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Presumptive test for modafinil? |
Reactions that are [autocatalytic](http://en.wikipedia.org/wiki/Autocatalysis) can have their rate increase as a function of conversion.
One example is the decomposition of cellulose acetate by hydrolysis, also known as [vinegar syndrome](http://en.wikipedia.org/wiki/Vinegar_syndrome#Decay_and_the_.22vinegar_syndrom... |
How do you find the pH of a solution with a known pK<sub>a</sub> and Molarity? |
How do you find the pH of a solution with a known pKa and Molarity? |
...but, most importantly, why? It's $$\ce{6e- +ClO_{3}^- +6H^+ \rightarrow Cl^- + 3 H_2O}$$
Now, with the gift of foresight, why was the equation for its oxidation not instead $$\ce {2e^- +ClO_{3}^- +2H^+ \rightarrow Cl^- + O_2+ H_2O}$$
? Obviously it balances and charge is conserved. However, the latter equation w... |
In an acid, what does $\ce{ClO_3-}$ reduce into? |
This one is troubling me and even got it wrong in my exam -:
at equilibrium the mas of reactants and products are equal, does that mean reaction stop?
Please explain this one. Thanks for help... |
At equilibrium the mas of reactants and products are equal, does that mean reaction stop? |
I would say the answer on [this website][1] is pretty near perfect.
To summarize, you need 2 things:
1. Enough friction between your nose and the spoon
2. The center of mass of the spoon should be on a line vertically downwards THROUGH the tip of your nose as illustrated in this image from the same website:
... |
> Cross post: http://physics.stackexchange.com/q/56800/7433
Last week I was discussing with a friend how we thought the stripeless cleaning of windows is achieved when using a cleaner like [Windex Glass Cleaner][1] as opposed to just using hot water, in which case you do get stripes left behind.
At first we thou... |
can some help me about this question please? |
Reactions that are [autocatalytic](http://en.wikipedia.org/wiki/Autocatalysis) can have their rate increase as a function of conversion.
One example is the decomposition of cellulose acetate by hydrolysis, also known as [vinegar syndrome](http://en.wikipedia.org/wiki/Vinegar_syndrome#Decay_and_the_.22vinegar_syndrom... |
According to my notes, [OCTAHEDRAL SITE STABILIZATION ENERGY (OSSE)], Sterrical effects and electronic effects in stability create a confusion in this theory. However, we are able to solve this problem with few rules;
1. Tetrahedral splitting energy is nearly equal to 4/9 Octahedral Splitting Energy.
2. As the OSSE ... |
According to my notes, [OCTAHEDRAL SITE STABILIZATION ENERGY (OSSE)], sterical effects and electronic effects in stability create a confusion in this theory. However, we are able to solve this problem with few rules:
1. Tetrahedral splitting energy is nearly equal to 4/9 Octahedral Splitting Energy.
2. As the OSSE... |
How, chemically, would you remove protruding phenyl groups? I mean for instance in the molecule phenethylamine there's a phenyl group sticking out (or protruding) how would you go about removing that phenyl group? |
How, chemically, would you remove protruding phenyl groups? |
How would you change the chirality of a compound such that (S,R) becomes (S,S)? That iss how would you synthesise a compound from its diastereomer? |
How would you change the chirality of a compound such that (S,R) becomes (S,S)? |
How would you change the chirality of a compound such that (S,R) becomes (S,S)? That is how would you synthesise a compound from its diastereomer? |
How, chemically, would you remove protruding phenyl groups? I mean for instance in the molecule phenethylamine there's a phenyl group sticking out (or protruding) how would you go about removing this phenyl group? |
I. e., what if we just burn trash completely or dissolve it in acid, get the resulting paste and extract pure chemical elements out of it by applying some physics and/or chemistry to it until no more can be extracted? Just curious. |
Can we process waste just by decomposing it to homogenous mass and extracting the elements from it? |
I. e., what if we just burn trash completely or dissolve it in acid, get the resulting paste and extract pure chemical elements out of it by applying some physics and/or chemistry to it until no more can be extracted? Just curious.
