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6
votes
2answers
37k views

How to calculate the formal charge of sulfate ion?

I found a site with this formula if you will, Formal Charge = [Number of valence electrons on atom] – [non-bonded electrons + number of bonds] I don't think I am using it correctly in finding the ...
2
votes
1answer
2k views

Figuring out the volume of air trapped inside a bottle of water

I am doing a chemistry lab report on figuring out the volume of air trapped inside a bottle. Here is the procedure: Fill a larger container or tub about half full with tap water Fill a 2 L plastic ...
3
votes
2answers
456 views

Equilibrium constant

I know that equilibrium constant depends on temperature and pressure. But according to Le Chatelier's principle when we change pressure of reagents the equilibrium is the same. Why?
6
votes
2answers
2k views

Why does molten plastic (PLA) stick to metals (AL)?

I know this is broad so I will narrow: Why does molten PLA stick to Aluminum? I ask because I'm looking for a way to prevent/reduce the friction of the plastic inside the aluminum barrel of a 3D ...
4
votes
1answer
3k views

Why does the extent of racemisation in an SN1 reaction depend on the solvent used?

Why is it that the extent of racemisation is greater in an $S_N 1$ reaction caried out using a polar protic solvent but the racemisation is not as extensive if an aprotic solvent is used although the ...
3
votes
1answer
2k views

Is the activation barrier of a reaction related to the free energy or heat of formation of its reactants?

The energy barrier for activation appears in the derivation of a bimolecular reaction through collision or transition state theory, but it seems that from looking at diagram such as this one it seems ...
0
votes
2answers
986 views

How to transform a tertiary alcohol to a carboxyl?

I am trying to transform a lipid with a tertiary alcohol into a carboxylic acid. More specifically, I want to convert to diplopterol (see below) into something homologous to cholesteryl hemisuccinate ...
2
votes
2answers
1k views

Time to effervescent an effervescent tablet

Say I have an effervescent tablet and I put in water. I thought that if I break the tablet in two halves it would dissolve quicker than with the whole table (without breaking), but it actually takes ...
6
votes
2answers
855 views

Bonding and Antibonding

So I understand, electrons exist in orbitals, mainly s, p, d, f and that when they bond with one another it will form sigma and pi bonds and that whether it bonds in a certain orientation a molecular ...
4
votes
1answer
580 views

Why do aqueous solutions always have to be electrically neutral?

I was reviewing some analytical chemistry and stumbled upon a section that explained the imperfection of using a salt bridge. It said that the using dissimilar ions is a problem because in, for ...
3
votes
1answer
2k views

Electrolysis: Water to Hydrogen gas?

I recently conducted an experiment where I electrolyzed a solution of sodium chloride. I was using a copper coin as the anode, and I observed a pale blue precipitate in the cup when I was done with ...
3
votes
1answer
168 views

Are there any free electrons in metal vapor?

Metals contain free moving electrons, in both the solid and liquid state. Does this happen when it is in vapor form?
1
vote
1answer
206 views

synthesizable functional groups [closed]

I was told in this question: https://chemistry.stackexchange.com/questions/4789/synthesizability-and-energy-minimization-of-a-structure/4791#4791 to [Count the] "number of accessible functional ...
2
votes
2answers
93 views

How do you determine which entity gains or loses an H+ in an equation?

$$\ce{HCO3- (aq) + H2O(l) <=> H2CO3(aq) +OH- (aq)}$$ I do not understand why this makes an Arrhenius base and why it doesn't form: $$\ce{HCO3- (aq) + H2O(l) <=> CO3^2- (aq) +H3O+ (aq)}$$ ...
4
votes
1answer
2k views

I have to write a Python program relating with molecular weight. Any insight?

Write a program that determines the molecular weight of a chemical compound based on the number of hydrogen, carbon, and oxygen atoms in the compound. You should use the following atomic weights: \...
3
votes
2answers
1k views

Approximation of electron density of a small molecule

Starting point for Quantum Theory of Atoms in Molecules (AIM) is the electron density $\rho(r)$. It could be determined experimentally (X-ray diffractions). I want to know how can we estimate them ab ...
3
votes
1answer
1k views

What is the standard heat of formation of the nitrate ion, based on the standard enthalpy of formation of silver nitrate?

Given the standard enthalpy of formation of $\ce{AgNO3(aq)} = \pu{-99 kJ/mol}$ and the standard enthalpy of formation of $\ce{Ag+(aq)} = \pu{+105 kJ/mol}$, what's the standard heat of formation of $\...
7
votes
1answer
521 views

How is this an autocatalytic reaction?

