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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10
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3answers
11k 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
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3answers
597 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
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2answers
18k 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 ...
8
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3answers
38k 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 ...
7
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1answer
346 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
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3answers
25k 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
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3answers
1k 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 ...
6
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2answers
389 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 ...
5
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4answers
25k 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
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1answer
3k 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.
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
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3answers
8k 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?
2
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2answers
8k 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 ...
1
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1answer
24k 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-...
1
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2answers
82 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
281 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$^{2}$. ...
1
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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 ...
14
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2answers
23k 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
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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
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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 ...
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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
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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
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4answers
901 views

Do enolates get protonated at the carbon or oxygen atom?

An enolate has two resonance structures. When it gets protonated, where is the $\ce{H+}$ more likely to go? On the oxygen to produce an enol, which tautomerizes to the keto, or on directly onto the ...
7
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2answers
8k 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 ...
7
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1answer
4k 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 ...
6
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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
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2answers
906 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: $$\ce{9S + 4NaOH -> 2Na2S4 + SO3 + H2O}$$
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1answer
712 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
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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
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1answer
811 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
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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
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
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0answers
864 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
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3answers
7k 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
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1answer
124 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
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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
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2answers
148 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
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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
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1answer
109 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
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0answers
189 views

How to determine the strongest oxyacid of chlorine without being given the acid dissociation constant data? [duplicate]

I was told to find the strongest and weakest acids out of $\ce{HCl, HClO, HClO2, HClO3}$, and $\ce{HClO4}$. I knew that $\ce{HClO}$ was the weakest but was stuck between $\ce{HCl}$ and $\ce{HClO4}$ ...
2
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1answer
147 views

Conversion of CO2 to methane

Suppose one could generate an enzyme with arbitrary conditions at the active site. What conditions would then be necessary to cause carbon from dissolved $\ce{CO2}$ in low $pH$ water to combine with ...
2
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2answers
707 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
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1answer
444 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
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1answer
3k views

Why does a buffer work best at the pH closest to its pKa?

I think I'm having trouble understanding exactly how the pKa relates here on a conceptual level. For example I know that carbonic acid works somewhat well as a buffer at pH near 7, since its pKa is ...
2
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1answer
942 views

Where does the sulfuric acid, used in Contact Process for manufacturing sulfuric acid, come from?

If Contact process is used for manufacturing sulfuric acid, then where does the sulfuric acid used in the process itself come from? The following is from wikipedia page for Contact Process : Hot ...
1
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1answer
162 views

Finding pH of tri-protic acid

I am studying for my final and I am given this problem: A solution of sodium phosphate is made from 10.5 g sodium phosphate in 150 mL of water. What is the pH of this solution Given: Ka1, Ka2. ...
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2answers
11k views

MaVa = MbVb - Limitations and Uses

We know that for strong acids with a $1:1$ mole ratio between all particles involved are suitable for use with the aforementioned formula for titration problems. I want to know the limits on this ...
1
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2answers
498 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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1answer
5k views

Why do carbon dioxide and sodium hydroxide not form sodium oxide and carbonic acid?

Why do carbon dioxide and sodium hydroxide not form sodium oxide and carbonic acid? $\ce{CO2 + 2NaOH -> Na2O + H2CO3}$ as opposed to: $\ce{CO2 + 2NaOH -> Na2CO3 + H2O}$ This is in the ...