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According to wikipedia, shielding effect only happen in atoms which have more than 1 electron shells. The core electrons repel the electron on valence shell. But I heard some lectures mentioned the shielding effect on helium atom when they explained why the first ionization energy of He is not exactly 2 times more than... |
According to Graham's Law, the effusion rate of a gas is inversely proportional to the square root of the molar mass of the gas. However, consider this situation:
We have 1 balloon with 1 mole of neon gas and another with 2 moles of neon gas. The gases are in thermal equilibrium and occupy the same volume. In this s... |
How does the number of moles of gas affect the rate of effusion? |
According to Wikipedia, the shielding effect only happen in atoms which have more than 1 electron shells. The core electrons repel the electron in the valence shell. However, I have heard some lectures mention the shielding effect on helium atom when they explained why the first ionization energy of $\ce{He}$ is not ex... |
Why does helium seem to exhibit an ionization energy affected by the shielding of electrons? |
The question is: If $2.0 \cdot 10^{-4}$ moles of dye in $50$ mL of solution is consumed in 188 seconds, what is the average rate of consumption of dye in $\text{mol}/\text{L}\cdot \text{s}$?
I am not sure if I have done this correctly. I use the rate of reaction formula which is $\text{Rate} = -\frac{d[A]}{dt}$ Ther... |
Is the scientific explaination behind Smartkleen legit? |
I'm trying to have a conversation/debate about the SmartKleen laundry detergent alternative, but lack the knowledge to understand if their [explanation][1] is science or pseudoscience.
Far Infrared emission at cold water temp, smaller water molecule clusters, magnets that increase levels of dissolved oxygen, etc., c... |
Is the scientific explanation behind Smartkleen legit? |
The question is: Suppose we found that the reaction of Red#3 with bleach is 1st order in hypochlorite. The observed rate constant (kobs) for one of the trials was measured to be 0.00400 s^-1. If the concentration of hypochlorite was fixed at 0.134M, calculate the specific rate constant (k) for that trial.
I am very ... |
For a methlybenzene (with the methyl group at position 1), is it easier for chlorine to substitute the hydrogen at position 2, 3 or 4?
I was thinking somewhere along the lines of different charge densities around the benzene ring, and that the charge density closest to the already existing methyl group has been dimi... |
For methlybenzene (with the methyl group at position 1), is it easier for chlorine to substitute the hydrogen at position 2, 3 or 4?
I was thinking somewhere along the lines of different charge densities around the benzene ring, and that the charge density closest to the already existing methyl group has been dimini... |
For methylbenzene (with the methyl group at position 1), is it easier for chlorine to substitute the hydrogen at position 2, 3 or 4?
I was thinking somewhere along the lines of different charge densities around the benzene ring, and that the charge density closest to the already existing methyl group has been dimini... |
HEPES, the buffer, has the chemical formula C<sub>8</sub>H<sub>18</sub>N<sub>2</sub>O<sub>4</sub>S.
Using the Ionic Strength formula from Wikipedia (http://en.wikipedia.org/wiki/Ionic_strength).
I have calculated that 0.1M of HEPES would have a strength of 1.7M, would it be possible to confirm whether this is co... |
Ionic Strength of 0.1M of HEPES? |
For example, if I were to draw the structure of 1,2,4-trimethylcyclohexane, then would one or both of these be wrong?
![enter image description here][1]
[1]: https://i.stack.imgur.com/L4ndc.png
Or are both right? I'm wondering if it matters where I start to count from 1 in these cases, if there is some con... |
Does it matter which end of a chain one sets to be 1 when drawing the structure of organic compounds? |
HEPES, the buffer, has the chemical formula $\ce{C8H18N2O4S}$.
Using the [Ionic Strength formula from Wikipedia][1].
I have calculated that $0.1M$ of HEPES would have a strength of $1.7M$, would it be possible to confirm whether this is correct or not? (I have little chemistry knowledge).
