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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 ...
sweetandtangy's user avatar
9 votes
1 answer
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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{...
NightMare's user avatar
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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 ...
whateven's user avatar
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Steric inhibition of resonance vs. hydrogen bonding

I have to compare the acidic strength of these compounds: Now, in A and B hydrogen bonding will be present which will help stabilize the negative charge of the conjugate base. However, the hydroxyl ...
xasthor's user avatar
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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 ...
Jaroslav Kotowski's user avatar
7 votes
0 answers
546 views

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 ...
Dissenter's user avatar
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6 votes
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113 views

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,...
Kanghun Kim's user avatar
6 votes
0 answers
502 views

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, ...
Adroit's user avatar
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746 views

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\...
Diana51's user avatar
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2k views

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 ...
Sleepy Hollow's user avatar
5 votes
0 answers
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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}]} = ...
Karsten's user avatar
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601 views

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 ...
TeslaBolt's user avatar
  • 156
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0 answers
185 views

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 $\pu{1M}$ ...
Araneus0390's user avatar
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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 ...
user95948's user avatar
5 votes
1 answer
452 views

Acidic strength of phenol derivatives

While comparing the strengths of o-nitrophenol and p-nitrophenol, p-nitrophenol is found to be more acidic. The reason I studied for this is $\ce{H}$-bonding in o-nitrophenol which makes the acid more ...
Rajat Sansaniwal's user avatar
5 votes
0 answers
790 views

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) <=...
Kdbmvp's user avatar
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189 views

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 ...
Shaun Ross's user avatar
5 votes
0 answers
733 views

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 ...
Tan Yong Boon's user avatar
5 votes
1 answer
11k views

Reaction between sodium bicarbonate (baking soda), isopropyl alcohol, and acetic acid (vinegar)?

I observed this reaction by playing around with vinegar and baking soda and I do not completely understand it. Everyone knows that baking soda (sodium bicarbonate) and vinegar (acetic acid) go crazy ...
Matthew's user avatar
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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 ...
Meep's user avatar
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5 votes
0 answers
153 views

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 ...
SendersReagent's user avatar
5 votes
0 answers
899 views

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 ...
coloratura's user avatar
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5 votes
1 answer
338 views

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 ...
Caitlynisdunwithyou's user avatar
4 votes
0 answers
238 views

Exchange of Fluorine to Oxygen for Fluorophosphonic acid by silylating agents or other methods?

[Warning, long post!] Dear all, I am confronted with a seemingly easy transformation. I want to remove a fluorine atom at a fluor phosphonic acid salt. The usual method to achieve this is the basic ...
raptorlane's user avatar
4 votes
0 answers
64 views

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 ...
hoggywoggy's user avatar
4 votes
0 answers
73 views

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 ...
Everyone's user avatar
  • 904
4 votes
0 answers
46 views

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 ...
5ru8ek's user avatar
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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 ...
Ereandil's user avatar
4 votes
0 answers
639 views

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 ...
daniel's user avatar
  • 41
4 votes
0 answers
470 views

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 ...
Boo's user avatar
  • 71
4 votes
0 answers
439 views

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 ...
Jonathan Allard's user avatar
4 votes
0 answers
55 views

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 ...
Secret's user avatar
  • 698
4 votes
0 answers
117 views

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 ...
Michael's user avatar
  • 49
4 votes
0 answers
338 views

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 ...
YeRyeon Seo's user avatar
4 votes
0 answers
3k views

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 ...
Justanotherchemist's user avatar
4 votes
0 answers
271 views

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. ...
caconyrn's user avatar
  • 667
4 votes
0 answers
2k views

Rust removal with phosphoric acid created more rust

I wanted to remove the rust on numerous steel parts with phosphoric acid. After removing all the grease in trichloroethylene, I put my parts into a 50 % solution of phosphoric acid ad 40 °C for 5 ...
nowox's user avatar
  • 613
4 votes
0 answers
2k views

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?
user935's user avatar
  • 41
3 votes
0 answers
25 views

Non-binding buffer at pKa of roughly 6 that dissolves in ethanol?

I'm trying to find a proper buffer for my experiment, which I'd appreciate some suggestions on. I have a solution in which I want to measure the concentration of magnesium ions using a fluorescent ...
Helena's user avatar
  • 31
3 votes
0 answers
43 views

TsOH and 5% NaHCO3 Interaction: Unexpected Dark Green Color

Here's the brief: I synthesized alkyl gallates (ethyl gallate, butyl gallate, and amyl gallate) using Fischer esterification. I used TsOH instead of concentrated H2SO4 as the catalyst. After ...
Jonathan's user avatar
  • 155
3 votes
0 answers
108 views

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 ...
raptorlane's user avatar
3 votes
0 answers
75 views

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 ...
Tyler Anderson's user avatar
3 votes
0 answers
137 views

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?
gxyzv's user avatar
  • 37
3 votes
0 answers
79 views

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 ...
Cagdas Ozgenc's user avatar
3 votes
0 answers
509 views

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, ...
Doe Pual's user avatar
  • 107
3 votes
0 answers
110 views

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, ...
Jelle Westra's user avatar
3 votes
0 answers
261 views

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 ...
user avatar
3 votes
0 answers
153 views

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 ...
Ritam_Dasgupta's user avatar
3 votes
0 answers
195 views

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 ...
Yusuf Barış Köse's user avatar
3 votes
0 answers
161 views

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 ...
Bencyklan's user avatar

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