**EDIT**
To be perfectly clear: my main concern is whether there _are_ any means t... |
I am interested in the [Biological Half Life][BHL] of substances. In the previous wikipedia link, I've already found the half lives of common pharmaceutical products. I can't seem to find similar data for recreational substances, does anyone know these half lives?
[BHL]: http://en.wikipedia.org/wiki/Biological_half-... |
Do you know the formula:
$$pK_a = \frac{[H^+][A^-]}{[HA]}$$
?
You will need to find a concentration first, however, on the equation.
$$\ce{HA \rightleftharpoons H+ + A-}$$
And solve for the dissociated hydrogen ion, say x.
$$pK_a = \frac{[x][x]}{[HA]-x} = \frac{x^2}{[HA]-x}$$
The logic is: if x of ... |
I got a forcefield (OPLS-AA in this case) that lists lennard-jones parameters for all homonuclear van der waals interactions. Is there a way to deduct the heteronuclear vdw-interaction parameters from those? |
Can I deduct heteronuclear van der waals parameters from homonuclear parameters in a forcefield? |
According to my notes, [OCTAHEDRAL SITE STABILIZATION ENERGY (OSSE)], sterical effects and electronic effects in stability create a confusion in this theory. However, we are able to solve this problem with few rules:
1. Tetrahedral splitting energy is nearly equal to 4/9 Octahedral Splitting Energy.
2. As the OSSE... |
According to Wikipedia Caesiums density is 1,90 g/cm3 at T=20 °C. How does this change when T changes? E.g. will it expand when melting? |
How does Caesium's density change with temperature? |
I require Congo red indicator for an experiment I wish to perform involving dipping a cellulose sponge into an acid and a base. I first want to dye the cellulose sponge with Congo red, and observe the color change of the sponge as I place it in acids and bases.
Congo red apparently binds to cellulose and thus is su... |
Alternatives to Congo Red? |
I am in mathemmatics, but I am writing a paper on molecular vibrations (because you can use representationtheory to handle this).
I want to prove the selectionrule, but also I have to give a presentation of my intermediate results. Can someone give a little (maybe trivial) explanation (in one or maximal two small s... |
I am in mathematics, but I am writing a paper on molecular vibrations (because you can use representation theory to handle this).
I want to prove the selection-rule, but I also have to give a presentation of my intermediate results. Can someone give a little (maybe trivial) explanation (in one or maximal two small s... |
According to Wikipedia Caesium's density is 1,90 g/cm3 at T=20 °C. How does this change when T changes? E.g. will it expand when melting? |
I am not sure how sharpness is measured, but I do know that certain materials can be designated sharper than others, for example [obsidian is said to be the sharpest material][1]:
> The prismatic glass blade is infinitely sharper than a honed steel edge
So my question is, will a honed edge of high-tin bronze be s... |
Can high-tin bronze be made sharper than low-tin bronze? |
When people talk about oxides like SiO2 or Al2O3, they use expressions like stoichiometric or under-stoichiometric. I understand that this refers to the relative composition of materials, but I don't really know what it exctly means?
Say for SiO2, does under-stoichiometric mean that it isn't exactly SiO2, but more l... |
What does under-stoichiometric or stoichiometric mean? |
Is there a specific term for reactions of the form $\ce{A + B -> C + D}$? |
When people talk about oxides like $\ce{SiO2}$ or $\ce{Al2O3}$, they use expressions like stoichiometric or under-stoichiometric. I understand that this refers to the relative composition of materials, but I don't really know what it exctly means?
Say for $\ce{SiO2}$, does under-stoichiometric mean that it isn't exa... |
Do you know the formula:
$$K_a = \frac{[H^+][A^-]}{[HA]}$$
?
You will need to find a concentration first, however, on the equation.
$$\ce{HA \rightleftharpoons H+ + A-}$$
And solve for the dissociated hydrogen ion, say x.
$$K_a = \frac{[x][x]}{[HA]-x} = \frac{x^2}{[HA]-x}$$
The logic is: if x of HA... |
I'd like to add some things to what Tanith Rosenbaun said.
