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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11
votes
1answer
705 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 (&#...
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
3answers
721 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 ...
8
votes
3answers
40k views

Calculating Buffer Capacity

I completed a titration of Ammonium Acetate buffer solution and to it I added $\pu{2M}$ Hydrochloric Acid. I measured the initial $\ce{pH}$ of the buffer solution before any acid was added and I ...
8
votes
2answers
21k views

Why is benzoic acid a stronger acid than acetic acid?

Why is benzoic acid ($\mathrm{p}K_\mathrm{a} = 4.20$) a stronger acid than acetic acid ($\mathrm{p}K_\mathrm{a} = 4.76$), even though the conjugate base in case of benzoic acid is destabilized due to ...
7
votes
1answer
406 views

t-BuOK as a base

I thought $\ce{KOtBu}$ was used to form the less substituted alkene. Why is that not the case here?
6
votes
3answers
28k views

Is magnesium sulfate basic, neutral or acidic?

A question in my college test was whether $\ce{MgSO4}$ is neutral, acidic or basic. I was told to solve this kind of problem by hydrolyzing any ions that do not "come from" a strong acid or a strong ...
6
votes
2answers
566 views

Comparing basic strength of nitrogen heterocycles

Compare the basic strength of the following compounds: d > b > c > a c > b > a > d c > a > b > d a > d > c > b I know that in compound (c), the π-bond between nitrogen and ...
6
votes
3answers
2k views

The nomenclature of mineral acids

My basic knowledge about nomenclature is: A mineral acid is called hypo when it has one less oxygen than the original one, a pyro acid when 2 molecules of acid add up with release of $\ce{H2O}$ a ...
5
votes
5answers
4k views

Which proton in cyclohexene is the most acidic?

I know that $\mathrm{H^b}$ is most acidic due to conjugation (resonance). But I am confused as to how to compare $\mathrm{H^a}$ and $\mathrm{H^c}$. I think $\mathrm{H^a}$ should be more acidic than $\...
5
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2answers
4k views

Solvent effects on acidity of ethanoic acid

Is ethanoic acid most acidic in DMSO, water or methanol? I suspect that the conjugate base would be most stabilized by a polar protic solvent (meaning it's weakest in DMSO), however, water and ...
5
votes
4answers
28k views

What is the pH of a 5M solution of hydrochloric acid?

What is the $\mathrm{pH}$ of a $\pu{5M}$ solution of hydrochloric acid? So in order to solve this, apparently all you need to do is plug it into the equation: $$\mathrm{pH} = -\log[\ce{H3O+}]$$ ...
4
votes
1answer
4k views

Which is more basic, piperidine or pyrrolidine and why?

Pyrrolidine seems to be less basic as it is a 5-member ring and +charge on N atom won't be stable due to steric factors as compared to piperidine but the results are opposite.
4
votes
1answer
4k views

Friedel-Crafts alkylation of five-membered heterocycles

The five-membered heterocycles pyrrole, furan, and thiophene undergo Friedel-Crafts acylation, but I have not seen them undergoing a simple Friedel-Crafts alkylation reaction with a Lewis acid such as ...
3
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2answers
1k views

Interesting ionization of sulfuric acid

I just need an explanation of why it is a strong acid in its first ionization and a weak acid its second ionization. It becomes $\ce{HSO_4-}$. From what I have learned about oxoacids, the bond ...
2
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2answers
11k views

Field Effect and it's effect on basicity on amines

What is the order of basicity between $\ce{Me2NH}$, $\ce{Me3N}$, $\ce{MeNH2}$ in a protic solvent. It has something to do with field effect which I could not understand and could not find anywhere. ...
2
votes
2answers
9k views

Is H+ (in an aqueous solution) = H3O+? [duplicate]

I was learning about autoionization in science and my science teacher wrote $\ce{H3O+}$ as $\ce{H+}$ — now, my intuition would lead me to assume that: $$\ce{H3O+} = \ce{H+}$$ But, $\ce{H+}$ is just ...
2
votes
3answers
10k views

Why are acid-base reactions so exothermic?

