Questions tagged [acid-base]
This tag should be applied to questions concerning acid and base reactions. An acid is capable of donating a hydron/ proton (Brønsted acid) or capable of forming a covalent bond with an electron pair (Lewis acid). A base on the other hand is a chemical species/ molecular entity having an available pair of electrons capable of forming a covalent bond with a hydron/ proton (Brønsted base) or with the vacant orbital of some other species (Lewis base).
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Is there a reliable chemical theory that predicts pKa based on structure?
Obviously, there are general stability arguments that can be made to estimate relative pKas, such as evaluating the stability of the conjugate base of an acid, or thinking about how polarized the bond ...
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Order of Basicity of Nitrogen Trihalides
I was asked to arrange nitrogen tri-halides in order of increasing basicity. On looking up the answer online, it turned out to be the following: $\ce{NF3}$ < $\ce{NCl3}$ < $\ce{NBr3}$ < $\ce{...
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Why is o-fluorophenol a stronger acid than p-fluorophenol?
The $\mathrm{p}K_\mathrm{a}$ value of o-fluorophenol is $8.7$, while that of the p-fluorophenol is $9.9$. It's obvious that the inductive effect is more dominant at ortho-position, which results in a ...
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Does phosphoric acid remove stainless steel electropolished layer?
Electropolished stainless steel has a high corrosion resistance due to the oxide film that is created during electropolishing. The film mainly consist of chromium(III) oxide.
Phosphoric acid is ...
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Why is carbon monoxide non-Brönsted-basic in aqueous solution when it has a lone pair on carbon?
Carbon monoxide is not protonatable in aqueous solution; a quick Google search even leads to a paper that talks about using carborane acids, i.e. extreme superacids, to protonate the molecule.
However,...
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pKa of different sites of butanone
From what I can tell, deprotonation of the central hydrogen leads to the more thermodynamically stable product (most substituted double bond. i.e. most stabilization by hyperconjugation). Therefore, ...
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Yellow precipitate in SnCl2 solution
I have a few small bottles of 0.5M $\ce{SnCl2}$ solution, however solution was prepared about 4 months ago, and there is a yellow precipitate on the bottom of each bottle. Working hypothesis is that ...
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Ligand strength - Coulombic effect and/or Electronegativities?
According to my teacher, these three Lewis bases generally decrease in strength in the following order:
Ammonia
Water
Hydroxide ion
I agree. However, he argues that their ability to act as Lewis ...
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What is the pKa of the O-17 hydronium ion?
At low concentrations of a conjugate acid/base pair in aqueous solutions, the Henderson-Hasselbalch equation gives a good approximation of the ratio of acid and base:
$$ \frac{[\ce{A-}]}{[\ce{AH}]} = ...
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How to make a thin layer of crystalline barium titanate on copper substrate?
Is it possible to create a thin $\ce{BaTiO3}$ crystal layer on a copper plate by putting the plate in a beaker, pouring in heated hydrofluoric acid that has been saturated with $\ce{BaTiO3}$ powder ...
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Comparing acidic strength of phthalic acid isomers
I'd like to compare the acidic strengths of phthalic, isophthalic and terephthalic acids. As I understand, phthalic acid is the most acidic due to steric inhibition of resonance (SIR), but as ...
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What pH value of 1M sodium crotonate solution supposed to be?
I need to prepare the $\pu{1M}$ solution of sodium crotonate, however, I don't have one in lab, but I do have sodium hydroxide and crotonic acid.
Thus, I calculated that for $\pu{100 mL}$ of $\pu{1M}$ ...
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What acids, solvents is lithium-6 fluoride soluble in (other than HF)?
$\ce{LiF}$ is quite insoluble in water, and I'm trying to use some water-soluble acid or solvent to dissolve $\ce{^6LiF}$ (95% enriched) in. I'm not a chemistry person, I'm a radiation detection ...
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Solubility of PbSO4
The solubility of $\ce{PbSO4(s)}$ increase with the addition of $\ce{H2SO4}.$ Why?
I don't quite understand this. When dissolving $\ce{PbSO4(s)}$ we get the equilibrium equation:
$$\ce{PbSO4(s) <=...
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Why does my rainwater turn yellow if I increase the pH to 7?
My rainwater is colourless when collected, but if I add a small amount of sodium hydroxide to increase the pH to about 7, after a few days it goes yellow.