[1]: http://en.w... |
I think the idea of "smaller water clusters" penetrating the cloth more efficiently is actually quite smart as the same idea is utilised in steam cleaners. But the rest of the article is a bit too psychotic. How can they say that colours are preserved while the Ball constantly generates H$_2$O$_2$ (in every second)? An... |
How can tin nitrate be synthesized? Mixing nitric acid and tin makes tin oxide (I did this in chemistry class) so how can tin nitrate be created? |
Make tin nitrate? |
A quick look into some search engine results for tin nitrate yielded [this source](http://www.nhehs.org.uk/chemistry/_Lead%28II%29_nitrate_Tin.html), which rather interestingly even comes with a video of the reaction. That probably isn't among the main routes to generate tin nitrate, though.
It seems the direct rea... |
In my organic chemistry lab (next week, the experiment has not been conducted yet) we are being asked to react anisole with bromine to get 2-bromoanisole (as well as 2,4-dibromoanisole and all the others). In our lab instructions we are told to add anisole, bromine and glacial acetic acid to our mixture. No mention o... |
Why use glacial acetic acid in bromination of anisole? |
>[...] bromine is not reactive enough to brominate an aromatic without FeBr3
That's true for benzene, but the methoxy-group in anisole isn't just *o/p*-directing.
**It is activating as too**. Actually, it's that much activating that anisole will react with bromine even without the presence of a Lewis acid.
So, ... |
>[...] bromine is not reactive enough to brominate an aromatic without FeBr3
That's true for benzene, but the methoxy-group in anisole isn't just *o/p*-directing.
**It is activating as too**. Actually, it's that much activating that anisole will react with bromine even without the presence of a Lewis acid.
So, ... |
>[...] bromine is not reactive enough to brominate an aromatic without FeBr3
That's true for benzene, but the methoxy-group in anisole isn't just *o/p*-directing.
**It is activating as too**. Actually, it's that much activating that anisole will react with bromine even without the presence of a Lewis acid.
So, ... |
>[...] bromine is not reactive enough to brominate an aromatic without FeBr3
That's true for benzene, but the methoxy-group in anisole isn't just *o/p*-directing.
**It is activating as too**. Actually, it's that much activating that anisole will react with bromine even without the presence of a Lewis acid.
So, ... |
I am looking to calculate the minimum heat needed to create vapor from a specific mixture. I have a mixture of 60% C3H803 and 40% C3H802. Total volume of the mixture is 3ml. Here are some facts that I know
C3H802
Density = 1.04 g/cm³
Boiling point = 370.8 F (188.2 C)
Molar mass = 76.09 g/mol
... |
As we know that $KOH$ absorbs $CO_2$, then why can't it be used to remove the excessive $CO_2$ present in the atmosphere? |
Why can $KOH$ not be used to remove atmospheric $CO_2$? |
As we know that $\ce{KOH}$ absorbs $\ce{CO2}$, then why can't it be used to remove the excessive $\ce{CO_2}$ present in the atmosphere? |
Why can potassium hydroxide not be used to remove atmospheric carbon dioxide? |
I am looking to calculate the minimum heat needed to create vapor from a specific mixture. I have a mixture of 60% $\ce{C3H8O3}$ (glycerine) and 40% $\ce{C3H8O2} $ (propylene glycol, propane-1,2-diol). Total volume of the mixture is 3ml. Here are some facts that I know
C3H802
Density = 1.04 g/cm³
Boili... |
When I look up the definition of ionization energy, it says it is the energy to remove one electron from the shell to infinity in the gaseous state. Why is it measured in gaseous phase but not other? |
Why the ionization energy is measured in gaseous phase? |
It seems relate to the atomic size but hydrogen also gets a smaller atomic size than fluorine. Why fluorine is the most electronegative atom? |
Why fluorine is the most electronegative atom? |
When I looked up the definition of ionization energy, it says:-
> it is the energy required to remove one electron from the shell to
> infinity in an atom in gaseous state.
Why is it measured in gaseous phase and not in any other phase? |
Why is ionization energy measured in gaseous phase? |
It seems related to the atomic size but hydrogen has a smaller atomic size than fluorine. Why is fluorine the most electronegative atom? |
Why is fluorine the most electronegative atom? |
The question is:
> Suppose we found that the reaction of Red#3 with bleach is 1st order
> in hypochlorite. The observed rate constant ($k_{obs}$) for one of the
> trials was measured to be $0.00400 s^{-1}$. If the concentration of
> hypochlorite was fixed at $0.134M$, calculate the specific rate constant
> ($k$... |
I'm kinda new to Chemistry, I know this is a very basic question.
