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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Formation of zwitterion from amino acids

Why it is easier for the carbonyl group to lose a proton to become negatively charged and the amino group to accept a proton to become positively charged? I know it has to do with the very polar bond ...
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Mechanism for acid-catalyzed dehydration of 2,3-dimethylcyclopentanol

How do you get from 2,3-dimethylcyclopentanol to 1,2-dimethylcyclopent-1-ene? I know the -OH group leaves as water (being protonated by acid) forming a carbocation. Then the weak nucleophile (water) ...
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Carbon and dilute sulfuric acid

I have to distinguish between copper oxide and carbon. I thought of dilute sulfuric acid because it forms copper sulfate with copper oxide. But I don't know how carbon reacts with dilute sulfuric acid....
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Adjusting PBS with HCl: pH drift after dilution of phosphate buffer

It is some kind of everyday lab science and with a feel of shame I cannot answer this observation. I noticed a pH drift (~0.5 units) of my 10X phosphate buffer (PBS), when I adjust the pH with $\ce{...
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If the pH is zero, what would be the normality of a sulphuric acid solution?

If pH of the solution is zero, what would be the normality of $250 \, \mathrm{ml}$ $\ce{H2SO4}$ solution? My work: $\mathrm{pH} = 0$, hence the concentration of $\ce{H+}$ ions is $\pu{1 mol L^-1}$, ...
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Selective etchant for Al2O3 (Does not etch Al, Cu, Zn, Sn)

I'm looking for a wet-etchant to remove aluminum oxide created by anodizing, but not etch the unoxidized metal (with greater than 10:1 selectivity) I know about chromium(IV) oxide and fluorine-based ...
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Understanding sodium hydroxide drain cleaner's exothermic dissolution of aluminum; does the aluminum need to be oxidized before it dissolves?

I'm not a chemist but I remember that the standard HF/nitric silicon etch used in micro-fabrication supposedly worked in two steps; the HF would dissolve the thin SiO2 oxide layer on the silicon ...
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Why does saline have a pH of 5.5?

I am a physician and administer 0.9% NaCl in water ("normal saline") to patients frequently. The bag says it has a pH of 5.5 (compared to the human body of 7.4). I am asking why the pH is so low. It ...
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Colour change of fluorescein in acidic and basic medium

I prepared fluorescein for my chemistry project in school and I realised that this molecule and its preparation steps are very closely related to that of phenolphthalein. I have studied briefly about ...
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How to calculate the pH of a 0.325 M solution of pyridine hydrofloride?

How to calculate the $\mathrm{pH}$ of a $0.325~\mathrm{M}$ solution of $\ce{C5H5NHF}$? The $K_\mathrm{b}$ for $\ce{C5H5N}$ and $\ce{C5H5NH+}$ is $1.7\times 10^{-9}$. Here's my work, but it's wrong (...
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Is there a reliable chemical theory that predicts pKa based on structure?

Obviously, there are general stability arguments that can be made to estimate relative pKas, such as evaluating the stability of the conjugate base of an acid, or thinking about how polarized the bond ...
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Exceptionally weak basicity of pyridine [duplicate]

It is often explained that the relatively lower basicity of pyridine, relative to most amines, is due to the fact that the $\ce {N}$ lone pair resides in an $\ce {sp^2}$ hybridised orbital, instead of ...
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Does phosphoric acid remove stainless steel electropolished layer?

Electropolished stainless steel has a high corrosion resistance due to the oxide film that is created during electropolishing. The film mainly consist of chromium(III) oxide. Phosphoric acid is ...
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Why does potassium react the most vigorously with water?

Link to exam Which metal reacts most vigorously with water? (A) Ca (B) K (C) Mg (D) Na The given answer is B and the reasoning is that is is the most electropositive since it the furthest left and ...
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What is the pKa Range for weak acids and bases?

