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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Reference for Hammett acidities of dilute H2SO4?
When $\ce{H2SO4}$ is dissolved in water in little amounts ($<\pu{1M}$), the $\mathrm{pH}$ scale can be used to measure the acidity of the solution. However, in larger concentrations, this breaks ...
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1answer
21 views
Contradictions in acidity and solubility of phenol derivatives
o-Nitrophenol is less acidic in comparison to p-nitrophenol due to intramolecular hydrogen bonding. This effect also is the reason for o-nitrophenol being less soluble in water.
At the same time, ...
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2answers
58 views
Deprotonated form of phenolphthalein
The wikipedia page states clearly that the coloured form of phenolphthalein is the one with two protons removed. What is the evidence that phenolphthalein loses both protons in basic solution? And ...
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16 views
How are the pKa's of very strong acids derived mathematically?
It is often said that "for very strong acids (HCl, H2SO4, etc.), the pKa value cannot be experimentally derived from standard titration and instead needs to be theoretically computed". However, I ...
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35 views
Is Anhydrous Sulfuric Acid Really Impossible?
I was reading the wikipedia article for Sulfuric acid, and came across the following table:
I realize that this species is highly self protonating, and assuming this data to be experimentally ...
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1answer
39 views
Estimation of Sodium Hydroxide
Why is estimation of sodium hydroxide more accurate with oxalic acid rather than with sulfuric acid or any other strong acid?
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14 views
How ion size/electronegativity influences strength of an acid
My prof was explaining how we can use the structure of acids and bases to rationalize relative strengths (ie: acid X is stronger than acid Y because ...). He then went on to explain how when ...
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30 views
Is OH– a weak base or a strong base? [closed]
From my point of view, $\ce{OH–}$ should have been a very good base, but in my copy, it is written that $\ce{OH–}$ is a weak base. All the articles that I can find on the internet do nothing but ...
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1answer
35 views
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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1answer
57 views
Validity of the leveling effect of water in nitration reactions
Wikipedia gives this as the levelling effect of water
Any acid that is stronger than $\ce{H3O+}$ reacts with $\ce{H2O}$ to form $\ce{H3O+}$. Therefore, no acid stronger than $\ce{H3O+}$ exists in $\...
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1answer
91 views
Do amphoteric cations exist?
I know that anions such as $\ce{CH3COO-}, \ce{OH-}, \ce{CN-}$ are basic in nature, since they are conjugate bases of weak acids. Similarly, cations such as $\ce{NH4+}, \ce{H3O+}$ are acidic in nature ,...
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143 views
Which one is the strongest base among the following compounds?
I am confused between option (2) and (4). Both lone pairs of nitrogen are localized, so next, I looked at the hybridization of $\ce{N}$ in each compound. As in (2), the $\ce{N}$ is $\mathrm{sp^2}$ ...
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2k views
Neutralizing a sulfuric acid spill
From my AP Chem Prep Book:
What should you do if you spill sulfuric acid on the countertop?
A) Neutralize the acid with vinegar.
B) Sprinkle solid NaOH on the spill.
C) Neutralize the acid ...
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1answer
95 views
Lewis acidity comparison of boron and aluminium trichlorides
Lewis acidity is a function of electron deficiency on the acceptor atom, which in this case is $\ce{B}$ and $\ce{Al}$ respectively.
Back donation is better as is the case of $\ce{B}$, due to better ...
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3answers
28 views
Is acidic character related to reducing power?
My book says that the acidic character of halogen acids increases on going down the group because the bond strength decreases, making it easier to release the $\ce{H+}$.
But I also know that $\ce{HI}$...
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1answer
40 views
Why is high molar molar mass a requirement of good primary standards for volumetric analysis? [closed]
I have been taught that using primary standards with a relatively high molar mass will reduce the error between the equivalence point and the end point during titration. However, I am unsure as to why ...