How many moles of the substance are in the following amounts?
a) 2.50 g of lead
What I did:
Atomic mass of Pb: 207.2 amu or g?
1 mol of Pb -> 207.2 g
x -> 2.5 g
x = 2.5/207.2= 0.0121 mol of Pb
Should... |
Vapor is efficiently evolved when the sum of the vapor pressures is one atmosphere (boiling) given each mole fraction in homogeneous solution, rimmed by non-idealities. You then must input the latent enthalpies of vaporization to move mass.
That is the juice for a vapor inhaler. The sum of the enthalpies of heatin... |
I'm reading a high school chemistry course online, and I'm now reading about geometric isomers.
They provide this example:
![enter image description here][1]
And in terms of naming it, they say this:
>Begin by identifying the parent chain - it is the continuous chain that contains the carbon-carbon double ... |
Why is this organic compound trans, and not cis? |
The inert pair effect describes the preference of late $p$-block elements (elements of the 3rd to 6th main group, starting from the 4th period but getting really important for elements from the 6th period onward) to form ions whose oxidation state is 2 less than the group valency.
So much for the phenomenological pa... |
So looking at the Wikipedia pages of [Sulfur Tetrafluoride][1] and [Silicon Tetrafluoride][2], the melting points are -121 degrees C and -90 degrees C respectively, and so SiF4 has the higher melting point. However, their boiling points are -38 degrees C and -86 degrees C, respectively, giving SF4 the higher boiling po... |
What is the (conceptual) difference between binding energy and adsorption energy? |
Take a glass rod and rub vigorously the wall of the flask, the substance will crystallize out of the solution.
Take a fire polished stirring rod and etch (scratch) the glass of your beaker. The small pieces of glass that are etched off of the beaker serve as nuclei for crystal formation
But reaching back to my ... |
So looking at the Wikipedia pages of [sulfur tetrafluoride][1] and [silicon tetrafluoride][2], the melting points are -121 degrees C and -90 degrees C respectively, and so $\ce{SiF4}$ has the higher melting point. However, their boiling points are -38 degrees C and -86 degrees C, respectively, giving $\ce{SF4}$ the hig... |
Why does SiF4 have a higher melting point than SF4? |
So looking at the Wikipedia pages of [sulfur tetrafluoride][1] and [silicon tetrafluoride][2], the melting points are -121 °C and -90 °C respectively, and so $\ce{SiF4}$ has the higher melting point. However, their boiling points are -38 °C and -86 °C, respectively, giving $\ce{SF4}$ the higher boiling point.
I can... |
Why does SiF4 have a higher melting point than SF4? |
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 electrons.
**How did we derive this equation?**
I know the orbital angular momentum of electron is given by $\sq... |
I am dealing with the dissociation of water into its components hydrogen and oxygen and I am trying to determine the standard Gibbs free energies of each component. My professor said if the substance is an ideal gas in the standard state then
$$g_{i}^{0}=g_{i}^{\text{pure IG}}(T, P_\text{ref})$$
Now this means I ... |
Reading this article on Wikipedia: [Xenon Medical applications][1] I see that Xenon can be used as an anesthetic, neuroprotectant and doping agent.
If it is a noble gas, and thus, chemically stable, how can it have those properties?
If Xeon does not react with any other chemical, how does this happen, from a chem... |
>If Xeon does not react with any other chemical, how does this happen, from a chemical point of view?
- If molecules of phospholipids do not react with each other, how do they form biomembranes?
- If Xenon doesn't react, how can it form [host-guest complexes with cryptophanes][1]?
**It's not necessary to for... |
On Wikipedia, it says that polyethylene terephthalate (PET) decomposes at temperatures above 350°C.
What are these decomposition products? I read further that acetaldehyde is produced, but is that the only decomposition product?
