instruction stringlengths 15 21.8k |
|---|
I was trying to calculate amount of salt needed to lower the melting point of water by 5°C. According to my solutions, I need to make sure $$n\mu(\ce{H2O(s)}) =n\mu(\ce{H2O(l)})+ RT\log(x)$$where $ x=\frac{n}{n+2m}$
I however thought that I need to make sure that
$$n\mu(\ce{H2O(s)})+m\mu(\ce{NaCl(s)}) =n\mu(\ce{H... |
So, I would like to ask the addition of TFA in Pfitzner Moffat oxidation is to protonate the DCC to form a positive carbocation for the alcohol to attack? Or is there more to it? Why is TFA used and not other acids? Are other acids to weak for this?
Lastly for the Collins vs Jones Oxidation, the only discernible dif... |
In a section discussing **Miller indices**, my textbook says the following:
> The rules for determining the Miller indices of a direction or an orientation in a crystal are as follows: translate the orientation to the origin of the unit cell, and take the normalized coordinates of its other vertex.
What I'm conf... |
Miller indices: How does one translates the orientation to the origin of the unit cell? |
In a section discussing **Miller indices**, my textbook says the following:
> The rules for determining the Miller indices of a direction or an orientation in a crystal are as follows: translate the orientation to the origin of the unit cell, and take the normalized coordinates of its other vertex.
What I'm conf... |
I'm part of a rocket building team and I'm working with propellants. We use saltpeter as the oxidizer, bought as fertilizer and purified by recrystallization. Recently we bought it from another source, that identified the chemical as potassium nitrate, as usual, but when we heated it to make the propellant it simply me... |
My doubt is very basic but I have referred to a couple of books before asking this question
This is an excerpt from Linus Pauling's book:
*"the most probable distance of the electron from
the nucleus, which is the value of r at which D(r) has its maximum
value, is seen from Figure 21-1 to be a=0.529A, which is ju... |
My doubt is very basic but I have referred to a couple of books before asking this question
This is an excerpt from Linus Pauling's book:
*"the most probable distance of the electron from
the nucleus, which is the value of r at which D(r) has its maximum
value, is seen from Figure 21-1 to be a=0.529A, which is ju... |
My question is regarding Swern oxidation. Why is the methyl group of the DMSO deprotonated and not directly the red hydrogen atom of the R2-CH-O bond deprotonated? Shouldn't it be that oxygen more electronegative (stronger -I effect) than sulfur and shouldn't that make that corresponding hydrogen atom more acidic? Or i... |
Usage of TFA in Pfitzner Moffat oxidation and Collins vs Jones oxidation? |
Is the addition of TFA in Pfitzner-Moffat oxidation to protonate the DCC to form a positive carbocation for the alcohol to attack? Or is there more to it? Why is TFA used and not other acids? Are other acids to weak for this?
Lastly for the Collins vs Jones oxidation, the only discernible differences are the solvent... |
I was trying to calculate amount of salt needed to lower the melting point of water by 5 °C. According to my solutions, I need to make sure $$n\mu(\ce{H2O(s)}) =n\mu(\ce{H2O(l)})+ RT\log(x)$$where $ x=\frac{n}{n+2m}$
I, however, thought that I need to make sure that
$$n\mu(\ce{H2O(s)})+m\mu(\ce{NaCl(s)}) =n\mu(\c... |
I make a **thermal actuator** that works with the expansion of diethyl ether at its boiling point of around 34 °C. For sealing and lubrication of the polypropylene piston and barrel, I need **a lubricant that is immiscible with diethyl ether and does not react with it**.