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2answers
64 views
Lithium oxide is a base, but lithium alone is not. Why? [closed]
When lithium oxide reacts with water, it is said to be a base:
$$\ce{Li2O + H2O -> 2 LiOH + H2}$$
When lithium metal reacts with water, it is not considered a base:
$$\ce{2 Li + 2 H2O -> 2 ...
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13 views
measuring the pKa of acetic acid in mixtures of water and methanol(changing percentage)
My goal is to measure the pKa of acetic acid in different mixtures of water and methanol, in which the proportion by weight of methanol will be changed. How can I measure the pH of this solution? Is ...
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1answer
34 views
Finding Ka of a monoprotic weak acid from pH and concentration of added sodium salt
A solution of $\pu{0.36 M}$ of the sodium salt of a generic monoprotic weak acid $\ce{HA}$ has a $\mathrm{pH}$ value of $8.782.$ $K_\mathrm{a} = ?$
Why doesn't the following formula work in this ...
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2answers
382 views
How does ammonium chloride increase the solubility of magnesium hydroxide in water?
In my textbook it is written that $\ce{Mg(OH)2}$ is slightly soluble in water, and it forms a milky solution which is called "milk of magnesia".
Its solubility can be increased by the addition of $\...
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1answer
46 views
Can ascorbic acid be neutralized and keep it's elastic properties in dough?
Ascorbic acid (C6H8O6) is commonly used in dough to give it strength and elasticity. However, I need this dough to be alkaline, or at the very least neutral. I've used sodium carbonate (Na2CO3) before ...
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52 views
pH of amphoteric species
For a solution of $\ce{HA-}$, I have seen the following approximations for the $\mathrm{pH}:$
$$\mathrm{pH} = \frac{1}{2}(\mathrm{p}K_\mathrm{a1} + \mathrm{p}K_\mathrm{a2})\tag{1}$$
$$\mathrm{pH} = \...
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3answers
68 views
Tap water pH adjustment using citric acid
I've lowered tap water pH from 7 to 6 using citric acid. After couple of hours pH raised again to 7.
What is the reason for this raise? Citric acid overcomes waters buffering feature then raise the $...
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91 views
How to simplify these system of equilibrium equations
What is the pH when $0.025$ mol $\ce{NiCl2}$ is added to $\pu{1.00 L}$ of a $\pu{0.100 M}$ solution of $\ce{HCN}$, if the formation constant for $\ce{Ni(CN)4^2-}$ is $K_f=\pu{1.0e22}$, and the $K_a$ ...
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2answers
67 views
Acidic nature of boric acid when its concentration high
Following statement was given for boric acid $(\ce{H3BO3}):$
At low concentrations $(\leq\pu{0.02 M})$ essentially $\ce{B(OH)3}$ and $\ce{B(OH)4-}$ are present, but at higher concentration the ...
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1answer
23 views
Limiting fraction of association
Show that the limiting fraction of association of a base in water, as
the concentration of base approaches 0, is $$\alpha=\frac{10^7 K_b}{(1+10^7\times K_\mathrm{b})}.$$
I have tried this problem ...
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1answer
56 views
Why there is a huge difference between the basicity of urea and guanidine?
The two molecules have very similar structures, but urea has a $\mathrm{p}K_\mathrm{b}$ of $13.9,$ while guanidine have a $\mathrm{p}K_\mathrm{b}$ of $0.4.$ If guanidine cation can be stabilized by ...
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21 views
∆G° and ∆G°' for acid dissociation
For the dissociation of an acid AH, where $\ce{AH <=> A- + H+}$, if $∆G°$ is $\pu{+25 kJmol-1}$ at $\pu{300 K}$, what is $∆G°'$? I know that for $∆G°$, $\ce{[H+]}$ is $\pu{1M}$, whereas for $∆G°'...
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What is the order of acidity for hydrogens in primary, secondary and tertiary alkanes, alkenes, and cycloalkanes [duplicate]
The bond dissociation energies of C-H bonds in alkanes, alkenes and aromatic compounds decrease in the following order: primary > secondary > tertiary > allylic > benzylic.