If I mix sulfuric acid with sodium hydroxide, the solution really heats up. Could someone explain why acid-base reactions are exothermic from a molecular perspective?
1
vote
2answers
111 views

Which rate, the forward or reverse rate of acid dissociation, is more strongly affected when diluting acetic acid in aqueous solution?

Acetic acid is a weak acid. It is in equilibrium with acetate and hydronium ions in aqueous solution: $$\ce{CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)}$$ Ostwald's law states that the ...
1
vote
1answer
151 views

Can acid-base reactions occur in a non-aqueous medium?

To better illustrate my question, allow me to refer to the case of ammonium chloride, formed through a classic acid-base reaction. The reaction between ammonia and hydrogen chloride to give ammonium ...
1
vote
1answer
1k views

Which pH approximation to choose when?

When I learned about pH approximations in school, I was told that each approximation fits to a certain acidity strength/pKa range. Those ranges are grouped in common categories (pKa borders are only ...
1
vote
1answer
25k views

How to calculate the concentration of all relevant species in a buffer of a given pH?

You prepare $1.0~\mathrm{L}$ of a $0.25~\mathrm{M}$ acetic acid solution with a final $\ce{pH}$ of $6.0$. What are the molar concentrations of all relevant acetic acid species ($[\ce{HA}]$ and $[\ce{A-...
0
votes
1answer
410 views

What is the nature of the mysterious Kw, the ionic product of water?

In pure water, [H$^+$] = 10$^{-7}$ M and [OH$^-$] = 10$^{-7}$ M. So, we conclude pH of water is 7 and so is the pOH. We define the ionic product of water as Kw = [H$^+$][OH$^-$] = 10$^{-14}$ M$^{2}$. ...
16
votes
1answer
1k views

What is the oxidation state of Mn in HMn(CO)5?

What is the oxidation state of $\ce{Mn}$ in $\ce{HMn(CO)5}$? If $\ce{H}$ has an oxidation state of $+1$, then $\ce{Mn}$ should have oxidation state of $-1$, which I'm not sure is possible. On the ...
14
votes
2answers
26k views

Does bleach (without rinsing) leave residues and can vinegar, baking soda neutralize them?

It's very difficult to get accurate information concerning household bleach residues. Imagine, for instance, that you pour pure (or diluted) bleach onto fabric or synthetic foam and let it dry without ...
12
votes
1answer
2k views

Explanation of Lemon Juice-Invisible Ink

A cute homegrown spy-trick we all know: lemon juice invisible ink. But there is no scholary article available in the internet about this phenomenon. A rough explanation I found in Scientific American:...
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 ...
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 ...
9
votes
1answer
5k views

Why is carbonic acid a weaker acid than acetic acid?

Is it because the $\ce{OH}$ group next to $\ce{COOH}$ in carbonic acid donates electron density to the $\ce{COO-}$ by resonance, making it a stronger base, compared to a weaker electron donating ...
7
votes
1answer
6k views

How does H2SO4 dissociate?

Apologies for this extremely basic question, I'm just beginning with Chemistry so please don't be too harsh on me. My book says that sulfuric acid, $\ce{H2SO4}$, dissociates in its ions following ...
7
votes
2answers
9k views

Why is p-methoxyphenol more acidic than p-methylphenol?

Why is p-methoxyphenol more acidic than p-methylphenol? According to me, inductive effect really doesn’t matter at para positions and p-methoxyphenol should be less acidic due to the high mesomeric ...
6
votes
3answers
4k views

Aqua regia and nascent chlorine

Aqua regia has the famous property of being able to dissolve noble metals, like gold and silver. I read that this has to do with the generation of nascent chlorine. How does this happen and how does ...
6
votes
2answers
1k views

Sodium Polysulfide production from NaOH and Sulfur

Does the sulfur also oxidize the $\ce{OH-}$ radicals after the $\ce{Na2S4}$ chains form? Something like this: $$\ce{9S + 4NaOH -> 2Na2S4 + SO3 + H2O}$$
5
votes
1answer
4k views

Why is lemon mixed with water considered alkalizing water?

