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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questions with no upvoted or accepted answers
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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 ...
7
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0answers
485 views
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 ...
6
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45 views
Are there acid/base processes in aqueous solution that are so slow that they are kinetically controlled?
This question came up in figuring out what the fundamental differences are between redox chemistry and acid/base chemistry (if any).
In redox chemistry, strong oxidants and strong reductants can co-...
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283 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, ...
6
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0answers
2k views
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 ...
6
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1answer
598 views
Why does the open circuit voltage of a battery decrease with increase in pH of electrolyte, but the voltage across a load increase?
I tested a cell which had aluminum sulfate as its anode electrolyte (12 grams aluminum in 50 mL water and a pH of 3.2), and potassium hydroxide as the cathode electrolyte (5 grams of KOH in 200 g of ...
6
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383 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\...
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1k 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 ...
6
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496 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 ...
5
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0answers
78 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 $\pu{1M}$ ...
5
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50 views
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 ...
5
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1answer
61 views
Protons and osmotic potential
In a hypothetical enclosed membrane only permeable to water (including hydronium), where inside the pH is lower than the outside, would water move inside?
5
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60 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 ...
5
votes
1answer
819 views
Which one is the stronger Lewis base: diethyl ether or tetrahydrofuran?
I am trying to understand Lewis bases (bear with me, I am a physicist). I was asking myself how diethyl ether and tetrahydrofuran compare with respect to their properties as solvents in electrophilic ...
5
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607 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 ...
5
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3answers
8k views
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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0answers
109 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 ...
5
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0answers
706 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 ...
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0answers
103 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 ...
4
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0answers
127 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 ...
4
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0answers
58 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 ...
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0answers
39 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 ...
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0answers
331 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) <=...
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0answers
89 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 ...
4
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0answers
101 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 ...
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0answers
2k views
Can ethylene glycol enhance the acidity of orthoboric acid?
My textbook says:
Boric acid is a weak monobasic acid but on addition of certain organic polyhydroxy compounds, such as mannitol, glycerol, dextrose or invert sugar, it is transformed into a ...
4
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0answers
82 views
What metal is used to back this mirror?
My father is attempting to remove the mirror from a piece of glass. We stripped the black paint from the back and exposed the shiny surface with acetone. In the past he has been able to remove ...
4
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0answers
82 views
Can someone help me finish this reaction?
This question revolves around sodium percarbonate (https://en.m.wikipedia.org/wiki/Sodium_percarbonate) and its reaction with sulfuric acid.
I didn't find anything, so I tried assembling it myself.
...
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0answers
155 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. ...
4
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1answer
2k 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 ...
4
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1answer
177 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 ...
3
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0answers
24 views
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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0answers
169 views
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?
3
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1answer
60 views
Acidity of thiamine - how comes hydroxide anion with pK about 15 ionizes thiamine with pK about 18?
Textbooks say removing proton from thiamine's C atom will produce a resonance stabilized carbanion which is hence bioactive. That's OK, but how comes that 1) we abstract the acidic proton with the OH ...
3
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27 views
Acidity comparison on R-PO3H2
Question
Compare the acidity $(K_\mathrm{a1})$ of the following three acids:
$\ce{H3PO4},$ $\ce{Ph-PO(OH)2}$ and $\ce{H3C-PO(OH)2}.$
Thoughts
These three acids are of type $\ce{R-PO3H2},$ where ...
3
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0answers
298 views
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, ...
3
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0answers
82 views
Common ion effect
Let $\ce{HA}$ ($x$ molar) be a strong electrolyte and $\ce{HB}$ ($c$ molar) — weak electrolyte. As $\ce{HA}$ is strong electrolyte, it dissociates completely:
$$
\begin{array}{lcc}
\ce{&HA &-&...
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198 views
Why AlCl3 more acidic than FeBr3?
In compounds with lone pairs or with charge it is easy to predict acidity of compounds but how to describe acidic nature of such ($\ce{FeBr3}$, $\ce{AlCl3}$) transition element compounds ?
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1k views
Acidity comparison of charged group 16 hydrides
March's Organic Chemistry (7th ed - page 337 under "Periodic Table Correlations" in chapter "Acids and Bases") states that:
$\ce{H3O+ > H3S+ > H3Se+}$ is the acidity order of these charged ...
3
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0answers
629 views
Why does the proton transfer from the oxygen to the nitrogen atom in imine formation not occur through an intramolecular process?
In my book Organic Chemistry by David Klein, 2nd edition, the book shows that the oxygen atom first takes a proton from an acid, then, the conjugate base of the acid takes a proton from the nitrogen ...
3
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0answers
93 views
Is DNA a base inside the cell?
DNA is deoxyribonucleic acid because it has phosphate groups in every one of it's nucleotides.
However, in aqueous solutions protons will ionize, leaving phosphates alone as negative groups, i.e., ...
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0answers
370 views
Enthalpy change of chromate-dichromate reaction
I am a uni study doing chemistry. I have taken a little bit in highschool before, but not in a while.
In a (nonassessed) practical, we have to predict how heating a chromate/dichromate solution:
$$\...
3
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0answers
141 views
Constructing a reactivity series, magnesium more reactive than sodium?
I reacted about $0.25 \,\mathrm{g}$ of magnesium, sodium and lithium in $20 \,\mathrm{ml}$ of $2 \,\mathrm{M} \,\ce{HCl}$ at room temperature. This was all done in a $100 \,\mathrm{mL}$ beaker.
I ...
3
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0answers
130 views
Material that acts as a “sponge” for sulfuric acid?
I would like help with a materials problem I am looking into that pertains to a product I would like to develop.
What I seek is some kind of substrate that acts like blotter paper does. Ideally, the ...
3
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0answers
49 views
Trouble understanding Bradford Assay
From what I understand, the Bradford reagent contains Coomassie Brilliant Blue in an acidic solution so both of the (sulfonic acid groups? I'm not sure if this is the correct name- I can't seem to ...
3
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0answers
2k views
Hard and Soft Acid and Bases in terms of HOMO and LUMO
It has been given in a book and on Wikipedia that:
hard bases have highest-occupied molecular orbitals (HOMO) of low energy, and hard acids have lowest-unoccupied molecular orbitals (LUMO) of high ...
3
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0answers
108 views
Acid-Base Conjugate Pairs with multiple Products
Identify the acid-base conjugate pairs in the following reactions:
$$\ce{H_2SO_4 + HNO_3 <=> HSO_4^- + NO_2^+ + H_2O}$$
The obvious acid base conjugate pair is $\ce{H_2SO4}$ and $\ce{HSO_4^-}$...
3
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0answers
2k views
Lassaigne's test for sulfur
The sodium fusion extract is acidified with acetic acid and lead acetate is added to it. A black precipitate of lead sulphide indicates the presence of sulphur.
What is the need for acidification of ...
3
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0answers
472 views
Why would the effect of fluoride ions Protecting egg shells from acid erosion vary with different acids?
I did an experiment reacting egg shells and acid. The egg shells were soaked in varying concentrations of fluoride and it is seen the rate of reaction between egg shells and acid decreases with higher ...
3
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0answers
193 views
Relative etch rates of nitric acid on metals and oxides
I am trying to either find or calculate the etch rate of nitric acid ($\ce{HNO3}$) for various different metals and oxides. The ones I am interested in are titanium ($\ce{Ti}$), zirconium ($\ce{Zr}$), ...