I'm probably missing a simple component of this reaction, but for some reason I not seeing it. These are two steps that compose a radical process of the Briggs-Rauscher reaction (that are ...
3
votes
2answers
17k views

Source of the no. of isomers in alkanes, and other organic molecules [closed]

I would like to ask if there is a source where I can find all the isomers for the alkanes, or other organic molecules. With other words, a list where each molecule of that group is stated in ascending ...
14
votes
1answer
12k views

If electrolysis splits water, why does only either hydrogen or oxygen (but not both) bubble up on one pole?

If electrolysis splits water, then that means that $\ce{H2O}$ is split into $\ce{H}$ and $\ce{OH}$ or $\ce{O}$. How come that if a water molecule is split at e.g. the negative pole (anode), only the ...
1
vote
1answer
281 views

What does the signals in a XPS spectrum mean?

I was trying to figure out the different peaks in a XPS spectrum for Molybdenum, but I could not understand them. About XPS, I know that this technique is based on the binding energy of the electrons ...
4
votes
1answer
41k views

How many electrons are transferred in this redox reaction?

I have the following reaction: $$\ce{CH_4 (g) + 2O_2 (g) \rightarrow CO_2 (g) + 2H_2 O(l)}$$ How do I determine how many electrons are transferred in this reaction? More specifically, I need to know ...
23
votes
2answers
69k views

Melting and boiling points of transition elements

The melting and boiling points of transition elements increases from scandium ($1530~\mathrm{^\circ C}$) to vanadium ($1917~\mathrm{^\circ C}$). They increase because as we go across the group, we ...
2
votes
1answer
1k views

Which d-orbital configurations form an octahedral complex?

With reference to crystal field splitting in octahedral complexes, my textbook shows the following table of distribution of $d$-orbital electrons in octahedral complexes, based on the energy ...
54
votes
8answers
35k views

Why do compounds like SF6 and SF4 exist but SH6 and SH4 don't?

Both $\ce{SF6}$ and $\ce{SH6}$ and $\ce{SF4}$ and $\ce{SH4}$ have the same central atom and the same hybridization, but my teacher specifically mentioned that $\ce{SH6}$ and $\ce{SH4}$ don't exist. I'...
3
votes
1answer
6k views

Diamagnetism in sulfur

Sulfur is a diamagnetic element, meaning that it has no unpaired electrons. But its electronic configuration for valence shell is just like oxygen because they are in the same group i.e ns2, np4. My ...
7
votes
3answers
15k views

What is meant by "no d-orbital"?

Sulfur and oxygen belong to the same group. Sulfur has a vacant d-orbital while oxygen has no vacant d-orbital. What does having "no d-orbital" mean? Orbitals are just the spaces around the atom. ...
4
votes
1answer
2k views

How is hydration free energy of a solute measured experimentally?

I am reading a paper (Shirts, M. R.; and Pitera, J. W. and Swope, W. C. and Pande, V. S. J. Chem. Phys. 2003, 119, 5740-5761). Near the beginning of the paper (page 5745), the authors state: ...
2
votes
2answers
536 views

How many of different types of chemical species are in a certain volume of aqueous solution of an acid

The acid in question has $\mathrm{p}K_\mathrm{a}$ about 1.29. Density of 98% w/w solution is $d=\pu{1.323 g/cm^3}$. I would like to find the number of undissociated acid molecules ($\ce{HX}$), water ...
6
votes
1answer
6k views

Why do sodium halides react so differently with sulfuric acid?

Why do sodium halides react so differently with sulfuric acid? \begin{align} \ce{NaF + H2SO4 &-> NaHSO4 + HF} \tag{1a}\label{NaF}\\ \ce{NaCl + H2SO4 &-> NaHSO4 + HCl} \tag{...
11
votes
1answer
400 views

Books for a very advanced 3rd grader (elementary school) [duplicate]

My daughter is a 3rd grader, but she reads at 8th grade level, and she is 2 grade levels ahead in math. She reads everything she gets her hands on. She took some chemistry activities, and she loved ...
1
vote
1answer
579 views

Why do we need to incubate this system for 18 hours at 60 degrees Celsius?

I am conducting a bio-chemistry related experiment and I have been unable to understand a step which is commonly performed. The procedure that is confusing me is outlined in the supporting information,...
0
votes
1answer
6k views

Why is there a charge on COOH⁻¹?

