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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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 ...
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How to calculate the pH of an acetic acid/ calcium acetate buffer?

Problem: A buffer was made by mixing $\pu{500 mL}$ of $\pu{1 M}$ acetic acid and $\pu{500 mL}$ of $\pu{0.5 M}$ calcium acetate. What are the resulting concentrations of acetic acid (henceforth ...
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How do I calculate the concentration of sulphuric acid by a titration experiment with sodium hydroxide?

In my latest chem lab the objective was to create a primary standard of $\ce{NaOH}$ and use it to determine the concentration of sulfuric acid. The first part of the lab was determine the molarity of ...
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991 views

Fitting titration curve

To simulate the action of gastric $\ce{HCl}$, we have titrated 100 ml of a meal with 0.1 N $\ce{HCl}$. To plot the data, use (R-code) ...
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How is the yellow colour of nitric acid removed?

Nitric acid obtained in laboratory is slightly yellow due to the dissolution of nitrogen dioxide which is produced due to thermal decomposition of a portion of $\ce{HNO3}$. $$ \ce {4HNO3 -> 2H2O ...
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106 views

Why does nitric acid have a different molecular structure from phosphoric and arsenic acids?

I remember that this really bugged me as an undergrad, and upon revisiting some inorganic chemistry notes I realized I still don't have a satisfactory answer for it. The structure of nitric acid, $\ce{...
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261 views

Is there a terminology contradiction about whether the conjugate of a strong acid is a “weak base”?

(Please note, I am not simply asking, "Is the conjugate of a strong acid a weak base?" I'm asking about the contradictory ways those terms seem to be used.) I was revisiting strong/weak acids/bases ...
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228 views

Why do these two calculations give me different answers for the same acid-base titration?

In class, I performed an weak acid-strong base titration using commercial white vinegar and sodium hydroxide with the aim of finding the concentration of of ethanoic acid in the vinegar, and I used ...
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173 views

Why would the loss of H₂ to space mean that the Earth's geochemistry would be based on acid/base reactions?

I am reading a paper[1] that contains the line: Most of the $\ce{H2}$ in the Earth's mantle escaped to space early in the Earth's history; consequently, the overwhelming majority of the abiotic ...
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305 views

Why is acetone less acidic than cyclohexanol?

The $\mathrm{p}K_\mathrm{a}$ of acetone is 19, whereas the $\mathrm{p}K_\mathrm{a}$ of cyclohexanol is 16. However, acetone is resonance stabilized and its major resonance structure displays the ...
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Reaction of aluminium trichloride with water

Since $\ce{Al^3+}$ is an acidic cation, shouldn't it react with water like this? \begin{align} \ce{AlCl3 + 6H2O &<=> [Al(H2O)6]^3+ + 3Cl^-} \tag1\\ \ce{[Al(H2O)6]^3+ +H2O &<=> ...
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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 ...
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Is the behavior of a dilute strong acid the same as the behavior of a weak acid?

My assumption is yes, as the $\mathrm{pH}$ levels of each will be similar and thus they have the same acidity. Is this correct or am I missing something?
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What's the pH of vinegar containg 5% acetic acid?

Vinegar generally contains 5% acetic acid. We would expect the pH of vinegar to be approximately: a. 0 b. 3 c. 7 d. 9 e. 12 I don't have the key for this question, so I just want to make ...
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Is ammonium a strong or weak conjugate acid?

Ammonium, $\ce{NH_4^+}$, is the conjugate acid of ammonia, $\ce{NH_3}$. I have searched the Internet and so many different answers pop up. The rule of thumb that I read was that a strong acid has a ...
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Why is CF3COOH exceptionally acidic?

The pKa values of almost all carboxylic acids lie much above 0. But this is violated by trifluoroacetic acid(-0.25). How can this be justified?
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Why amino acids (Zwitterion) become either negative or positive at low and high pH solutions?

The amino acids are Zwitterions. In neutral pH, an Amino acid's amino group has a postive charge and Carboxyl group has negative charge. They cancel each others charge thanks to the $Hydrogen$ that's ...
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Are all solutions of weak acid/bases buffers?

I am having a difficult time understanding what makes a buffer a buffer. Buffers in my textbook are defined as a solution of a weak acid or base and their conjugate acid/base. So if I were to just ...
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790 views

Choice of base for malonic ester synthesis

Most reaction mechanisms use $\ce{EtO-}$ as a base to deprotonate the alpha hydrogen in the malonic ester sythesis. But in the equilibrium there are still esters that haven't been deprotonated. Why ...
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334 views

Why are lactate and lactic acid used synonymously in biochemistry?

In science there's always a misuse of the two terms. I know that lactate is the conjugate base of lactic acid. Why are they used like is the same thing? For exemple: in lactic acid bacteria (LAB) ...
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Short Cut Method to Calculating pH of Polyprotic Acid?

I am doing the following question: Calculate the pH of a $4.00\ \mathrm{mol\ L^{-1}}$ solution of citric acid. $\mathrm{pK_{a1}} = 3.09~~~~~ \mathrm{pK_{a2}} = 4.75~~~~~ \mathrm{pK_{a3}} = 6.40$ ...
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Is calcium chloride an acidic or basic salt?

What I reason: Calcium chloride is the salt of hydrochloric acid and calcium hydroxide. Calcium hydroxide is usually not considered a strong base, and I believe this is because of it's low solubility. ...
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Combining acid dissociation constants to determine pH of diprotic acid

If I have a diprotic acid with $K_{\mathrm{a1}}$ and $K_{\mathrm{a2}}$ as the acid dissociation constants, why can't I calculate the final $\mathrm{pH}$ using $K = K_{\mathrm{a1}}\cdot K_{\mathrm{a2}}$...
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Why isn't N2 a Lewis base?

