi that is energy I found that it was BaO whose lattice energy is high and there were explaining it just with charges. So ...
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25 views

Nature of the bonding in hexaaquaaluminium complex

$\ce {[Al(H2O)6]^3+}$ is a well-known complex ion formed by the $\ce {Al^3+}$. I have always had the understanding that only the aqua complexes of transition metal ions, such as $\ce {[Fe(H2O)6]^3+}$, ...
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54 views

Kinetic Shift of Simple Cleavage

What is the kinetic shift for the simple cleavage fragmentation if the ion source residence time is 100 microseconds, the time to reach the detector after leaving the ion source is 10 microseconds? (...
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38 views

how can I predict the rate of water ions precipitation on a surface?

Consider a titanium pot that contains 1kg water with the following ions: $[Ca^{2+}]=22000$ ppm, $[Mg^{2+}]=1500$ ppm,$[Sr^{2+}]=791$ ppm,$[Na^{1+}]=48000$ ppm,$[Cl^{1-}]=120000$ ppm,$[SO_4^{2-}]=...
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2answers
695 views

Why does beryllium lose two electrons when it’s orbitals are already full?

I have a rudimentary understanding of orbitals, as in what they are, the shapes (l, I think) and of the principles. So I was doing the electronic configuration for beryllium, it has 4 electrons. So ...
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76 views

How would you write the empirical formula of an ion?

How would you write the empirical formula of e.g. X2Y42-?
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144 views

Different values of concentration of product at equilibrium

$\pu{60g}$ of acetic acid and $\pu{46g}$ of ethyl alcohol are mixed with each other at a constant temperature and allowed to attain equilibrium. At equilibrium $\pu{58.2g}$ of ethylacetate and $\pu{...
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58 views

Which is a better measure of polarising power of a cation?

Recently, I have come across literature stating that polarising power of a cation is proportional to the inverse of the surface area $(4\pi r^{2})$ while some associate it with the charge density of ...
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23 views

Acid/base separation in nanofiltration

How do semi-permiable membranes handle salts that can separate into an acid and a base based on the "rules" of the membrane? For example, say I have a nanofiltration membrane that rejects ...
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0answers
131 views

Bond angles in a oxonium cation

What are the bond angles in protonated alcohol? The bonds in the carbon chain are presumably unaffected by the $\ce{-O^{+}H2}$ group and so in their usual tetrahedral arrangement; what are the angles $...
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194 views

Ionizing radiation and oxidation without oxidizing agents

My knowledge on this subject is a bit rusty, so excuse me if I'm asking the wrong question here. I was taking a look at my high school chemistry books from many years ago, and I noticed that reduction ...
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1k views

Ar atomic radius Vs. Mg2+, Al3+ and F-

I find it difficult to understand why the Atomic radius of $\ce{Ar}$ is lower than the ionic radius of $\ce{Mg^2+}$ and $\ce{F-}$, and higher than $\ce{Al^3+}$. According to the tables I've seen: $$\...
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522 views

Hydration enthalpy of cations

Can someone provide reliable data on the solvation / hydration enthalpies of $\ce{Ti^{4+}}$ and $\ce{Cr^{3+}}$ ions, or explain which is more stable qualitatively? According to this article1 CFSE in $...
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1k views

Distance between ions

I am doing a homework where I am supposed to calculate estimate od distance between two ions in cytoplasm. I have only been given the concentration of an ion. Any help how I should start looking this ...
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95 views

Why adding salt to kneading make it wetter?

Last week I tried a new recipe of pizza dough: 65mL of Water; 140g of Wheat Flour (typo 3); 7g of Yeast; 1 big spoon of Olive Oil; 25g of cooked potatoes; 1g of common salt; I think the recipe uses ...
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0answers
251 views

What are the factors affecting Boiling Point in Ions?

I understand that for molecular substances, intermolecular forces such as van der Waals forces and hydrogen bonding are the major factors effecting the boiling point. However, I am not sure about ...
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0answers
168 views

How do ion–dipole bonds manage to break apart an ionic lattice?

I was reading this answer and its reasoning behind the dissolution of NaCl seems to lie in entropic favorability. However, as it states, many, if not most, dissolution reactions are favored by ...
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0answers
285 views

Understanding three-dimensional structure of common salt

I started reading through The Feynman Lectures and came across this diagram. What do the numbers next to the nodes in the diagram represent? It's not explained in the text. All that is mentioned is: "...
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0answers
1k views

Why does sodium chloride not conduct as much as aluminum chloride in water?

I understand how $\ce{NaCl}$ and $\ce{AlCl3}$ dissolves in water but I'm wondering why one is more conductive than the other. Is it their extra ions to conduct the electricity? I know that in $\ce{...