We’re rewarding the question askers & reputations are being recalculated! Read more.

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).

Filter by
Sorted by
Tagged with
12
votes
1answer
12k views

Basicity Alteration Due To Ortho Effect In Methoxy Aniline System

I wanted to ask something more in reference to this question Ortho-effect in substituted aromatic acids and bases Suppose instead of toluidine, 2-methoxyaniline and 3-methoxyaniline are present. Now ...
12
votes
1answer
7k views

Why would sulfuric acid turn gray/black?

About 2 years ago I purchased 2 liters of 98% concentrated sulfuric acid. It's in a standard poly bottle with leakproof lids, and originally was clear. Recently I noticed the acids have turned a dark ...
12
votes
1answer
1k views

How to analyze a acid and salt mixture using titrimetry?

Given a mixture of $\ce{HCl}$ and $\ce{MCl3}$ and the following dissociation constants for $\ce{M(OH)3}$, how can the concentrations of $\ce{HCl}$ and $\ce{MCl3}$ be determined separately by titrating ...
12
votes
2answers
2k views

Why is trimethylsilanol a stronger acid than tert-butanol?

The Wikipedia article about trimethylsilanol says the following: Trimethylsilanol is a weak acid with a $\mathrm{p}K_\mathrm{a}$ value of 11. The acidity is comparable to that of orthosilicic acid, ...
12
votes
1answer
291 views

What is the structure of trifluoromethanesulfonic acid in the gas phase?

During an interesting discussion in our group’s seminar, the question arose what actually causes trifluoroacetic acid to be a much better nucleophile than trifluoromethanesulfonic acid. Part of the ...
12
votes
2answers
471 views

Why quaternary nitrogen but not tertiary oxygen?

Why do quaternary ammonium ions with a partially positive nitrogen form fairly readily and are often stable but tertiary oxygens, apparently called oxonium ions, are more rare/less stable? The trend ...
12
votes
1answer
383 views

Single electron reduction of ketone by Na or Zn

Whenever we add Na or Zn metal to a ketone, why does the electron prefer to attack the carbonyl bond and form a radical, instead of removing the acidic hydrogen and forming an enolate and $\ce{H2}$ ...
12
votes
2answers
6k views

How to calculate partition coefficients?

Below is a transcript of this doubtful question: A weak monobasic organic acid $\ce{HA}$ is soluble in both water and $\ce{CHCl3}$. $\pu{500.0 cm3}$ of a solution of $\ce{HA}$ in $\ce{CHCl3}$, ...
11
votes
3answers
3k views

Is an acid a salt or not?

In our office, we discussed today what the exact definition of a salt is and whether an acid itself can be classified as a salt. Our first problem was that we couldn't get a definitive definition for ...
11
votes
4answers
61k views

Is sulfuric acid or hydrochloric acid stronger?

Of my belief, sulfuric acid might be a little stronger than hydrochloric acid. Because even though they both are strong acids, one mole of sulfuric acid produces two times as much $\ce{H+}$ as one ...
11
votes
2answers
487 views

How does strength of boric acid solution increase in presence of salicylic acid?

A while ago, I read that salicylic acid can make boric acid solution strongly acidic when it's added to it. To my knowledge, I know that boric acid becomes a strong acid in presence of cis-diols (...
11
votes
2answers
3k views

Do acids really donate a proton?

Will acids really donate a proton? In an atom, the proton is inside the nucleus and I don't think a proton will go all the way out of atom dodging all electrons and enter into the nucleus of the base. ...
11
votes
1answer
16k views

Is an ester or a ketone more acidic?

Two organic chemistry textbooks I've read (by Bruice and by Tandon) say: Esters are more acidic than ketones, because the resonance between the two oxygen atoms gives less opportunity for the ...
11
votes
1answer
39k views

How do I calculate the isoelectric point of amino acids with more than two pKa's?

For most amino acids, the $\mathrm{pI}$ is simply the mean of the amino and carboxyl $\mathrm pK_\mathrm a$'s. However, for tyrosine and cysteine, which have more than one $\mathrm pK_\mathrm a$ value,...
11
votes
4answers
52k views

Shouldn't the pH at the equivalence point always be 7?

I learned in class that the equivalence point in an acid-base titration is reached when the solution contains an equal amount of substance of $\ce{OH-}$ and $\ce{H+}$ ions. However, in a weak acid and ...
11
votes
1answer
768 views

Why are indicators used only in the form of dilute solutions?

Why are indicators used only in the form of dilute solutions? I get that indicators are a form of weak acids themselves, and the extent of their dissociation varies with the pH of the solution they ...
11
votes
3answers
15k views

Why are acetals stable to bases and nucleophiles?