I found that diethyl ether is slightly solub... |
What lubricant can be used for mechanical parts in a system containing diethyl ether? |
It is very important to note here that $R(r)$ is just the radial part of *wavefunction*. Wavefunction does not describe any observable. The Born interpretation says that the probability **density** of finding electron between any two points $x_1$ and $x_2$ is given by
$$\rho=\psi\psi*$$
While the probability is
$$P =\... |
It is very important to note here that $R(r)$ is just the radial part of *wavefunction*. Wavefunction does not describe any observable. The Born interpretation says that the probability **density** of finding electron between any two points $x_1$ and $x_2$ is given by
$$\rho=\psi\psi*$$
While the probability is
$$P =\... |
According to Chembuddy, the formula for theoretical buffer capacity for a monoprotic buffer system is as follows:
> $$β = 2.303\left(\frac{K_\mathrm{w}}{[\ce{H+}]} + [\ce{H+}] + \frac{C_\mathrm{buf}K_\mathrm{a}[\ce{H+}]}{(K_\mathrm{a} + [\ce{H+}])^2}\right)$$
where $C_\mathrm{buf}$ is the total concentration of b... |
It is very important to note here that $R(r)$ is just the radial part of *wavefunction*. Wavefunction does not describe any observable. The Born interpretation says that the probability **density** of finding electron between any two points $x_1$ and $x_2$ is given by
$$\rho=\psi\psi*$$
While the probability is
$$P =\... |
As Jan wrote, there isn't a hard and fast rule encompassing every mechanism, so there may not be a definitive answer to the question. Nevertheless, I found an interesting site that talked a little bit about the Finkelstein reaction:
$$\ce{NaI + RX -> NaX + RI}\qquad\ce{X} = \ce{Cl}, \ce{Br}$$
This is in acetone ... |
A question for the masses about standard deviation, selection of population vs sample in balance measurements.
Analytical balances are typically checked for repeatability by taking 10 weight measurements and finding the uncertainty by calculating standard deviation.
There are two forms of standard deviation; popu... |
I am attempting to prepare potassium tert-butoxide. I was going to suspend anhydrous toluene and anhydrous tert butanol, dissolve (reflux) the potassium metal (pure), then distill the excess tert butanol as a benzene azeotrope.
2 questions.
1. The medal is coming in mineral oip should I rinse it and toluene to ... |
A question for the masses about standard deviation (SD), selection of population vs sample in balance measurements.
Analytical balances are typically checked for repeatability by taking 10 weight measurements and finding the uncertainty by calculating standard deviation.
There are two forms of standard deviation:... |
I am attempting to prepare potassium *tert*-butoxide. I was going to suspend anhydrous toluene and anhydrous *tert*-butanol, dissolve (reflux) the potassium metal (pure), then distill the excess *tert*-butanol as a benzene azeotrope.
2 questions.
1. The medal is coming in mineral oil should I rinse it and tolue... |
I am attempting to prepare potassium *tert*-butoxide. I was going to suspend anhydrous toluene and anhydrous *tert*-butanol, dissolve (reflux) the potassium metal (pure), then distill the excess *tert*-butanol as a benzene azeotrope.
2 questions.
1. The metal comes stored in mineral oil. Should I rinse it in to... |
I have the following question:
20mL of sulfur vapour at 1000°C reacts with 40mL of oxygen gas to form 40mL of sulfur dioxide gas. Determine the number of atoms in the molecule of sulfur in the vapour state at this temperature.
My working out is as follows:
S + O2 -> SO2 (all in gaseous state)
20mL + 40mL ... |
How to calculate the number of atoms in gaseous quantities at a certain temperature? |
How can spike recovery be over 100%? |
**Freezing**
>I've heard that the freezing and boiling points of the mixed liquid would exist on some continuum between the freezing and boiling points of its constituent liquids (ammonia and water), varying depending on the exact mix ratio and of course pressure. Is that correct?
For freezing points, that is inc... |
I have the following question:
20mL of sulfur vapour at 1000°C reacts with 40mL of oxygen gas to form 40mL of sulfur dioxide gas. Determine the number of atoms in the molecule of sulfur in the vapour state at this temperature.
