# Tag Info

20

Good catch - you are absolutely correct. This is a mistake in the Wikipedia page, as a quick check with the reference listed there confirms. The values are the wrong way around. Changing it now... Edited to add: this of course raises the question of why it should be this way around. A somewhat hand-wavy answer is that, just like in benzene, the $p_z$ ...

14

Electric charge is transferred by physically moving charged particles around. In the case of an electric current moving through a wire (for example), the electrons are moving. In an ionic compound, the ions are locked in place. They can move around a little bit, but there is not much translational motion - the ions stay in their places on the crystal ...

13

This can arise due to ion-ion interactions brought on by Coulombic fields. A proper explanation is rooted in transport phenomena. Unfortunately chemists are largely not taught this, but chemical engineers do get the opportunity. Under standard conditions, ions in a solution will take a random walk during diffusion. This results in no net movement of our ...

10

The trick with graphene is that a lot of its amazing properties only work when you have continuous perfect sheets of it, and making graphene like this is currently beyond us, for large scales anyways. It is true that graphene has very high electron mobility $\approx10^{5}~\mathrm{cm^2/Vs}$ at room temperature, which works out to on the order of $10~\mathrm{n\... 9 Look at the II-VI options from a chemical perspective. For silicon, Group III boron p-doping would be replaced by Group II beryllium doping, and Group V phosphorus n-doping would be replaced by Group VI sulfur doping. The beryllium would tend to act like a Lewis base that donates a pair of electrons to some nearby silicon atom, forming a stronger and more ... 9 The answer to this question hinges on two key questions: What kind of dust are we dealing with? How is the dust arranged (i.e. what is your experimental setup)? Which Dust? Firstly, I'm going to assume you meant domestic dust (since there are more kinds of dust than you'd imagine). I quote Wikipedia: Dust in homes, offices, and other human ... 9 At low concentration, conductivity is proportional to concentration (a linear relationship). Each ion will have its own unique mobility, as discovered by Kohlrausch.$\ce{H+}$has the highest mobility. As you can see in your graph the acids have higher conductivities than the salts.$\ce{OH-}$is also highly mobile. As concentration increases, the linear ... 8 2-Methylpropane has a$\mathrm{p}K_\mathrm{a}$of 53 ($\mathrm{p}K_\mathrm{a}$table). That sounds pretty non-ionic. Can't think of any common all-carbon (no substituents of any kind) liquid compounds. 8 Delocalized$\pi$orbitals do allow for mobile charges. The catch there is "allow." Just because these systems can have mobile charges does not make them conductive. Conductivity can be defined as:$\sigma = n e \mu$where$e$is the charge on an electron,$\mu$is the charge mobility, and$n$is the number of charges. In the case of$doped$conjugated ... 8 ringo makes good points in his answer. Additionally, though, the increased temperature enhances mass transfer of ions to/from the electrode surfaces by at least two mechanisms: Higher temperature results in lower electrolyte viscosity, leading to a thinner fluid dynamic boundary layer and concomitant greater mass transfer to/from the electrode surfaces. ... 8 You can't conclude that by thinking alone; some experiments are necessary. True, an electron in an electride is kinda "free", in that it isn't connected to any particular atom. But that doesn't mean it can roam the entire structure, free as the wind. In fact, it sits in a potential well formed by the neighboring ions and molecules, only the well is so wide ... 7 Molar conductivity is defined as the conductivity of an electrolyte solution divided by the molar concentration of the electrolyte, and so measures the efficiency with which a given electrolyte conducts electricity in solution. It's unit in S.I. is: $$\ce{S.m^2.mol^{-1}}$$ 7 This is, ultimately, a question on solid state physics rather than chemistry. Further, the OP indicates that they are in high school, which kind of limits the depth of the answer that might be useful to them. However, I will try to make a simple, yet detailed answer. As atoms are brought closer and closer together, their electron clouds overlap and interact.... 7 To reiterate Ivan's comment fullerene is a bad conductor because that's what the measured properties produce as a result. The mechanism that makes it a bad conductor is that it has shorter range continuity than graphite. In graphite the carbon is made of sheets that can be as long as the sample. These sheets have fairly low conductivity, but when the ... 7 The reasoning here is two-fold. The solubility of most electrolytes increases with temperature, and water's ionization constant also increases with temperature. On the whole this means more ions, and thereby better conductivity. 6 Interestingley enough, there are papers entirely devoted to the subject of measuring the properties of living skin. The paper linked gives a value of$7 \times 10^{-4}~\mathrm{\frac{cal}{cm\, s\, °C}}$for human skin, or in everyday units used nowadays:$0.29 ~\mathrm{\frac{W}{m\, K}}$. This is only for the dermis, the part of skin that then gets transformed ... 6 One of the reasons why non reactive metals are good conductors is that they are good at staying as metals. Most metals react with the atmosphere to form oxides. And the majority of oxides are insulators or semiconductors. Of course there are few exceptions to this rule. Also, just a note: calcium and iron have better conductivities than platinum. 6 It depends on what you are prepared to consider a gas and what you are prepared to consider room conditions. The gas inside all discharge lamps (fluorescent lamps and neon lamps in shop signs, for example) conducts electricity and the lamps work under normal room conditions. However, the gases are often at low pressure and are, strictly speaking, plasmas ... 6 Air at STP does conduct a tiny bit due to ionization by cosmic rays; this might even provide a path for lightning leaders. "Alex V. Gurevich of the Lebedev Physical Institute [et al] suggest that... cosmic ray... might provide a conductive path that initiates lightning." In addition, ionization-type smoke detectors use a little radioactive material (e.g.$\...