The colour change happens more quickly if I ...
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Which is the stronger base?
I would like to know which of the two is the stronger base, tri-(n-butyl)amine or tri-(tert-butyl)amine?
I feel that the one with tert-butyl would be stronger as the inductive effect of tert-butyl ...
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How does a 5th hydrogen bind to carbon atom in CH5[+]?
Can we bind a fifth hydrogen to a carbon atom if carbon is not in excited state?
We have a big discussion in class and cannot clearly answer the question. If carbon atom excites an electron from $2\...
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Trouble understanding Bradford Assay
From what I understand, the Bradford reagent contains Coomassie Brilliant Blue in an acidic solution so both of the (sulfonic acid groups? I'm not sure if this is the correct name- I can't seem to ...
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Is there a way to force C-protonation of an enolate?
In another question, I mentioned that O-protonation of an enolate followed by tautomerization may lead to increased amounts of the thermodynamic product over the kinetic product (when those are ...
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Is phosphorus trichloride really a stronger Lewis acid than antimony pentafluoride?
The following was a question from the ETS Chem GRE guide and apparently this was an actual question on an exam a few decades ago. Unfortunately, no explanation for the answer was given, and I couldn't ...
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One half of a nail is exposed to vinegar. Un-exposed half develops a brown film. What is it?
I have recently done an experiment for my chemistry EEI (Year 12) where we are testing what factors effect the rate of corrosion. I used vinegar (acetic acid) as one of the acids and Hydrochloric acid ...
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What does "acidic" mean in an article on hydrogen boride nanosheets?
From Rojas et al. [1] (emphasis mine):
On the other hand, we found that proton exchange with HB occurs in water with the estimated $\mathrm{p}K_\mathrm{a}$ of $3.5\pm 0.2,$ even after reactive sites ...
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Why do vessels get a better shine when tea-leaves are soaked overnight in it before washing?
The other day I dumped consumed tea leaves into a brass utensil because I needed the tea-pan urgently. The vessel with the tea leaves didn't get around for cleaning until the next day. Ergo, the tea ...
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The role of 2-nitrophenol in tin etchant (aqueous mixture of 2-nitrophenol and NaOH)
Aqueous mixture of 2-nitrophenol and NaOH is a time-honored etchant that dissolves tin-rich alloy and retain the intermetallic compounds from the tin. I wonder the role of 2-nitrophenol in the etching ...
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What are the applications of tetraxenonogold(II)?
I recently stumbled upon a pretty interesting chemical: tetraxenonogold(II) $\ce{AuXe4^2+}.$ Basically, an atom of gold with four xenons around. It is a product of a superacid reaction and it is ...
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Is there an adhesive that is not dissolved by acetone?
I am trying to glue glass sheets together to make a sealed 13" x 13" x 13" box. Inside this box there would be acetone gas used to melt 3D printed parts to make them more durable. Acetone will remove ...
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How can should one separate and purify benzophenone from salicylic acid?
I am working with two solids and I know that they are benzophenone (s)(ketone) and salicylic acid (s) (carboxylic acid). I am curious to know what is/are the best method of extraction and ...
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Why is the experimental pH of vinegar (acetic acid) so much higher than expected?
I bought some sodium hydroxide on Amazon and went about titrating solutions I make with it.
As I'm an amateur chemist at home, I have limited tools. A pad of paper, some 5% acetic acid vinegar, and ...
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acid strength: Periodic trends vs delocalisation, which one is more important
In 1st year chemistry questions, the concept of acid strength is often introduced to students including the 3 factors that provide a heuristic explanation for most of the common acids and conjugate ...
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Basicity af N containing aromatic species
Hello friends, I got struck in this interesting question on basicity. I am able to get different answers applying different methods.
In general, for these compounds we have to see the lone pair ...
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Naming convention for buffer solutions/systems
Is there an official naming convention to follow for buffer solutions/systems? I've noticed that the name of the buffer usually just follows the name of the salt (ex. sodium acetate buffer), but what ...
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Effect of H-bonding on o-nitrobenzoic acid
My argument here is regarding the acidity of o-nitrobenzoic acid being greater than p,m-nitrobenzoic acid. In o-nitrobenzoic acid, there is an intramolecular hydrogen bond which makes the bond ...