My working out is as follows:
S + O2 -> SO2 (all in gaseous state)
20mL + 40mL ... |
I want to purify IgG which has a theoretical pI of 6.4-9.0 with an anion exchange column. I also want to keep the pH of my buffers as low as possible and "outside" the range of the pI to prevent aggregation.
Still, I will need to increase the pI so that IgG will have negative net charge and bind to the column. What ... |
> $\pu{20 mL}$ of sulfur vapour at $\ce{1000 °C}$ reacts with $\pu{40 mL}$ of oxygen gas to form $\pu{40 mL}$ of sulfur dioxide gas. Determine the number of atoms in the molecule of sulfur in the vapour state at this temperature.
My working out is as follows:
$$\ce{\underset{\pu{20 mL}}{S(g)} + \underset{\pu{40 m... |
**Question: Is it oxygen or fuel that releases energy during burning?**
The surprising answer from this article:
[Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2 (ACS Publications, 2015)][1]
> Our analysis provides simple answers to two related, important
> questions: “What makes ... |
Does energy come from fuel or oxygen? (surprise?) |
**Question: Is it oxygen or fuel that releases energy during burning?**
The surprising answer from this article:
[Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2 (ACS Publications, 2015)][1]
> Our analysis provides simple answers to two related, important
> questions: “What makes ... |
**Question: Is it oxygen or fuel that releases energy during burning?**
The surprising answer from this article:
[Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2 (ACS Publications, 2015)][1]
> Our analysis provides simple answers to two related, important
> questions: “What makes ... |
**Question: Is it oxygen or fuel that releases energy during burning?**
The surprising answer from this article:
[Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2 (ACS Publications, 2015)][1]
> Our analysis provides simple answers to two related, important
> questions: “What makes ... |
As apparent, the molar ratio of sulfur to oxygen in the reactants is $1:2$, which would make sulfur the limiting reagent and ultimately 1 part of $\ce{SO2}$ would form, amounting to $20~\pu{mL}$ only. That tells us that we need to consider sulfur in its **$\beta$-octasulfur state**. It might be wrongly assumed that oct... |
> $\pu{20 mL}$ of sulfur vapour at $\pu{1000 °C}$ reacts with $\pu{40 mL}$ of oxygen gas to form $\pu{40 mL}$ of sulfur dioxide gas. Determine the number of atoms in the molecule of sulfur in the vapour state at this temperature.
My working out is as follows:
$$\ce{\underset{\pu{20 mL}}{S(g)} + \underset{\pu{40 m... |
I recently went to a market in Southern France and found this little piece of equipment for sale along with a whole bunch of other chemistry things. the guy had no idea what it was for or where he'd gotten it from, but for €1 I decided I had to have it because I've never seen anything quite like it (and I'm mildly infa... |
Identifying Name/Purpose of piece of ellipsoid glassware with internal tube? |
What is phase separation basically? |
**Question: Is it oxygen or fuel that releases energy during burning?**
The answer from this article:
[Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2 (ACS Publications, 2015)][1]
> Our analysis provides simple answers to two related, important
> questions: “What makes fire hot?” ... |
Does a complex that has no overall charge still have color? |
By exporting some search results from Reaxys, I found "Reaction rank" to be one of the columns in the Excel file. In my file, values descend from 107 to 52 and skip some values in-between too. Does anyone know what reaction rank stands for here? |
"The expression that correlates the rate of reaction with concentration of reactants is known as rate law for that reaction."
So the rate law only include the concentration of reactants, not products.
But the rate law for this reaction is: $$\ce{r=k[O3]^2[O2]^{-1}}$$ where k is rate constant.