Am I correct in assuming that the following is true? $\mathrm pK_\mathrm a < 3$ is for a strong acid $3 < \mathrm pK_\mathrm a < 7$ is for a weak acid $7 < \mathrm pK_\mathrm a < 11$ ...
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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 ...
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Reaction of borax with NaOH

How does borax react with NaOH? My textbook says that sodium peroxoborate is formed. I couldn't find the reaction anywhere else. Can anyone verify as well as explain it?
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How to calculate the concentration H3O+ in a solution with pH=6.99?

What is the correct way to calculate the concentration $\ce{H3O+}$ in a solution with $\ce{pH}=6.99$? Attempt 1. pH<7, therefore there are only $\ce{H3O+}$ particles in the solution. $[\ce{H3O+...
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Why does pOH increase when pH decreases?

Let's say you add $\ce{HCl}$ to water. The $\ce{H+}$ ion concentration increases and that causes a decrease in $\mathrm{pH}$. But why would the $\mathrm{pOH}$ increase? I can't see why added $\ce{H+}$...
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Does H3O+ donate a H+ to Water?

Does the hydronium ion donate a proton to water? If the collision of 2 molecules of water can cause a proton to be transferred, does hydronium 'pass' a proton to water?
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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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Are all ionic compounds salts?

According to Wikipedia: A salt is an ionic compound that can be formed by the neutralization reaction of an acid and a base. Are all ionic compounds salts? Are all salts ionic compounds?
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Which definition of Acids and Bases conforms to the pH scale?

It's all in the title. Is it the Arrhenius or the Brønsted-Lowry definition? Or is it some other definition? Also, our teacher told us that $pH$ stands for "Power of Hydrogen", but some sources say ...
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Adding lemon to lentils changes color from black to pink, why?

I noticed that when I cook black lentils and add lemon juice to the water that's left, the water turns from black to pink! What can be the reason for that?
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Why can't alcohols turn blue litmus red?

I came across the fact that alcohols cannot turn blue litmus red. The fact confuses me as they are acidic and acids do turn blue litmus solution red. What prevents alcohols from turning blue litmus ...
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886 views

Does 99.8% acetic acid cause severe skin burns like formic acid?

I've so far handled only concentrated fuming nitric, sulfuric & hydrochloric acids from the inorganic side. Even during an accidental spill on the hand I did say only the $\ce{HNO3}$ affects the ...
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How to identify a redox reaction?

Which balanced equation represents a redox reaction? \begin{align} &\mathrm{A.} &\ce{AgNO3 + NaCl &-> AgCl + NaNO3} \\ &\mathrm{B.} &\ce{BaCl2 + K2CO3 &-> BaCO3 + 2KCl} ...
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How to compare the acidity of this multicyclic hydrocarbon to the acidity of cyclopentadiene?

This is the question: Which one is more acidic? According to me, cyclopentadiene should have been the answer, as losing a proton would make it aromatic; whereas the first option doesn't need ...
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Why is dimethyloxonium cation stronger acid than hydronium?

$\ce{(CH_3)_2O^+ H}$ has $\rm pK_a \; -3.8$ while $\ce{H_3O^+}$ has $\rm pK_a \; 1.74\;.$ So, the former is stronger acid than latter hydronium ion. But why is it so? Is it due to the $\rm +I$-...
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How to rationalise that when we dilute a weak acid, the pH increases but also the dissociation increases?

When water is added to a weak acid like ethanoic acid, the number of ethanoic acid molecules that dissociate increases, however, pH increases (less acidic), too. Why is this so?
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Comparison of acids to dissolve phosphates

I am currently reading this German paper on the dissolution of phosphates by acids and chelants. The authors do a "fast-test" of the dissolving power of different acids which goes as follows:...
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Odd Acidity Trend in Hexaaqua Metal Complexes

In the following link (three quarters down the page) it states that theoretically there should be a proportional relationship between the ionic radius and pKa of a hexaaqua metal complex (provided ...
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pH of dilute HCl solution [duplicate]

What is the pH of a solution of $3.4 \times 10^{-10}$ moles of $\ce{HCl}$ in a volume of $\pu{150.7L}$? This is dilute so I expect pH to be high. $$\frac{3.4 \times 10^{-10}\ \mathrm{mol}}{150.7\ \...
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Pipetting strong acid with plastic material

Can I pipette concentrated sulfuric acid using a plastic pipette tip? Will either the plastic or the acid be affected?
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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 ...
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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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Why alcohols don't behave as acids?

