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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Removing alkaline stain with acid
Professor Robert Winston once removed a blue alkaline stain using carbon dioxide from a fire extinguisher on James Corden's show. Here's the link for the episode
I would like to know if there is a way ...
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Why is hydrogen peroxide acidic in aqueous solution?
This seemed like a trivial question to me... until I began to think about it.
The "usual" criteria for greater acidity are larger sizes of the atom attached to the acidic proton within the ...
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What is the basicity order of peroxide, superoxide and hydroxide anions?
My teacher told me superoxide and peroxide anion are more basic than hydroxide but according to Wikipedia
Given that the hydroperoxyl radical has a pKa of around 4.8
and and pKa of H2O is
Acidity (...
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29 views
Why indium and thallium doesn't react with alkali solution? [closed]
It is given in my book that ' In Boron family, only Aluminum and Gallium reacts with alkali solution and not Indium and Thallium'
What makes indium and thallium unreactive to alkali solution?
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How to reduce the acidity of vinegar, without diluting it? [closed]
Ive been drinking a small amount of vinegar for possible health benefits.
I would like to reduce the acidity, to enhance tolerability in the body.
But I dont want to dilute it too much, as the ...
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47 views
pH after adding acid to soil [closed]
I am working on a question of Regional Junior Science Olympiad.
I have actually no idea how should I begin. Please guide me.
For details, here is the main question
Plants absorb several ions and ...
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43 views
Would para-aminobenzoic acid exist as a zwitterion or non-ionized at pH 4?
The two $\mathrm{p}K_\mathrm{a}$ values for p-aminobenzoic acid (PABA) are: $\mathrm{p}K_\mathrm{a1} = 2.50$ and $\mathrm{p}K_\mathrm{a2} = 4.8$.
My thought was that at a $\mathrm{pH}$ of 4, the ...
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comparing acidity of oxonium cations ( conjugate acid of ketone, ether and alcohol)
I read that alcohol is the most basic among alcohol, ether, aldehyde and ketone.
I am curious about the reason and I found the pKa of their conjugate acids:
It makes me wonder: why is the ethanol ...
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29 views
Why does the basic properties of oxides of transition metal increase downwards?
I was solving questions on d-block elements and I got a question that asked for the order of basic properties of $\ce{ZrO2}$ & $\ce{HfO2}$.
Based on what I have learnt, the size of zirconium and ...
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1answer
701 views
Is powdered acid dangerous? [closed]
I was told that an acid is only dangerous because it releases $\ce{H+}$ ions when in contact with water.
Therefore, powdered acid should be completely safe on skin provided that your skin is not ...
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How to separate Cu and Ni from alloy containing different metals such as Al, Cu, Ni, (Zn, Pb, Sn < 5%)?
I have an alloy containing different metals such as Al, Cu, Ni, (Zn, Pb, Sn, Ag, Si in small amount < 5%). How can I separate Cu and Ni from this alloy?
I tried to dissolve alloy in sulfuric acid, ...
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48 views
Towards a hard Lewis base like water which is the stronger Lewis acid, silicon tetrachloride or tin (IV) chloride?
On Pauling scale, both $\ce{Si}$ and $\ce{Sn}$ have electronegativity value of $\mathrm{1.9}$. The difference is in size of d-orbitals which accept lone pair of electrons. $\ce{Si}$ has vacant 3d-...
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1answer
57 views
How exactly does a buffer made up of a weak acid and its conjugate base work upon addition of hydroxide ions? [duplicate]
Consider a buffer solution containing a weak acid and its conjugate base ($c_\mathrm{total} = \pu{0.1 mol L-1}$):
$$\ce{HA <=> H^+ + A^-}$$
When $\ce{H+}$ ions are added (from a strong acid), ...
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Why do we care about H+ ions and not other ions in water? [duplicate]
Water autoionizes into H+ and OH-. At equilibrium the product of concentrations of ions is 10e-14.
If [H+] is greater than 10e-7 we call it acidic.
I can't help but wonder why we pay so much attention ...
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Gibbs free energy of mixing in a control volume
I'm trying to model the amount of energy lost due to mixing of a $\mathrm{HCl}$ solution using the Gibbs free energy of mixing. However, I really like a second opinion on the model and the results, ...
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Does amide ion prefers to act as a base than a nucleophile?
In this question, I think that amide ion, being a good nucleophile should attack on the terminal carbon through $\mathrm{S_N2}$ mechanism to form compound (c), but the answer given is (b), and the ...
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How are protons transferred from an acid to a base in aqueous solution?