"Order of a reaction ... |
How is the 'rate law' and 'order' for the following reaction can be defined? $$\ce{2O3 -> 3O2}$$ |
As apparent, the molar ratio of sulfur to oxygen in the reactants is $1:2$, which would make sulfur the limiting reagent and ultimately 1 part of $\ce{SO2}$ would form, amounting to $20~\pu{mL}$ only. That tells us that we need to consider sulfur in its **$\beta$-octasulfur state**. It might be wrongly assumed that oct... |
How is the 'rate law' and 'order' for the following reaction can be defined?
$$\ce{2O3 -> 3O2}$$
"The expression that correlates the rate of reaction with concentration of reactants is known as rate law for that reaction."
So the rate law only include the concentration of reactants, not products.
But the rate ... |
How is the 'rate law' and 'order' for the ozone decomposition reaction can be defined? |
Whatever contamination in your tap water should be a great deal less than the concentration of CuSO4, but might be a factor in your experiment.
Conductivity is measured using a non-depositing AC current. The DC resistance or its inverse will depend on many factors, but all will require a measurement of voltage and c... |
Boyle's Law states that:
Pressure is inversely propotional to Volume.
But if we take an example of a balloon. As we fill air in it it's pressure increases but it's volume also increases.
[![][1]][1]
<sub>(source: [ucdavis.edu](http://chemwiki.ucdavis.edu/@api/deki/files/8673/Red_Balloon_Effusion.JPG?size=best... |
Boyle's Law states that pressure is inversely proportional to volume.
However, let's take an example of a balloon: as we fill air in it, its pressure increases, but its volume also increases. Can anyone explain?
[![][1]][1]
<sub>(source: [ucdavis.edu](http://chemwiki.ucdavis.edu/@api/deki/files/8673/Red_Balloo... |
So i was studying chemical bonding where i noticed something odd.
We say compounds like $CCl_4$ and $CH_4$ have a tetrahedral geometry ( which is a 3D structure) but when we talk about their dipole moments , we say they have 0 dipole moment in which we give the reason that as the H atoms are opposite each other ( henc... |
Why does a tetrahedral have a 0 dipole moment? |
We use Scherrer's equation to calculate crystalline size of a particle:
$$d = \frac{Bλ}{β\cos{θ}}$$
But which theta should we take from the XRD pattern for this calculation?
For example, the following plot shows the diffraction pattern of nano (above) and bulk (below) silicon and it has two diffraction peaks a... |
Which theta should be taken from x-ray diffraction pattern for calculating Scherrer's equation? |
> {OP:] It is usually said that fuel contains energy and that oxygen only enables the release of energy in the sense like enzymes enable reactions.
An enzyme is a catalyst, so it does not change the enthalpy of a reaction. That part is correct. "Oxygen only enables the release of energy" is incorrect. Oxygen is one ... |
**Question: Is it oxygen or fuel that releases energy during burning?**
The answer from this article:
[Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2 (Journal of Chemical Education, 2015)][1]
> Our analysis provides simple answers to two related, important
> questions: “What make... |
I have seen phase separation as a phenomenon taking place. However I do not understand why this phenomenon occurs as a counter example to the natural laws of diffusion along the concentration gradient. During phase separation the richer side becomes richer with the atoms which it already has and becomes more and more d... |
What is the reason for phase separation? |
Whenever I am to prove the fact that the $y$ intercept to the $G$ vs $X$ curve is basically my chemical potential, there are two equations that need to be assumed. One is
$$G=\mu _{A}X_{A}+\mu _{B}X_{B},$$
and the other is the total differential expression of $\mathrm{d}G'$. However they are treated as two independ... |
My question is basic, but I have already referred to a couple of books.
This is an excerpt from Linus Pauling's book:
>the most probable distance of the electron from the nucleus, which is the value of $r$ at which $D(r)$ has its maximum value, is seen from Figure 21-1 to be $a=\pu{0.529 \mathring{A}}$, which is ju... |
I was studying chemical bonding when I noticed something odd.