6

When a current is passed through an electrolyte, a chemical reaction takes place. This alters the composition of the solution over time and you won't actually be measuring the conductivity(or conductance) of the initial solution. Since in AC current, equal current flows in both directions over a given amount of time(larger enough than time period), reaction ...

6

Decrease in temperature has two effects, both attributing to lower electrolytic conductivity: decreases the mobility of the charge carriers (e.g. $\ce{H3O+}$ and $\ce{OH-}$ for pure water); suppresses auto-ionization of water (higher $\mathrm{p}K_\mathrm{w}$), reducing the total number of charge carriers.

6

According to the Stokes-Einstein-Debye theory, and assuming the ionic composition remains constant (say for a fully dissociated salt), the main factor accounting for the response of the conductivity to temperature is the change in the viscosity of the solvent. In the SED theory the frictional drag coefficient $f$ of a charged particle is proportional to ...

5

Ron's answer is a good option, however autoionization is not necessarily equivalent to self-protonation. There may be some solvents where autoionization is even more suppressed than any self-protonation reaction. Perhaps the liquid with the lowest tendency to ionize may be something composed of molecules with extremely strong bonds, for example liquid ...

5

Look in the Wikipedia article Ion transport number. Lower case lambda, $\lambda$, is the molar ionic conductivity Upper case lambda, $\Lambda$, is the molar conductivity. $\lambda = t \dfrac{\Lambda}{\nu}$ Where $\nu$ is the number of ions for the cation or anion in the molecule. So $\ce{Na3PO4}$ would have 3 cations per molecule, but only 1 anion per ...

5

I can understand your frustration. The use of terminology is often inconsistent and confused (much to my chagrin). I think you've got the general idea, the conductance (G) can be defined as follows: $$G = \frac{1}{R}$$ i.e the ease with which a current can flow. As you said said, $$R = \rho \frac{l}{A}$$ one can now identify, $$G = \kappa\frac{A}{l}$$ ...

5

TL;DR: The addition of boric acid effectively switches the conducting anionic solute from hydroxide to borate, which has a lesser contribution to the conductivity due to its larger size and corresponding lower diffusivity. Most solute systems will not behave this way. In sufficiently dilute solution, the contribution $\kappa_i$ of each dissolved ion to the ...

5

I agree with the commenters that electrical conduction is very unlikely, but it's worth going through some possible mechanisms: actual solvated electrons: As others have noted, free electrons would be expected to react rapidly with protons, even in a basic solution, so this changes quickly to a scenario of sequential electron transfer between protons, so ...

4

In fact there are many factors to consider, so the answer to your question depends on what type of material you are analyzing. First of all you should know that even if the absorption level are discrete the absorption and the emission of a material are never a single value but a peak. If you consider the absorption or the emission of a gas you can assume ...

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