I have read in my textbook that an acidic proton is transferred to a base through direct contact. Since acid is ionized in water, wouldn't it be more likely that the surrounding water molecules become ...
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1answer
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Would a solution with a hydronium concentration of 1e-10 be basic? [closed]
So obviously the pH of the solution would be 10, which is basic on the scale. But isn't adding hydronium ions to a neutral solution that is water fundamentally acidic.
Or is it that water itself has a ...
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1answer
61 views
Why does adding excess NaOH prove amphoteric nature?
When 3+ hexaaqua ions react with hydroxide ions, the following set of reactions occurs:
When we get to stage 3, a neutral ion has formed, and a white precipitate is created. Now, we know that for ...
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39 views
Why is 4-hydroxyacetophenone more acidic than 3-hydroxyacetophenone? [closed]
At 25 °C, the $\mathrm{p}K_\mathrm{a}$ of 3-hydroxyacetophenone is 9.19, while the $\mathrm{p}K_\mathrm{a}$ of 4-hydroxyacetophenone at the same temperature is 8.05. Why is that so?
3-...
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Why does HCl act as a weak base in HF solvent, even though it is a stronger acid compared to HF?
I've read that $\ce{HCl}$ acts as a weak base in $\ce{HF}$ solvent, which means $\ce{HCl}$ is supposed to lose $\ce{H+}$ ion to $\ce{HF}$. $\ce{HF}$ is a weak acid compared to $\ce{HCl}$, then shouldn'...
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What is the relation between strength of a base and the thermal stability of its salts?
In Concise Inorganic Chemistry, $5^{th}$ edition, by JD Lee, while discussing oxides and hydroxides of Group $2$ metals, it has been stated that:
The increase in basic strength is illustrated by the ...
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Understanding equivalence point [closed]
I read this passage:
“It is important to emphasize that, while a strong acid/strong base titration will have its equivalence point had a pH of seven, the equivalence point does not always occur at pH ...
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1answer
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Strongest acid that can exist in water
Fundamentals of Biochemistry: Student Companion: Life at the Molecular Level[1] states that,
The strongest acid that can stably exist in aqueous solutions is $\ce{H3O+}$.
This is restated in the ...
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1answer
90 views
Calculating pH of aqueous ammonium hydrogen sulfide solution
I was doing the following question yesterday:
Calculate the pH of a $\pu{0.1 M}$ solution of $\ce{NH4HS}$, given $\mathrm{p}K_\mathrm{b}$ of $\ce{NH3}$ is $4.74$, and $\mathrm{p}K_\mathrm{a1}$ and $\...
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1answer
36 views
How to dissolve brass surrounded by aluminium?
I have a broken off brass needle stuck in a caste aluminum hole. (It’s the pilot mixture jet on a carburetor).
I was wondering if there was a chemical that would dissolve the brass while not reacting ...
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49 views
What happens to water and oxygen produced due to dissociation of nitric acid? [closed]
Nitric acid is yellow in colour due to the dissolution of nitrogen dioxide gas.
The nitrogen dioxide is obtained due to thermal dissociation of a portion of nitric acid:
$$\ce{4HNO3 -> 2H2O + 4NO2 +...
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Is “Sulfuric acid… makes a poor electrolyte… very little of it will dissociate into ions” really true? What does that actually mean?
While researching chromate conversion coating for edits to this answer in Space Exploration SE, I came upon the following passage in Corrosion Resistance of Stainless Steel to Sulfuric Acid
Sulfuric ...
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How measured content of Calcium Carbonate in eggshells change with the use of different acids?
I am investigating the calcium content of chicken eggshells. The only literature I can find on this consistently and solely depend on the use of HCl to conduct back titration. I conducted the ...
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Anti-foaming agent for HCl + copper chloride solution
I am trying to etch my own circuit boards at home, and have whipped up some DIY cupric chloride etchant (just CuCl with a bunch of free HCl)
The problem I have found is that when I try to bubble air ...
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1answer
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How to calculate Kp without knowing the volume? [closed]
I have the following chemical equation:
$$\ce{Sb2S3 + 3H2 <=> 2 Sb + 3H2S}$$
I have $\pu{1000 grams}$ of $\ce{Sb2S3}$ that reacts with $\pu{10 grams}$ of $\ce{H2}$ in a reactor at $\pu{713 K}$.
...
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1answer
81 views
Does elimination occur when bromonapthalene is reacted with sodium amide in potassium hydroxide?
What should be the product of this reaction? Some books show that an elimination reaction would happen since $\ce{NH2-}$ is a strong enough base to take away a hydrogen on a benzene ring and create a ...