We say compounds like $\ce{CCl4}$ and $\ce{CH4}$ have a tetrahedral geometry (which is a 3D structure) but when we talk about their dipole moments, we say they have no dipole moment. We give the reason that as the H atoms are opposite each other (hence as... |
Why does a tetrahedral molecule like methane have a dipole moment of zero? |
It is very important to note here that $R(r)$ is just the radial part of *wavefunction*. Wavefunction does not describe any observable. The Born interpretation says that the probability **density** of finding electron between any two points $x_1$ and $x_2$ is given by
$$\rho=\psi\psi^*.$$
While the probability is
$... |
According to Wikipedia, silicon has a Pilling-Bedworth ratio of 2.15. In theory this should mean an SiO2 film on silicon should have a fairly large amount of compressive stress and high probability of fracturing. After all, 2.15 is even higher than the 2.14 PB ratio of iron, which flakes quite readily as rust. However ... |
Why doesn't the Pilling-Bedworth ratio of silicon cause issues in silicon technology? |
From a biological system, I got the following reaction:
$$A+B+D\rightarrow C+C_1D$$ ($C_1D$ is a certain complex)
However, if at any given time there are no $D$s to react, and **only** then, instead the following reaction does happen (until a new $D$ appears, when the first reaction switches instead):
$$A+B\ri... |
From a biological system, I got the following reaction:
$$A+B+D\rightarrow C+C_1D$$ ($C_1D$ is a certain complex)
However, if at any given time there are no $D$s to react, and **only** then, instead the following reaction does happen (until a new $D$ appears, at which point the first reaction switches in instead)... |
I have seen phase separation as a phenomenon taking place. However I do not understand why this phenomenon occurs as a counter example to the natural laws of diffusion along the concentration gradient. During phase separation the richer side becomes richer with the atoms which it already has and becomes more and more d... |
Is there free software which can calculate the fluorescence emission spectra of organic molecules?
Let's say for example: rubrene
There is a bunch of quantum free quantum chemistry software:
https://en.wikipedia.org/wiki/List_of_quantum_chemistry_and_solid-state_physics_software
However, which one would be the m... |
How to calculate molecular emission spectra? |
I will need a fluid around a specific viscosity, using a mixture of water and something like sugar.
Is there a way to calculate viscosity based on concentration? |
The equilibrium constant(EC) of a certain reaction is only dependent on temperature. For instance, suppose at a certain temperature, the EC of A+3B=2C is K. Now if I divide the whole equation by 2 to get (1/2)A+(3/2)B=C, why will my new EC K' be the square root of the previous one,namely K?. |
Internet consensus seems to define "high concentration" for Beer's Law as >0.01M. If one has a solution at higher concentrations than that, but the absorbance vs. concentration is still linear, is it valid to use Beer's Law to calculate concentration from absorbance data (assuming that the concentration is less than th... |
If Beer's Law appears to apply to a high concentration (>0.01M) of a solute, is it valid to use for concentration calculation? |
I balanced the chemical reaction which is as follows:
NaCl + KHCO3 = NaHCO3 + KCl
I've also gathered solubility values which are the following:
- KHCO3
22.4 g/100 mL (20 °C)
- NaCl
35,9 g/100 mL (20°)
- KCl
34.2 g/100ml (20°C)
- NaHCO3
9.6 g/100ml (20 °C)
Since NaHCO3 is less soluble than the ot... |
Is it possible to produce sodium carbonate from potassium carbonate? |
Recently I came across nonbonding orbitals. I know somethings about bonding and antibonding orbitals and there formation. But i have no idea about nonbonding orbitals.Can anyone explain there formation and there difference with the other two? |
In basic MO theory, when two atomic orbitals mix, they form an in-phase (bonding) and out-of-phase (antibonding) molecular orbital. The primary criteria for this mixing are having the same symmetry and being near in energy. If you mix your atomic orbitals together, but find that some of the atomic orbitals have no symm... |
Positive deviations are when the measured mass is more than the true mass of the sample and negative deviations are when the measured mass is less than the true mass of the sample. What steps causes this type of errors in analytical measurements? |
What causes positive and negative deviations when weighing analytical samples? |
>10 g of substance below were dissolve in each 1L water
>Na2SO4
>NaCl
>Glucose
>MgCl2
>Which one has the highest BP?
