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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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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What is the meaning of cmmol in chemistry?

I came across a unit called $\text{cmmol dm}^{-3}$ in buffer solutions. What does this unit mean?
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Reactions of alkynes with sodium/ammonia vs sodium amide

What happens when alkynes react with sodium in ammonia ($\ce{Na/NH3}$), or when they react with sodium amide ($\ce{NaNH2}$)? Are these two sets of conditions different?
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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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Why does ammonia accept a hydrogen to form ammonium when its octet is already complete?

Why does ammonia accept a hydrogen to form ammonium when its octet is already complete as $\ce{NH3}$ and it should be, seemingly, stable as $\ce{NH3}$?
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What exactly is basicity?

In my textbook, it’s given that the trend of the basicity of the elements of group 15 is $$\ce{NH3 > PH3 > AsH3 > SbH3 \ge BiH3}$$ Also, it’s said that the reducing character decreases down ...
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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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Why is HCl a stronger acid than Acetic Acid?

Drawing the conjugate bases, Oxygen is more electronegative than Chlorine so negative charge on Oxygen is more stable than Chlorine, Thus My argument that Acetic Acid is more acidic. Also the O¯ ...
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322 views

Which is more basic: 1,2‐dihydropyridine or 1,4‐dihydropyridine?

Which compound is more basic of the two? My thinking: In compound A, the lone pair of nitrogen are in resonance with two other double bonds. The resonance chain here seems to be longer as ...
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Comparing acidity of anilinium ion and para-fluoro anilium ion

Which of these compounds - anilinium ion and para-fluoro anilium ion - is more acidic? I thought the answer would the be first one since $\ce{-F}$ is an ortho-para activating group, so the electron ...
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Volume required to dilute solution for a pH change

A $\pu{100 mL}$ solution of $\ce{NaOH}$ has a $\mathrm{pH}$ of $13$. What volume of water in $\pu{mL}$ must be added to change the $\mathrm{pH}$ to $11$? My steps: Begin by calculating conc. of $[\...
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Which species dissociate completely in ionic equations?

I am tasked with writing a molecular equation, an overall ionic equation, and a net ionic equation for the reaction between an aqueous solution of phosphoric acid, $\ce{H3PO4{(aq)}}$ and an aqueous ...
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Acidity order of 4-halophenols

How do I theoretically predict the acidity order of the following para-halophenols? (experimental $\mathrm{p}K\mathrm{a}$ values beside each) parafluorophenol (9.92) parachlorophenol (9.41) ...
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How to determine the pH of a mixture of two weak acids?

We’ve two solutions: Solution 1 $\ce{HCOOH}$ its concentration is $c_1=10^{-2}\ \mathrm{mol/l}$ and its volume is $V_1 = 50\ \mathrm{ml}$ and its $\mathrm{pH}_1 = 2.9$. Solution 2 $\ce{CH_3COOH}$ ...
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Rate and mechanism of the reaction of Mg and HCl

In the reaction between hydrochloric acid and Magnesium the overall reaction is: $$\ce{Mg + 2HCl -> MgCl2 + H2}$$ My proposed mechanism of reaction is that $\ce{HCl}$ dissociates in $\ce{H2O}$ ...
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What is the most acidic neutral hydrocarbon?

This is a question I've been thinking about quite frequently. I had seen that this hydrocarbon has a low $\mathrm pK_\mathrm a$ with reference to the highlighted H-atom Loss of the central gives ...
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Acidity of cyclopentadiene when fused to benzene rings

Why does fusion to a benzene ring reduce the acidity of a cyclopentadiene ring? For example, acidity decreases going from cyclopenta-1,3-diene to indene and to fluorene:
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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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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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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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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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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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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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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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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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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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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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Why can the acidic strength between H2S and HCl be explained on the basis of electronegativity but H2S and H2O can't?

Consider simply aqueous solutions of $\ce{H2S}$ and $\ce{HCl}$ . It is pretty much known that $\ce{HCl}$ is stronger than $\ce{H2S}$ in water. The reason behind that first is the electronegativity of ...
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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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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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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 ...