First, the point of *net* ionic equations is not just to write out the equations in terms of ions, but to focus on only those ions that experience a change in charge or valence. Ions which don't change in charge don't really participate in the reaction and ... |
Magnesium, oxygen and magnesium oxide form the above equation.
1. How?
2. What do I need to learn to do this? atomic numbers/ valencies? |
Mg + O2 → MgO [how it forms]? |
First of all, do you know that chemical equations are means to express chemical reactions?
Second, this equation represents the reaction of magnesium with oxygen. Magnesium and Oxygen are the reactants and Magnesium Oxide is the product.
The arrow indicates the direction of the reaction.
To write basic chemi... |
$\ce{Mg + O2 → MgO}$
Magnesium, oxygen and magnesium oxide form the above equation.
1. How?
2. What do I need to learn to do this? atomic numbers/ valencies? |
How does the reaction Mg + O2 → MgO occur? |
Homemade preservative for natural aloe-vera gel? |
A friend of mine gave me a bottle of home-made liquor which is a concoction of pure alcohol and sweetened milk. I accepted his gift happily and then I put the bottle in my cocktail cabinet. After an hour, we happened to hear a terrible noise of a some sort of explosion. We were indeed right - the bottle had exploded wi... |
Can an isolated system(of several phases) in equilibrium by itself move out of equilibrium?
if a system contains for example an inflammable gas dispersed with another combustible gas such that the molecular speed are insufficient to cause the reaction. but as the molecular speeds keep fluctuating, at some point, it ma... |
Can an isolated system(of several phases) in equilibrium by itself move out of equilibrium?
if a system contains for example an inflammable gas dispersed with another combustible gas such that the molecular speed are insufficient to cause the reaction. but as the molecular speeds keep fluctuating, at some point, it ma... |
I'm asked to find the Lewis Structure of sulfuric acid, $SO_4H^-$. After struggling for a while, I sumply looked it up.
![Source: Wikipedia][1]
How can this be? Sulfur has 6 electrons in its valence shell, so it should form bonds so as to collect 2 more electrons and satisfy the octet rule. So, surely it should ... |
The question title is a bit odd, I couldn't find a plainer way of saying it.
I'm given the concentration and conductivity of a solution of a particular acid, let's just call it AH. I then have to deduce that acid's acidity constant.
My first instinct is to write out the expression for the solution's conductivity.... |
How am I to interpret the phrase "a solution of acid"? |
If I have an expression for the Helmholtz free energy (from statistical associating fluid theory for a polymer system), can I still find the Gibbs free energy minimum under constant T,p conditions?
Seems that since
$\mu_i = \left(\frac{\partial A}{\partial n_i}\right)_{T,V,n_j} = \left(\frac{\partial G}{\partia... |
I know this is simple, compared to most questions asked here, but I notice this several times a week and I'm curious.
I notice if I break an egg and drop it into the frying pan, and the pan is still warming up, the egg sticks to the pan. But if I wait until the pan is quite hot, and I break an egg and drop it in, t... |
At standard conditions(at 1atm pressure and unit activity(1molal or 1molar concentration)of all dissolved compounds),the electrode potential is equal to the standard electrode potential by the Nernst equation. $$ \Delta E = \Delta E^0 $$
At the same time,while the electrochemical reaction is at equilibrium,the electro... |
Standard electrode potential of a galvanic half cell is zero at equilibrium at standard conditions? |
I'm familiar with the periodic table / periodic system, but I wonder why it's called "periodic" since there seems not much periodic about (there seems to be little or no predictability of which elements are stable) and from physics I know Z-value of elements and that is not periodic either. So what is a "period" in thi... |
What is a "period" of the periodic table? |
which chemical element has the lowest boiling point?
Is it Helium(He) or is it Hydrogen(H)?
Hydrogen is lighter than Helium. |
which chemical element has the lowest boiling point? |
In theory you should be able to turn $\ce{CO2}$ to $\ce{CO}$ and then to $\ce{C}$ and connects all the C-atoms together to form graphene.