Also, what compounds are produced when PET is burned? ($\ce{+O2->?}$) |
I was re-sorting books the other day, and thought about how many years it has been since I bought my Merck Index. I'm sure there are new entries in the more recent additions, but I do not have such a need to stay that up-to-date.
At first thought, it seemed to me that a book of this nature only adds entries, and doe... |
Are entries ever removed from the Merck Index? |
The Ionic Strength is calculated as:
$$I=\dfrac{1}{2}\cdot\sum{c_iz_i^2},$$ where where $c_i$ is the molar concentration of ion i ($M,\,mol/L$), $z_i$ is the charge number of that ion, and the sum is taken over all ions in the solution.
This is your HEPES molecule ($C_8H_{18}N_2O_4S$):
![enter image descriptio... |
I know that catalysts don't undergo chemical changes during a reaction, but do they undergo physical changes? If they do, are there any examples? |
Do Catalysts Undergo Physical Changes During a Reaction? |
>I know that catalysts don't undergo chemical changes during a reaction [...]
They don't? How then, other by forming a complex with the starting material, is the activation energy of that reaction lowered?
I do however agree that - in the ideal case - this step is reversible and leaves the catalyst unchanged afte... |
Surprisingly, there are very few resources online (outside of obscure lab pages) that explain exactly what standardization is (not even Wikipedia!). The context is the phrase _standardize the titrant_ for a titration. Does this mean you titrate it with a known solution? |
What's Standardization, and why do it? |
> Standardization is doing a titration to work out the exact
> concentration of _the solution you want to use_ to determine the
> concentration of an unknown solution.
Where _the solution you want to use_ is the titrant
See : http://answers.yahoo.com/question/index?qid=20090903183139AAXfQGm
|
Reading this article on Wikipedia: [Xenon Medical applications][1] I see that Xenon can be used as an anesthetic, neuroprotectant and doping agent.
If it is a noble gas, and thus, chemically stable, how can it have those properties?
If Xenon does not react with any other substance, how does this happen, from a ch... |
I tried writing an analogy to explain the difference between enantiomers and diastereomers. However, I'm not entirely sure if it's actually a correct representation of the differences. It might also be more confusing than it has to be:
>To use an everyday object as an illustration of the difference, imagine two fork... |
Is this analogy explaining the difference between enantiomers and diastereomers correct? |
Why are superoxide ions stable only in presence of large cations such as $\ce{K}$, $\ce{Rb}$ and $\ce{Cs}$? |
How do I overlay spectra in an ACD/NMR Processor, version 12.01? |
The smell is often noticed at construction sites, when reinforcing bars are welded or cut. Constructional steel contains about 0.1% carbon and phosphorus.
Phosphorus normally isn't welcome since it renders steels more brittle. On the other hand, it increases the corrosion stability. This is is a desired property for... |
I am wondering what chemicals exactly form the smell of a septic tank system. I read about H2SO4, NH3, but I am not sure. Is methane also a factor or is that odorless? |
what chemicals cause the smell of a septic tank? |
I am wondering what chemicals exactly form the smell of a septic tank system. I read about $\ce{H2SO4}$, $\ce{NH3}$, but I am not sure. Is methane also a factor or is that odorless? |
I am attempting to generate the probability for the specific speed of a molecule using the [Maxwell-Boltzmann distribution][1], but I cannot decide on which temperature I should use in the equation.
For example, I have a very, very cold liquid (let's say 70 K) at room temperature (we'll call that 296.15 K), but wou... |
This question is a little bit broad, but thankfully, there are many resources available.
In answer to part of your question
> Which one is most suitable for packaging pastries, for example, biscuits?
The Natural Resources Defense Council webpage [Food Storage Containers][1], they state that the safest plasti... |
This question is a little bit broad, but thankfully, there are many resources available.
In answer to part of your question
> Which one is most suitable for packaging pastries, for example, biscuits?
The Natural Resources Defense Council webpage [Food Storage Containers][1], they state that the safest plasti... |
Is the following sequence of reactions correct?
$$\ce{CH2CH2 ->[][\ce{NH3},\,\ce{Na}] NaHC=CHNa}$$
$$\ce{NaCH=CHNa + 2CH3CH2Br-> CH3CH2CH=CHCH2CH3}$$
|
What can I do as a non-professional chemist that is legal?