Why is $\ce{N2}$ (dinitrogen) not a Lewis base even with two lone pairs?
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Storing large quantities of KOH

I need to handle large quantities of $\ce{KOH}$; close to 1000 liters of 85 % conc $\ce{KOH}$ for about an hour. Any suggestions on how I go about doing it? Also the temperature during the process ...
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How does aqua regia dissolve gold?

I recently learned that aqua regia can dissolve less reactive or noble metals like gold. Aqua regia is a mixture of $\ce{HCl}$ and $\ce{HNO3}$, but separately, neither of these acids dissolve gold. ...
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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 ...
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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 ...
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Can someone please explain buffers to me?

This is what I understand so far: The concept of a buffer is to minimize any swings in pH. In order to do this you need to create a solution with both acidic and basic compounds. To create one, you ...
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Are there any amphoteric substances other than water and ammonia?

I have read about the Brønsted-Lowry and Arrhenius concepts to define a substance as an acid or a base. Our teacher told us that there are substances which behave both as an acid and a base, using ...
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Why does polonium form acidic oxides?

All metals form basic oxides. Metallic oxides are basic in character. Polonium is a metal, so it should form basic oxides but it forms acidic oxides. Why are its oxides acidic in character?
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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 ...
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How are these compounds strong bases, when they are sparingly soluble in water?

How is it possible that some insoluble compounds in water, e.g. $\ce{Mg(OH)2}$, $\ce{Ca(OH)2}$, $\ce{Sr(OH)2}$ are considered strong bases? Are they even strong bases? How can I tell if a compound is ...
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Is it correct to say that H2SO4 is an acid in this reaction?

Is it correct to say that $\ce{H2SO_4}$ acts as an acid in the following reaction? $\ce{2Ag + H2SO_4} \rightarrow \ce{Ag_2SO_4 + 2H_2O + SO_2}$ I know it acts as an oxidizing agent, but is it ...
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Reaction of Iron(III) with hydroxide ion

The observations: 1) Treatment of 1 mL of 0.05 M $\ce{Fe(NH4)SO4}$ solution with excess 1 M $\ce{NaOH}$ results in the formation of a rust-colored red-brown iron-based solution with many suspended ...
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Amount of Phenolphthalein required

We just had chemistry practical few days a go. The topic was strong acid-base titration, in which we had to find the normality and concentration of $\ce{HCl}$. My teacher instructed me to add 2 drops ...
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336 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?
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988 views

Basicities of nitrogen atoms in purine

Arrange the sites in purine in order of basicity. I feel that 9 is the least basic as nitrogen's lone pair is delocalised. However, I am unable to rank 1, 3, and 7 in a particular order. Is ...
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Comparing basicity of imidazole and 2-imidazoline

I recently sat for an exam in which I was asked to compare the basicity of the above compounds. I thought imidazole would be more basic because it is aromatic but according to the answer key 2-...
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Comparing pKa of hydrocarbons

We have to compare their acidic strength, and we know acidic strength is directly proportional to stability of the anion. So the first compound is more acidic due to its being aromatic after ...
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What bases are fit for human consumption and can be used in foods?

I know that are several acids that can be found in the kitchen, such as citric acid and vinegar. However, I never heard of a base that can be used in the kitchen to raise the pH levels of any food. ...
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pKa values for protonated nitrogens in ketoconazole

Everywhere on the internet I see that the two $\mathrm pK_\mathrm a$'s of ketoconazole are 6.4 and 2.3, but I don't think that is correct. The $\mathrm pK_\mathrm a$ of imidazole is around 6.4 . ...
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Can I make a buffer from two different weak acids or bases?

Can I make a buffer using two different acids/bases? For example, adding 1 mole of acetic acid and 1 mole of ammonia? The only information I can ever find is that I can make a buffer using only an ...
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What is the acid dissociation constant of cacodylic acid?

What is the $\mathrm pK_\mathrm a$ of cacodylic acid? I cann't seem to find one answer on the internet. I have read 1.67, 6.37, and 4.8 in my $\mathrm pK_\mathrm a$ table. What is the reason for this? ...
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To add acid or base to water

There is a rule stating that we shall add a strong acid to water, and not the other way because of safety; if we would add water to the acid, the reaction could be dangerous (boil). What about adding ...
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Why will CuSO4 solution be acidic?

An end-chapter problem posed in an 11-grade texbook asks to analyse whether a water solution of CuSO4 will be acidic. The standard answer is yes, because "$\ce{H2SO4}$ is a strong acid, hence $\ce{...
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884 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 ...
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Why is glycine hydrochloride more acidic than chloroacetic acid?

I cannot figure out why glycine hydrochloride is more acidic than chloroacetic acid. Could I have figured this out from a $\mathrm pK_\mathrm a$ table and maybe am just not seeing it? On the table I ...
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318 views

How can I determine the pH of solution?

Could anyone tell me how I would go about calculating the pH of 100.0 mL of 0.100 M $\ce{H2NNH2}$ ($K_\text{b} = 3.0 \times 10^{-6}$). Furthermore, how would this pH change when 20.0 mL of 0.200 M $\...
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Why don't Gringard Reagents react with carbonyls at the alpha position? [duplicate]

According to many texts, the reason why Gringard reagents cannot be used with alcohols is because the Gringard reagent is a strong base, which would deprotonate the alcohol. ($p\pu{K}_b$ of Gringard $\...