Why are acetals stable to bases and nucleophiles? Could it be due to electronic effects? Lone pairs on the two oxygen atoms create an unfavorable environment for the approaching nucleophiles and ...
11
votes
1answer
13k views

Why does HNO3 not give off H2 when reacting with Cu?

A dilute solution of which acid is most likely to produce a reduction product other than $\ce{H_{2}}$ when it reacts with a metal? (A) $\ce{HF}$ (B) $\ce{HCl}$ (C) $\ce{HNO3} $ ...
11
votes
2answers
13k views

Do hydrogen halides (HX) form strong or weak acids?

I know that when dissolved in water, hydrogen halides ($\ce{H-X}$), become acids. I know that $\ce{HF}$ forms a weak acid, but can it be generalized that all $\ce{HX}$ acids do so?
11
votes
2answers
144k views

What are the products of the dissociation of sodium bicarbonate in water? What is the relative pH of the solution?

I had a recent question on a test that asked what the products would be if sodium hydrogen carbonate were dissolved in water. I had a few candidate answers $\displaystyle\ce{NaHCO3 -> Na+ + HCO3-}$...
11
votes
1answer
28k views

Condition For NaHCO3 to react to form CO2 with organic acids

My professor told us the following: $\ce{NaHCO3}$ will react to evolve $\ce{CO2}$ whenever the acidic nature of the reactant exceeds the acidic nature of benzoic acid. I want to know why this ...
11
votes
1answer
8k views

Does unsubstituted benzoic acid not show resonance due to steric effects?

My book says that benzoic acid does not show resonance as the carboxylate anion and the benzene ring are not in the same plane due to steric effects. But there aren't any large groups in the ortho ...
11
votes
1answer
651 views

What is the most acidic proton of 2-methylcyclopent-2-en-1-one?

In an acid-base reaction of $\ce{HO-}$ with 2-methylcyclopent-2-en-1-one, which is the most acidic proton? I had assumed it was one of them coming off the carbon 5 according to IUPAC numbering (&#...
11
votes
1answer
6k views

Why is ammonia so much more basic than water?

The only reason I can think of is that the lone pairs in the oxygen in water are in lower energy orbital relative to the nitrogen in ammonia due to increased effective nuclear charge in oxygen. ...
11
votes
2answers
2k views

Acidity of hydrochloric acid in acetic acid

A question asked to find the $\mathrm pK_\mathrm a$ of $\ce{HCl}$ in acetic acid. The equation of $\ce{HCl}$ disassociating in water is: $$\ce{HCl + CH3COOH \leftrightharpoons CH3COOH2+ + Cl-}$$ I ...
11
votes
1answer
2k views

Why can't phosphorus trifluoride be used as a Lewis acid catalyst in electrophilic substitution of benzene?

Which of the following cannot be used as Lewis acid in the electrophilic substitution of benzene? $\ce{BF3}$ $\ce{SbCl3}$ $\ce{FeCl3}$ $\ce{PF3}$ My Attempt: $\ce{BF3}$ and $\ce{...
11
votes
2answers
9k views

Which is more basic, hydrazine or ammonia?

Which of the following will be more basic, hydrazine $\ce{H2N-NH2}$ or ammonia $\ce{NH3}$? My chemistry teacher said that $\ce{NH3}$ is more basic since after giving $\ce{H+}$ to hydrazine results in ...
11
votes
1answer
3k views

exchanging H2O in buffer for D2O - pH vs pD?

I have TBS pH 7.4 buffer that I am exchanging all the water out for $\ce{D2O}$. How do I find out what the pD is after all the water is gone? I understand that pH meters don't work for deuterium, and ...
11
votes
1answer
117 views

How sure can we be about the structure of purine?

While answering the question Basicities of nitrogen atoms in purine, I noticed, that there might be a rapid interchange of the hydrogen bonded to the nitrogen atoms. I have found a crystal structure ...
10
votes
2answers
4k views

How can I identify whether a substance is KOH or NaOH?

I've bought $\ce{NaOH}$ or $\ce{KOH}$ (I don't remember which one!) for my electrolyzer and I've tested it. Now I want to improve its performance and I was searching for a better electrolyte when I ...
10
votes
3answers
641 views

Why can the lone pair not align with the phenyl moiety in 2,6-xylidine?

I am told that for 2,6-xylidine (2,6-dimethylaniline), the amino group cannot line up in such a way that its p-orbital is parallel with respect to the p-orbitals of the carbons in the ring. I've ...
10
votes
3answers
7k views

How can the equilibrium shift, while Kc remains constant?

Consider the following reversible reaction. $$\ce{Cr2O7^2-(aq) + H2O(l) <=> 2 CrO4^2-(aq) + 2 H+(aq)}$$ What will happen to the position of equilibrium and the value of $K_c$ when more ...
10
votes
3answers
972 views

Where is the acid in DNA/RNA?