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Titanium in HF vs HCl
So we tried the reaction between Titanium metal with hydrochloric acid and hydrofluoric acid at a similar concentration. While boiling temperatures and constant heat over a long period of time are ...
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Collective term for acid/base; hydronium/hydroxide
When writing about acids and bases it would seem very natural for me to abstract the set of both acids and bases and have a single noun for them, instead of cumbersomly listing them both each time. ...
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How can I find pKa from a titration curve?
I am fully aware that the pKa is the pH at half the equivalence point, but are there some programs or methods I could use to accurately estimate the pKa without manually drawing lines on the graph?
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Hydrolyse Phosphonate diester to free phosphonic acid under relatively mild conditions?
I want to hydrolyse a phosphonic acid diethylester to the corresponding free phosphonic acid. In the literature, it is described, that usually strongly basic or acidic conditions are utilized to ...
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Measuring [A-]/[HA-] with Buffer and Indicator
I'm very confused on how to calculate the [A-]/[HA] value, given the fact that my dilution series uses buffers at various pH values with the same indicator (supplied at the same concentration to each ...
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Why is a protonated carboxylic acid less acidic than a protonated ester?
To my understanding, both have analogous resonance structures except that the ester has on -OR and the carboxylic acid has an -OH. Why is a positive charge on C-O-R more stable than on C-O-H?
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Is hydrochloric acid or sulfuric acid more corrosive to titanium?
Which acid is more corrosive to titanium at 20 to 30 °C and similar concentrations: hydrochloric acid $\ce{HCl}$ or sulfuric acid $\ce{H2SO4}$?
I found some info on AZoMaterials — Titanium - Corrosion ...
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How to establish trend of carboxylic acid acidity in the presence of certain substituents?
I encountered a question in my textbook which asked the following:
At first, i thought that i can approach it in the same way i sort the effect of EDG and EWG on the acidity of phenols, that is, ...
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Gibbs free energy of mixing in a control volume
I'm trying to model the amount of energy lost due to mixing of a $\mathrm{HCl}$ solution using the Gibbs free energy of mixing. However, I really like a second opinion on the model and the results, ...
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Does amide ion prefers to act as a base than a nucleophile?
In this question, I think that amide ion, being a good nucleophile should attack on the terminal carbon through $\mathrm{S_N2}$ mechanism to form compound (c), but the answer given is (b), and the ...
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What is the relation between strength of a base and the thermal stability of its salts?
In Concise Inorganic Chemistry, $5^{th}$ edition, by JD Lee, while discussing oxides and hydroxides of Group $2$ metals, it has been stated that:
The increase in basic strength is illustrated by the ...
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How measured content of Calcium Carbonate in eggshells change with the use of different acids?
I am investigating the calcium content of chicken eggshells. The only literature I can find on this consistently and solely depend on the use of HCl to conduct back titration. I conducted the ...
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Is sulphonamide group prone to undergo diazotization?
I wonder if it is not a problem that there is another $\ce{-NH2}$ group in the molecule not connected to aromatic ring and if it can get protonated and react with $\ce{HNO2}$ too, in this case the one ...
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Reactivity of unsaturated organolithium compounds
I'm particularly looking in the context of alkyl lithiums compared to vinyl-lithiums and alkynyl-lithiums.
Why is it that shifting from sp3 to sp2, and even further to sp carbanions, reduces the ...
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What are the compounds in oxygen and carbon dioxide indicator solutions that gives their color?
My brother had some leftover oxygen and carbon dioxide indicator solution for one of his take-home experiments from school, so he let me have them. I want to use them for an experiment and write out ...
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Why is N,N,2,6-tetramethylaniline less basic than N,N,2-trimethylaniline?
According to me, N,N,2,6-tetramethylaniline should be more basic than N,N,2-trimethylaniline due to more steric inhibition to resonance, but the answer is given opposite. What is the reason for that?
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Basicity comparison between pyridine amines and other compounds
In cases 1, 2, 3, the compounds will resonate, thus giving them more stability.
Firstly, I want to know whether nitrogen has a +M effect? (due to it having a lone pair of electrons?)
In case 1, ...
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How to control pH in a fermenter based on the acid produced by mircoorganism
I have got a bioreactor with an aqueous medium which produces biomass (yeast; S.cerevisiae) after inoculation.
I am observing and collecting data over the whole process via probes/etc. on different ...
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