That should be possible, because plants do something similar, they take $\ce{H2O}$ and $\ce{CO2}$ and links the C-atoms together as $\ce{C6H12O6}$
Is it possible to produce grap... |
Why do frying pans stick less with heat? |
If I have an expression for the Helmholtz free energy (from statistical associating fluid theory for a polymer system), can I still find the Gibbs free energy minimum under constant $T,P$ conditions?
Seems that since
$\mu_i = \left(\frac{\partial A}{\partial n_i}\right)_{T,V,n_j} = \left(\frac{\partial G}{\part... |
This one is troubling me, and I even got it wrong in my exam:
at equilibrium the mass of reactants and products are equal, does that mean the reaction stops?
Please explain this one. |
At equilibrium, the mass of reactants and products are equal. Does that mean the reaction stops? |
Can someone explain the following types of molecules and predict their structure and shape?
It will help my understanding if you could provide an example.
AX3E,AX5 and AX6
note that A = central atom and X = bonding atoms.
|
https://i.stack.imgur.com/tpScm.png I have no clue what the substituent may be, help!!
The molar mass of the unsubstituted benzaldehyde is 105g/mol (subtracting one H, where the substituent will be). So the substituent is around 30-33g/mol. Also I'm having trouble identifying the molecular ion. Is it the really smal... |
What is the substituent on this benzaldehyde? (MS attached) |
![enter link description here][1]
I have no clue what the substituent may be.
The molar mass of the unsubstituted benzaldehyde is 105g/mol (subtracting one H, where the substituent will be). So the substituent is around 30-33g/mol. Also I'm having trouble identifying the molecular ion. Is it the really small 138 ... |
In my textbook, for calculating the percentage dissociation of $HF$ for the given equation:
$$\ce{HF + H2O <-> H3O+ + F-}$$
The solution is:
Initial Concentrations
$$[\ce{HF}] = 0.08M, \: \ce{[H3O+]} = 0, \:\ce{[F- ]}= 0$$
Equilibrium concentrations
$$[\ce{HF}] = 0.08M - x, \: \ce{[H3O+]} = x, \:\ce{[F- ]}= x... |
The molecular ion $\ce{[M]^{\bullet +}}$ peak is likely at 136 m/z. The peak at 137 m/z is due to the 1.1% natural abundance of [$\ce{^{13}C}$][1].
The peak at 135 m/z is the $\ce{[M-1]^{+}}$ peak typical of aldehydes:
$$\ce{ [R-C(=O)-H]^{\bullet +} -> [R-C+=O <-> R-C\equiv O+] +H ^{\bullet} }$$
Another typic... |
Water ($\ce{H2O}$) is a dipole. The reason why is simply because it is not symmetrical, and there are more electrons on the oxygen side than on the hydrogen side.. (Also because of the electronegativity.)
But why isn't $\ce {H_{2}O}$ symmetrical like $\ce{CO2}$? Why isn't $\ce{H2O}$ non polar like $\ce{CO2}$? Does i... |
How to find the valencies of elements by using it's distribution of electrons?
Explain the method in simple words?
Do you have to study the valencies or is there is a simple way of remembering?
PS: There is supposed to be some method of getting the valency after knowing the distribution of electrons.
Example:
e... |
How to get the valencies of elements? |
> So what is a "period" in this context?
To answer this directly, **a period is a row of the table.**
As trb456 indicates, the repeating periods reflect the filling-up of atomic orbitals. Because the valence electrons (those in the outer shell of an atom) determine many of the chemical properties, the periodic stru... |
I need to 'adhese' paper to plastic, but I need the adhesive to be flammable and quick burning, but without producing any ash or too many toxic fumes.
I know this is an absurd question, but does anything like this exist?
Thanks so much
|
why does the melting point gets lower down the Alkali Metal Group with increase in atomic number?
