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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12
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1answer
893 views

Nucleophilicity/basicity in protic and aprotic solvents

In polar aprotic solvent, why is $\ce{F-}$ a stronger nucleophile than $\ce{I-}$? What I think: If I talk about their basicity, $\ce{F-}$ would be more basic due to instability from its high electron ...
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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 $\ce{CHCl3}$, ...
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2answers
427 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
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2answers
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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
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1answer
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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 ...
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1answer
9k views

Relative acidities of alkanes, alkenes, and alkynes

How does one explain the trend in bond lengths and acidity of the following hydrocarbons? $$\begin{array}{ccc} \hline \text{Species} & \ce{C-H}\text{ bond length / Å} & \mathrm{p}K_\mathrm{a} ...
11
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1answer
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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,...
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4answers
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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
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1answer
518 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
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3answers
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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
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1answer
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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} $ ...
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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?
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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 $\displaystyle\ce{NaHCO3 -> Na+ + HCO3-}$...
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1answer
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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 ...
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1answer
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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 ...
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1answer
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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
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1answer
545 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 (&#...
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1answer
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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. ...
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2answers
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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 ...
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1answer
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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{...
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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 ...
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1answer
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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 ...
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3answers
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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 ...
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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 ...
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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 ...
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3answers
573 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 ...
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946 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, ...
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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 ...
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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 ...
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1answer
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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 ...
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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 ...
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1answer
225 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 ...
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1answer
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Why is H2SO4 a good dehydrating agent while other strong acids are not?

I understand that $\ce{H2SO4}$ is a very good dehydrating agent because it is a strong acid, so that it quickly donates $\ce{H+}$ to hydroxide ions in water to form $\ce{HSO4-}$ and $\ce{H3O+}$ .But ...
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1answer
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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 ...
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1answer
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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
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1answer
289 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 $\ce{-OH}$ ...
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Acidity order of nitrophenols

As in other posts I have seen and learnt that, if one is given four compounds, namely para-nitrophenol, ortho-nitrophenol, meta-nitrophenol and phenol and is told to arrange them in order of acidity, ...
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3answers
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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? ...
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1answer
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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 ...
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1answer
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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 ...
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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 ...
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952 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: <...
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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? ...
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3answers
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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 ...
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3answers
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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.
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Why is H2S2O7 stronger than H2SO4?

I've read that for an oxyacid, the oxidation number of the central atom shows the power of that acid, but here, the oxidation numbers of sulphur in sulphuric acid and pyrosulphuric acid are both the ...
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4answers
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Strong and Weak Acids/Bases

I'm so confused... $\ce{HClO}$ is a weak acid. then why is its conjugate base, $\ce{ClO-}$, a weak base in water? shouldn't they be inversely proportional? shouldn't $\ce{ClO-}$, be a strong base? ...
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2answers
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Why is the iodide anion a good nucleophile but a poor base?

The $\mathrm{pK_{aH}}$ of $\ce I^-$ is very low which indicated that it is not favourable for it to bond with a proton. However, why would it be likely to bond with any other atom (mostly carbon when ...
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1answer
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Is methanol really more acidic than water?

The question Why is methanol more acidic than water? deals with the reasoning of why methanol is more acidic than water. However, as mentioned in the comments of that question, the acidity constant of ...
9
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1answer
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Acid-base equilibrium of NH4CN

I'm having difficulties understanding this problem. We have in the problem that $K_\mathrm a$ for $\ce{HCN} = 6.2\cdot10^{-10}$ and $K_\mathrm b$ for $\ce{NH3} = 1.8\cdot10^{-5}$. Write chemical ...