Glucose has London dispersion force
Na2SO4, NaCl, MgCl2 have ionic forces
Ionic forces is stronger than London dispersion force
So Na2SO4, NaCl, MgCl2 have higher BP than Glucose
Now, how to... |
Which one has the highest BP? |
Recently I came across nonbonding orbitals. I know something about bonding and antibonding orbitals and their formation, but I have no idea about nonbonding orbitals. Could someone explain their formation and the difference when compared with the other two? |
In the last step of Kjeldahl method, the unreacted HCl in the solution is back titrated with a standard NaOH and the concentration of HCl that has been used to neutralize the ammonia is then calculated. However, other than HCl there also exist an acid in the solution that can be titrated with NaOH which is the protonat... |
In the last step of Kjeldahl Method, is the reaction of ammonium to NaOH not taken into account? |
> 10 g of substance below were dissolve in each 1 L water:
> $\ce{Na2SO4}$
> $\ce{NaCl}$
> Glucose
> $\ce{MgCl2}$
> Which one has the highest boiling point?
Glucose has London dispersion force.
$\ce{Na2SO4},$ $\ce{NaCl},$ $\ce{MgCl2}$ have ionic forces.
Ionic forces is stronger than London dispersio... |
Which one has the highest boiling point? |
> "In the beginning we saw that [methane molecules] are 3D structures with one H being at the top and other 3 at the bottom, with the bond dipole moment directed from each H towards C. Due to this the component of the bond moment of the 3 downward H atoms along the line of the upper H atom would cause a net upwards bon... |
I am fairly new to anodization of Titanium. It concerns anodization using oxalic acid with the sole purpose of coloring Titanium grade 2 parts (= type III?). After some research online, I found a lot of information on the required voltage levels per color. However, to my understanding, the "purpose" of the voltage is o... |
According to entropy and gibbs free energy, randomness is one of the factors that determines reaction spontaneity, but why? Shouldn't it be the opposite? |
Why does a system want to achieve randomness to be feasible? |
You may need to think outside chemistry a little bit and pay a little bit attention to your everyday life. This is what happened when you boil water in a container:
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/qagYc.jpg
Most hardness in water, calcium/magnesium, will precipitate ont... |
Remember asking my chemistry teacher this question in 1979/80: in the reduction of 1,3-dinitrobenzene with hydrogen sulphide/ aqueous ammonia, why is only one nitro group reduced?. He said that the reaction must be driven by the electon-depleted ring (two nitro groups); as one nitro-group becomes an amino, electron den... |
I balanced the chemical reaction which is as follows:
NaCl + KHCO3 = NaHCO3 + KCl
I've also gathered solubility values which are the following:
- KHCO3
22.4 g/100 mL (20 °C)
- NaCl
35,9 g/100 mL (20°)
- KCl
34.2 g/100ml (20°C)
- NaHCO3
9.6 g/100ml (20 °C)
Since NaHCO3 is less soluble than the othe... |
Is it possible to produce sodium bicarbonate from potassium bicarbonate? |
I have a plasma consisting of elements A and B. These elements can react to form molecules AB.
$$
\ce{A + B -> AB}
$$
Now if my plasma or gas is expanding based on pressure gradients, I will have some sort of diffusion of these two element concentrations. Based on my spectroscopic analysis, the rate of decay of... |
Is there a known relation between the diffusion of a molecule and the diffusion of the reactants? |
[![enter image description here][1]][1]
The point marked 1 and 2 are basically the compositions of two metal alloys that have been welded.Now annealing is performed at a particular temperature T1 to bring about the change now why will A atoms diffuse from $\beta$ phase to $\alpha$ phase and B atoms from $\alpha$ phase... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.