The atomic radius increases. |
why does the melting point gets lower down the Alkali Metal Group with increase in atomic number? |
> So, I ask, what are the trends leading to the brittleness of a metal
[Brittle] materials absorb very little energy before fracturing. The only trend that can be linked to this is the strength of bonding in the metal (Other factors like crystal structure and purity do not have any trends and so there are a lot of e... |
> So, I ask, what are the trends leading to the brittleness of a metal
[Brittle] materials absorb very little energy before fracturing. The only trend that can be linked to this is the strength of bonding in the metal (Other factors like crystal structure and purity do not have any trends and so there are a lot of e... |
Why does the melting point get lower going down the Alkali Metal Group with increase in atomic number?
|
Why does the melting point get lower going down the Alkali Metal Group with increase in atomic number? |
I am considering making a sheet of graphene using the LightScribe technique and I have read that I need graphite oxide. However when I look up graphite oxide for sale, graphene oxide pops up.
Are these two oxides similar? What is the difference? |
What is the difference between graphite oxide and graphene oxide? |
Is there a technical difference between the terms "autocatalysis" and "chain reaction"? They both seem to refer to something very similar, namely sequences of reactions in which one of the intermediates is also one of the products, leading to the possibility of exponential growth. Is one of the terms more specific than... |
An [autocatalytic reaction][1] is a reaction where the product catalyzes the reaction. An autocatalytic reaction takes the following form (or more complex variations of it).
$\ce{A + B -> 2B}$
An autocatalytic reaction must produce the exact species $\ce{B}$ that cataylzes the reaction. More about autocatalytic... |
I don't know about the IR spectra of metals. Certainly metals will have vibrational spectra, but I'm sure where to find it (if NIST does not have).
**I can tell you how to get x/y data from NIST**, if they have the spectrum.
For example, for [benzoic acid][1]. At the bottom of the page, there is a link to [downlo... |
I'm studying for my final exam, and these are the questions I got wrong on the mid term, could anyone help correct me? I know people are against giving answers for homework, so I must add that is now exam period for Universities, so this is only for my further understanding!
Thanks so much!
1)The pH of a 0.2M unkno... |
I'm studying for my final exam, and these are the questions I got wrong on the mid term, could anyone help correct me? I know people are against giving answers for homework, so I must add that is now exam period for Universities, so this is only for my further understanding!
Thanks so much!
----------
My at... |
I'm struggling with this homework question:
"For a parallel reaction A goes to B with rate constant k1 and A goes to C with rate constant k2, you determine that the activation energies are 71.9 kJ/mol for k1 and 142.8 kJ/mol for k2. If the rate constants are equal at a temperature of 321 K, at what temperature (in K) ... |
Of all the elements in periodic table, which one has smallest nearest neighbor distance? I tried searching on net, but could not find any reference. My earlier guess was one which goes into FCC with smallest unit cell dimension should be one. But I am not sure. |
I'm struggling with this homework question:
"For a parallel reaction A goes to B with rate constant $k_1$ and A goes to C with rate constant $k_2$, you determine that the activation energies are 71.9 kJ/mol for $k_1$ and 142.8 kJ/mol for $k_2$. If the rate constants are equal at a temperature of 321 K, at what tempera... |
Of all the elements in periodic table, which one has smallest nearest neighbor distance? I tried searching on net, but could not find any reference. My earlier guess was one which goes into FCC with smallest unit cell dimension should be one. But I am not sure.
In an FCC, if unit cell dimension is a, then nearest ne... |
**Complex structure**
[Modafinil][1] is a pretty complex molecule and judging by its structure (see below) I think it will be extremely difficult to find a single reagent test that will identify it.
![enter image description here][2]
**Post-consumption identification**
Interestingly it is much easier to fin... |
Is there a technical difference between the terms "autocatalysis" and "branching chain reaction"? They both seem to refer to something very similar, namely sequences of reactions in which one of the intermediates is also one of the products, leading to the possibility of exponential growth. Is one of the terms more spe... |
Can an isolated system(of several phases) in equilibrium by itself move out of equilibrium?
if a system contains for example an inflammable gas dispersed with another combustible gas such that the molecular speed are insufficient to cause the reaction. but as the molecular speeds keep fluctuating, at some point, it ma... |
Spontaneous inequilibrium in a gas in an isolated system? |
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