If a license is not required, then what are the advantages to having one, such as ordering compounds, getting a job, etc.?
Thanks. |
Do I need a license or certificate to practice chemistry or what are the advantages if did have one? |
please explain how to derive magnetism of polyatomic molecules ? and if we derive it using an addition of Oxygen atom to oxygen ie O2 it will come to be paramagnetic like O2?? |
why is ozone O3 diamagnetic? |
Why would you want an expensive process to convert cheap molecules into other cheap molecules? Brominate ethane, make the organo-lithium, displace methyl iodide. Epoxidize ethylene, react with methyl lithium, eliminate to the olefin. Silly.
Doing something cheap, easy, and fast on a huge scale with unwanted methane... |
I am a second year mathematics student. I am mostly interested in statistics. Right now my curriculum doesn't offer me much choice (all second year courses are mandatory) but next semester I will be able to select the courses I want. Among the ones that are offered is a course called *Biochemistry*. It is actually a se... |
Biochemistry for a mathematics student? |
I am a second year mathematics student. I am mostly interested in statistics. Right now my curriculum doesn't offer me much choice (all second year courses are mandatory) but next semester I will be able to select the courses I want. Among the ones that are offered is a course called *Biochemistry*. It is actually a se... |
No, because for ethene, $pK_a = 44$. You won't be able to abstract even one proton.
Maybe, you were thinking in ethyne ($\ce{HC#CH})$? In that case, you are right! The bis-alkylation would work with sodium amide as a base!
But is the simultaneous abstraction of both protons the most plausible reaction then?
|
Please explain how to derive the magnetism of polyatomic molecules? and if we derive it using an addition of an oxygen atom to oxygen ie $\ce{O2}$ it will come to be paramagnetic like $\ce{O3}$? |
I'm trying to calculate the $\Delta\mathrm{G}$ of the following reaction. Are my calculations correct? I'm also a bit puzzled, 'cause this is a endoergonic reaction right? But the $\Delta\mathrm{G}$ is negative, so the reaction would be spontaneous if my calculations are correct and if the activation energy is reached ... |
$$ \Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$$
Gibbs Free energy does not only relate to the spontaneity of a reaction, the magnitude of Gibbs Free energy describes how much "free energy" is available, or how much work is possible.
$\Delta G^\circ$ can either be negative or positive even if $\Delta H^\ci... |
$$ \Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$$
Gibbs Free energy does not only relate to the spontaneity of a reaction, the magnitude of Gibbs Free energy describes how much "free energy" is available, or how much work is possible.
$\Delta G^\circ$ can either be negative or positive even if $\Delta H^\ci... |
How is Gold's atomic structure and bonding related to the separation techniques used to distinguish it from other substances? I found that the most common elements/compounds to be present in the slurry are:
| Silver |
Lead |
Zinc |
Copper |
Tellurium |
Quartz |
Calcite |
Pyrite |
I'm just confused on what ... |
$$ \Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$$
Gibbs Free energy does not only relate to the spontaneity of a reaction, the magnitude of Gibbs Free energy describes how much "free energy" is available, or how much work is possible.
$\Delta G^\circ$ can either be negative or positive even if $\Delta H^\ci... |
I'm trying to calculate the $\Delta\mathrm{G}$ of the following reaction. Are my calculations correct? I'm also a bit puzzled, 'cause this is a endoergonic reaction right? But the $\Delta\mathrm{G}$ is negative, so the reaction would be spontaneous if my calculations are correct and if the activation energy is reached ... |
According to Wikipedia 4-methyl-1-pentanol is $C_6H_{14}O$.
But here is what I got, which is slightly different.
Methyl = Think of methyl group, which is $CH_3$.
Pentanol = Penta means we have 5 carbons, $-ane$ ending means we have $2n+2$ hydrogens, i.e. 12 hydrogens and $-ol$ ending means we have a hydroxyl g... |
Molecular formula for 4-methyl-1-pentanol? |
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