The dissociation of formic acid ($\ce{HCOOH}$) is: $$ \ce{HCOOH -> H+ + COOH-} $$ Why is there a charge on $\ce{COOH^{-1}}$ though? Is it achieved through: $$1\times(\ce{C^{4+}}) + 2\times(\ce{O^...
5
votes
1answer
3k views

Removing wine stains from a decanter

I have a decanter which I use fairly often to pour out wines. I typically rinse it with hot water after the last wine has come out, but I cannot prevent it from forming 'residual' wine stains over ...
8
votes
3answers
11k views

Chemically removing rust without leaving any unwanted residues

I have this iron pan that got rusty from not being properly dried. Scrubbing it I was able to get rid of most of the rust, but there's still some I just can't remove. I thought I could chemically ...
2
votes
0answers
356 views

Glassware Test Instruments CAD blocks library

I am designing a fairly simple distillation for dichloromethane. Being an engineer I feel more comfortable working with precise dimensions of both the separate glass vessels (condensers, evaporators, ...
2
votes
2answers
14k views

When is it okay to use $Q=mc\Delta T$, is this equation only for calorimetry questions?

When is it okay to use $Q=mc\Delta T$, is the equation only for calorimetry questions? When a question talks about heat how do I know if i'm measuring $\Delta H$ or Q?
7
votes
2answers
8k views

In aminobenzoic acid, do we have three different pKa's?

In para-aminobenzoic acid, how can I know whether the amino group loses a proton or not when $\mathrm{pH}$ exceeds $8.5$? I have only found two values for $\mathrm{p}K_\mathrm{a}$ but I never found ...
9
votes
2answers
515 views

Did Mendeleev predict the existence of neutrinos?

According to this Wikipedia page, Mendeleev originally believed that the inert gases belonged in Group 0 (to the left of the alkali metals). Thus, helium would be placed in the second period to the ...
2
votes
1answer
756 views

Bonding in a bridged metal carbonyl

Can someone please explain the bonding in a bridged metal carbonyl (like diiron nonacarbonyl)? I cannot understand what kind of bonds (sigma/pi) exist between the bridging carbonyls and the metals. ...
1
vote
1answer
1k views

Confusion about the charge of electrons while orbiting through bohr's energy shells

I came across the following part in my text book. Bohr's atomic theory explained the stability of an atom by the idea of energy shells. He said that while orbiting the nucleus through a particular ...
7
votes
1answer
2k views

Can there exist any element which has an 8th principle shell?

I am a high school student . While studying the atomic structure a question raised in my mind. We know that an atom can have the highest limit of 7 bohr energy shells or principle energy shells ; K,L,...
4
votes
2answers
8k views

(How) Does ICP-OES determine the quantity of detected elements, or just their occurance in the sample?

ICP-OES is a very common analytical method (Wikipedia page here), and I have heard a number of times (from chemists, too) that it is used for quantitative analysis. However, from the description of ...
1
vote
2answers
143 views

What analytical methods are used to quantify C, O, N, and H in a sample?

A very common analytical method for detection of more than 70 elements is ICP-OES (Wikipedia page). But apparently, it's not suited for some substances (cited from this paper, section 6.2, page 12): ...
1
vote
1answer
8k views

Result of glucose with acetic anhydride and pyridine?

What is the result when glucose is mixed with excess acetic anhydride and excess pyridine?
2
votes
1answer
85 views

What compounds do Nor1 and Nor2 citalopram refer to?

In Goodman and Gilman's The Pharmacological Basis of Therapeutics 12th Edition pg. 406, two drugs, nor1-citalopram and nor2-citalopram are referred to but I have no idea what they are. Could somebody ...
1
vote
1answer
517 views

How to write down the composition of eluent mixtures for TLC

I obtained some Rf values via TLC by adding two or three drops methanolic triethylamine to an eluent mixture of let's say DCM/MeOH = 9:1. I couldn't find an example of how a mixture like that is ...
2
votes
1answer
5k views

Gas Electrode Working

How does a SHE electrode work? Does the $H_2$ gas get absorbed on the platinum electrode? How is it reduced? How are electrons transferred from the adsorbed gas to the solution? How is $H^+$ ...
1
vote
1answer
686 views

Electrochemical Cell

Now in an electrochemical cell , we make use of the fact that whenever there is a potential drop , electrons will flow from lower to higher potential as for a potential drop , there must be an ...
6
votes
2answers
506 views

Can iproniazid be prepared by reacting isoniazid with 2-chloropropane?

I'm asking as I fear that the 2-chloropropane might react with the pyridine ring to form k-isopropylpridine-4-carbohydrazidine where k=2,3,5. Or that no reaction will take place. Figure 1: Isoniazid ...

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