If I understand everything correctly, carboxylic acids behave like acids because oxygen is much more electronegative than hydrogen, so it takes his electron and releases H+. The problem is that ...
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Calculating pH of diprotic and amphoteric solutions

I am trying to understand this problem and its corresponding solution (complete solution not shown) First off, from the above one can see that the equilibrium constants when $\ce{H2ASO4-}$ donates ...
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How can I measure the pH of high-viscosity fluids like dough?

I would like to measure the pH value of dough with a pH-Meter, to ensure a pH value of 4.1 (max). Because of the high viscosity I would thin down the dough with demineralized water for two reasons: I ...
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In aminobenzoic acid, do we have three different pKa's?

In para-aminobenzoic acid, how can I know whether the amino group loses a proton or not when $\mathrm{pH}$ exceeds $8.5$? I have only found two values for $\mathrm{p}K_\mathrm{a}$ but I never found ...
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How are neutral amines effective bases in organic chemistry?

I have found it to be rather strange that neutral amines, such as triethylamine or DIPEA, find applications in organic chemistry in deprotonating alcohols or even α-carbonyl compounds. Amines are ...
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Which is the strongest base?

When I was in lower grades, I was taught $\ce{NaOH and KOH}$ are the strongest bases. But I realised later that there can be more stronger ones. After a bit of research on the internet, I found these ...
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If I mix carbon dioxide and sodium hydroxide in the right amounts in water, do I get baking soda?

Suppose I need a sodium bicarbonate solution (for non-food related reasons). Can I get something resembling it by mixing $\ce{NaOH}$ and $\ce{CO2}$ in water? Of course one should not attempt to make ...
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Why is the compound 3,4-dihydroxy-3-cyclobutene-1,2-dione more acidic than acetic acid?

Why is the compound 3,4-dihydroxy-3-cyclobutene-1,2-dione more acidic than acetic acid? I don't get how its resonance stabilization is far greater than that of acetic acid despite the fact that the ...
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1answer
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What is the difference between a reaction of Lewis acids with Lewis bases and a redox reaction?

For example I came across this equation: $\ce{2Al_{(s)} + 6HCl_{(aq)}} \longrightarrow \ce{2Al^{3+}_{(aq)} + 6Cl^{-}_{(aq)} + 3H_2_{(g)}}$ And thought this was a redox reaction but my book says it ...
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Why does ammonium carbonate smell?

Why is it that $\ce{(NH4)2CO3}$ smells while other salts with ammonium like $\ce{NH4Cl}$ does not smell? Does it have something to do with the equilibrium reaction? I know it has nothing to do with ...
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Can aluminum and hydrochloric acid be used to generate hydrogen gas?

I am looking to produce hydrogen gas in a small amount with supplies I currently have. Most of the methods I have seen involve reacting zinc or magnesium with $\ce{HCl}$ to obtain the gas, but I do ...
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Why is propanoic acid weaker than butanoic acid?

I was reading about electronic effects in organic compounds, and I found the explanation that carboxylic acids are weakening as their number of carbon atoms increase. But I found a table of $K_\...
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Why does chlorine undergo disproportionation in alkaline media?

One reaction used to form sodium hypochlorite (A type of bleach) is as follows: $\ce{2NaOH(aq) +Cl2(g)->NaOCl(aq) + NaCl(aq) + H2O(l)}$ Provided the sodium hydroxide is dissolved in some ...
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How useful is the assumption that water doesn't auto-ionize in the following?

Now in the first row of the iCe-table, $[\ce{H3O+}]$ is said to be 0. But water autoionizes to some extent, so it shouldn't really be 0. I accept that, because the pH of this solution is 2.5, the ...

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