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Passivation of metals in acids
It is commonly taught in chemistry textbooks that metals such as $\ce{Fe, Al, Cr}$ is "passivated" in cold concentrated $\ce{H2SO4}$ and $\ce{HNO3}$ due to them forming oxide films on the ...
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68 views
Does pH gets affected by pressure? [closed]
My attempt- I thought that pH is h+ ion concentration and change in volume will change its equilibrium according to le chatelier's principle .
But I want to know is it correct or it needs some ...
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How are acids in aqueous solution able to react again after reacting with water?
I hope to clear up some confusion I have about acid-base reactions in aqueous solution.
Based on the Bronsted-Lowry definition of acids, I know acids donate protons. In water, a strong acid should ...
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2answers
60 views
Could the pH in the equivalence point of strong acid and strong base titration be greater than 7? [duplicate]
I have HCl and NaOH titration and in the equivalence point I get pH=8.6, but the pH must be 7 in this kind of titration, then why this happen? Does it possible that I don't take enough points in the ...
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1answer
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How to determine the equivalents of OH- in a titration curve
How does one go about determining the equivalents of $\ce{OH-}$ needed for the titration of a weak acid. For example here is the titration curve for Aspartate:
Why is the equivalents for $\mathrm{p}...
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Is sulphonamide group prone to undergo diazotization?
I wonder if it is not a problem that there is another $\ce{-NH2}$ group in the molecule not connected to aromatic ring and if it can get protonated and react with $\ce{HNO2}$ too, in this case the one ...
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Why is salicylic acid less acidic than o- anisic acid? [duplicate]
The Pka of salicylic acid is 2.97 while that of o-anisic acid is 3.73.
Why is the latter less acidic if the order of +M effect states that -OH>-OR which should make the conjugate base less stable?
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1answer
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Why is ethanol more acidic than acetone?
The acidity of a compound is determined by the stability of its conjugate base and the major structure of enolate has a negative charge on the Oxygen atom. Moreover, the negative charge on the O-atom ...
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Decalcifying metal tubes using organic acids
I have a water that is saturated with Calcium Magnesium Carbonate $\ce{CaMg(CO3)_2}$ (Dolomite). This precipitates in particularly metal pipes and whenever the water is heated. Instead of ion exchange ...
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Behavior of amines as acids
I came across this question which asked us to find in which alternative does the amine behave as an acid the most:
In which of the following reactions does the amine behave as an acid
(a) $\ce{(C2H5)...
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Liquid Fire and Unclogging Bathtub - lingering residue
So my mom needed help with a bathtub drain that wasn't performing all that well. She sent me out to the hardware store to get some Drain-o, but they didn't carry that brand. Instead, the young man ...
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1answer
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Why would a mixture of sucrose, propionic acid, sodium formate, and agar turn light blue? What reaction is happening? [closed]
I made 3 mixtures which had 1 M sucrose, 1% w/v agar, .68% v/v propionic acid, and EITHER 0%, 4%, or 13% w/v sodium formate salt.
It was NOT blue at first, but after a couple hours at RT, the 0% ...
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1answer
90 views
How can I prove ascorbic acid degradation with Uv-vis spectroscopy?
I have to prove scientifically why a sodium ascorbate solution in water turns yellowish - reddish over time. I know ascorbic acid is supposed to oxidize into dehydroascorbic acid, and the latter then ...
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Comparing the basicity of heterocyclic amines
Compare the relative basicity of the following amines.
I know that the higher the electron density on the nitrogen the higher will be its basicity. So here’s my take on each option.
(a)The Nitrogen ...
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1answer
68 views
Why does acetate ion react with water? [closed]
When NaCl is added to water, it dissociates into $\rm{Na^+}$ and $\rm{Cl^-}$. The newly formed $\rm{Na^+}$ and $\rm{Cl^-}$ do not react with water.
When $\rm{CH_3COONa}$ (sodium acetate) is added to ...
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Why hydrogen bonding in some acids make them a stronger acid when it is present even before deprotonation?
If we take the example of salicylic acid, hydrogen bonding is present in the acid as follows:
Even after deprotonation, it has intramolecular hydrogen bonding as follows:
My question:
p-...
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The pH of tap water changes with time [closed]
My following questions are related to $\mathrm{pH}$ values in irrigation water in plants.
I got a $\mathrm{pH}$ meter and I am measuring the tap water and I get an value about 8.
My first question: ...
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If -OMe has a small steric size then why does it increase the acidity of 2-methoxybenzoic acid? [duplicate]
I've read OP Tandon's book of GOC which states:
Acidity order of the below-mentioned structures is: ortho- > meta- > benzoic > para- and the reason for the highest acidity of ortho- being ...