It is well known that the A in both DNA and RNA stands for acid, but where is the acid in chemical formula for the compound, and it is classified so based on what acid-base theory? Like Arrhenius, ...
10
votes
2answers
6k views

How can bromine water be called a solution?

Bromine water is a reagent which is used to test for unsaturation in organic compound. It is $2.8~\%$ bromine in water according to Wikipedia. But how is it made? This link describes the procedure ...
10
votes
2answers
3k views

Is ciprofloxacin acidic or basic?

I would expect an aqueous solution of ciprofloxacin to be basic for the following reasons: The carboxyl group has pKa = 6.09 and the secondary amino group has pKa = 8.74. Because 8.74 is further from ...
10
votes
1answer
4k views

How does the HCl-KCl Buffer work?

I have just been studying the $\ce{HCl}$-$\ce{KCl}$ 'buffer', but there are still quite a few things I am uncertain about. I would appreciate any help in clearing up some questions I have. What I ...
10
votes
2answers
4k views

More acidic - protonated carbonyl or protonated hydroxyl?

Consider two acetic acid derivatives, one with a protonated carbonyl oxygen and one with a protonated hydroxyl oxygen. An argument for the one with the protonated hydroxyl oxygen being more acidic ...
10
votes
1answer
274 views

Esterfication of 2,2,2-triphenylethanoic acid

Explain the formation of (1,1,1-triphenylmethyl)methyl ether when a solution of 2,2,2-triphenylethanoic acid in concentrated sulfuric acid is poured in methanol. I cannot figure out where is one ...
10
votes
1answer
5k views

Why is picric acid more acidic than carbonic acid?

I just had a question in a test asking to compare the relative acidity of picric acid (TNP) and carbonic acid, $\ce{H2CO3}$ (not phenol). It turns out that TNP is more acidic. I have no idea why? Is ...
10
votes
1answer
8k views

Why does hydrogen bonding in salicylic acid make it more acidic?

When salicylic acid deprotonates (losing the proton from the carboxyl group) it forms a hydrogen bond with between the oxygen in the carboxylate anion and the hydrogen in the alcohol group. However, ...
10
votes
1answer
271 views

Protonating/basic site and Brønsted basicity orders of beta, gamma, and delta lactams

Consider the three cyclic amides: $\beta$-lactam $\gamma$-lactam $\delta$-lactam My question What is the basic site (site of protonation) for these three lactams? And what should be their Brønsted ...
10
votes
1answer
310 views

Proton transfer equilibrium in bisulphite adducts

In the addition of $\ce{NaHSO3}$ to aldehydes and methyl ketones (higher ketones do not respond well to this reaction), crystalline addition products are formed. An $\ce{-SO3H}$ and an $\ce{-OH}$ ...
10
votes
3answers
12k views

Difference in acid strength of oxalic acid and malonic acid

Despite very similar skeletal structures, the difference in acid strength between oxalic acid (ethanedioic acid) and malonic acid (propanedioic acid) is quite significant. What is the reason for that? ...
10
votes
1answer
4k views

Order of Acidic strength: Phosphorus oxoacids [duplicate]

I was asked to compare the acidic strength of the following phosphorus oxoacids, I thought the order (of strength) would be $\ce{H3PO4 > H3PO3 > H3PO2}$, because they have three, two and ...
10
votes
1answer
175 views

Obtaining activity coefficients of conjugate acids of some common carboxylic acid molecules

Recently, I have been wondering about justifying the notion on how some common acids (e.g. carboxylic acids) are themselves weaker bases than water to the point that we don't usually consider them to ...
9
votes
3answers
969 views

What is the word for how polyprotic an acid is?

What is the word to describe the number of acidic hydrogens an acid has? I am currently thinking something like "proticity", but I am not sure The use case world be for a table of things like this: <...
9
votes
3answers
4k views

The pH of a neutralized solution

If pH is defined as the concentration of hydrogen ions in solution, then how can a ‘neutralized’ solution (defined as having an equal amount of hydrogen and hydroxide ions) have a pH other than 7? ...
9
votes
3answers
2k views

How can I make an acidic pen to burn paper on writing on it?

If I have a pen with refillable ink, can I just pour in concentrated Hydrochloric acid or concentrated sulfuric acid in the ink chamber to make it an acidic pen? Would it be better to use the acid of ...
9
votes
3answers
1k views

Oxalic acid structure

What is the reason why oxalic acid has its second $\ce{-COOH}$ group flipped? I'm guessing it's something to do with steric repulsions between the $\ce{-COOH}$ groups but I'm not sure.
9
votes
3answers
4k views

Acidity of o-halobenzoic acids

Rank the following compounds in decreasing order of acidity: 2-Fluorobenzoic acid 2-Chlorobenzoic acid 2-Bromobenzoic acid 2-Iodobenzoic acid My approach Since the ortho ...