The benefits and facts of alkaline water are often skewed due to the marketing of companies and uneducated hype for the innocent idea of unlimited potential. I wanted to know the specific reactions ...
5
votes
1answer
1k views

Comparing the basicity of benzamide and acetamide

What if we were asked to compare the basicity of benzamide and acetamide? Which one of them would be more basic? I read somewhere on the internet that benzamide must be more basic than acetamide due ...
5
votes
1answer
2k views

Why does H bond to S in HSO3?

In the structure of $\ce{HSO3-}$, we see that the H is bonded directly to the S, not to the O's, as would be the case in other oxyacids. Why is this the case?
4
votes
1answer
1k views

Is this the correct relative Brønsted acidity in these four acids?

We are asked to sort these four acids by increasing Brønsted acidity: The problem is, I am confused why $\ce{H2F+}$ is the strongest acid of them all. I understand that stronger acids will have ...
4
votes
3answers
5k views

pKaH of pyridine versus other imines

Why is pyridine so much more acidic than other similar imines (5.5 versus ~9, see picture)? Wouldn't delocalization of the positive charge into the aromatic system stabilize it and hence decrease ...
3
votes
2answers
1k views

Calculating vinegar strength

The pKa of vinegar is 4.76. If I know the pH of the vinegar, what would be the formula for determining the percentage acid base on the relationship between pH, pKa and concentration? Can you show the ...
3
votes
1answer
10k views

Making carbon monoxide gas from formic acid and sulfuric acid?

Can I create carbon monoxide gas by just mixing formic acid and sulphuric acid together? Or do they have to be heated?
3
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3answers
8k views

Are acid chlorides really acidic?

If I test a pure solution of an acid chloride with a pH-meter, will I get a reading of pH 7? When I add water to it, I know $\ce{HCl}$ gas will form, but this gas will dissolve in water to give an ...
3
votes
1answer
6k views

I need to find the Ka of a weak acid in titration with a strong base

I have been working on this lab forever and have not been able to get a $K_\text{a}$ anywhere close to the accepted value. I’m sure I’m missing something really simple. We titrated $\ce{CH3COOH}$ ...
3
votes
1answer
176 views

are half of “H2SO4 pH sample problem” webpages just wrong, or am I wrong?

I did a Google search for "h2so4 pH sample problem" and went through the results, and it looks like about 50% of the webpages "explaining" how to do this problem give the wrong answer when calculating ...
3
votes
2answers
203 views

What is the difference between these equations for the Contact process?

Some webpages describe the contact process as this (I left out $\ce{SO2}$, $\ce{SO3}$ production): $\ce{SO3 + H2SO4 -> H2S2O7}$ After this, it is controllable to add water to the oleum therefore ...
3
votes
1answer
4k views

Why are amidines so much more basic than amides?

Both delocalize the added proton. Is it because the bond lengths in amidines are the same, or perhaps because oxygen is more electronegative than nitrogen and thus is more reluctant at keeping the ...
3
votes
0answers
931 views

Rationalizing Acidities of Ammonium Ion and Hydronium Ion

Stumbled across this interesting practice problem in my organic textbook. I have a few reasons for why $\ce{H4N+}$ is less acidic than $\ce{H3O+}$. 1) Let’s assess conjugate stability first. ...
3
votes
1answer
110 views

Why is the maximal percent concentration of acids similar to their molar mass

Why is the usual percent concentration of a concentrated acid's solution similar to its molar mass? For example: ...
2
votes
2answers
886 views

Balanced equation for neutralisation reaction betweeen potassium carbonate and hydrochloric acid

They seem all correct to me, is there any reason why one reaction would happen over the other(s)? $$\begin{align} \ce{K2CO3 + 2 HCl &-> 2 KCl + H2CO3}\\[6pt] \ce{K2CO3 + 2 HCl &-> 2 KCl ...
2
votes
1answer
555 views

Why are weak acids not considered good leaving groups?

So today in my first year lecture my professor said that weak bases are good leaving groups. I understand why they are good leaving groups in comparison to unstable strong bases but why are weak acids ...
2
votes
2answers
728 views

NaHCO3 required to raise pH of weak HCl solution from 3.5 to 7.2 (doubting my calculations)

I'm a dentist, working on a medical device that will make shots at the dentist office hurt a lot less. The device mixes a drug (2% Lidocaine) that has been acidified with $\ce{HCl}$ to pH 3.5 for ...

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