The weaker the bond, the ...
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22 views
Pyridinium ion in inositol nicotinate
I have read about inositol nicotinate which is used as a medication for deficiency in vitamin B-3. I think that if acetic acid was applied to this medication it would form pyridinium ion and acetate ...
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1answer
27 views
Does reaction of alkali and alkaine earth metals' reaction with water an acid-base reaction? [closed]
In my chemistry notes the teacher gave me the note that reaction of alkali, alkaline earh metals' reactivity with water, acids(e.g. H2S) increases down the group and bases(e.g.NH3) decreases down the ...
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1answer
35 views
Comparing basic strength order of amines
In the above question I was asked to compare the basic strength order.
So I did it like this:
The Nitrogen in I and II will not participate in resonance so the only effect it could produce is ...
5
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1answer
200 views
Examples of Lewis base nature of sulfur dioxide
I have read that sulfur dioxide acts as both Lewis base (due to presence of lone pair over $\ce{S}$ and/or $\ce{O})$ and Lewis acid (due to presence of vacant d orbital). I found many examples of $\ce{...
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Acidity comparison on R-PO3H2
Question
Compare the acidity $(K_\mathrm{a1})$ of the following three acids:
$\ce{H3PO4},$ $\ce{Ph-PO(OH)2}$ and $\ce{H3C-PO(OH)2}.$
Thoughts
These three acids are of type $\ce{R-PO3H2},$ where ...
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1answer
33 views
Does clove oil/eugenol interact with nylon type plastics?
So I am aware that the eugenol in clove oil readily melts #6 type plastic (polystyrene). Polypropylene has a higher resistance, while HDPE type plastics seem to have the highest resistance.
My main ...
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50 views
Difference between neutral and amphoteric oxides
What is actual difference between neutral oxides (e.g. $\ce{NO},$ $\ce{N2O},$ $\ce{CO})$ and amphoteric oxides (e.g. $\ce{Al2O3})?$ I got a hint of it from the comment of Ivan Neretin.
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83 views
Does aniline react with FeBr₃?
I have read that aniline does not undergo Friedel–Crafts reaction because it complexes with Lewis acid $\ce{AlCl3}.$ Will it also react with $\ce{FeBr3}$ during bromination (to receive a 3-bromo ...
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33 views
Why are alkali metal compounds like sodium hydride or sodium amide strong bases but weak nucleophiles?
I understand why compounds such as $\ce{NaH}$ or $\ce{NaNH2}$ are weak nucleophiles: as they aren't very soluble in organic solvents, they react only on the clusters' surface. But why are they strong ...
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1answer
68 views
Easy way to make carbonic acid from other chemicals? [closed]
I would like to test for the reaction between carbonic acid and copper (to simulate the effect of acid rain on copper). However, I find that many supplies failed to provide carbonic acid (either in ...
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1answer
37 views
Why is CO2 more likely to dissolve in a basic solution than an acidic solution? [closed]
I'm having trouble thinking through this problem. I know that when $\ce{CO2}$ dissolves in water it can release $\ce{HCO3-}$ and $\ce{H+}$ and cause a drop in pH. But can I use this to justify why $\...
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21 views
Is it feasible to measure the pH of solution consisting of hydrofluoric acid, methanol and water using redox potential method?
Is it feasible to measure the pH of $\ce{HF}:\ce{H3COH}:\ce{H2O}$ solution using redox potential method?
Can I use this method to calculate the $\ce{H+}$ ions in this solution and specifically, can I ...
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1answer
118 views
Equivalence point vs inflection point in the titration curve of a weak acid
Let's suppose we want to titrate a solution containing an unknown monoprotic and weak acid. We use a strong base, such as $\ce{NaOH}$. When the number (and moles) of hydroxide ions coming directly ...
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1answer
25 views
Ligand substitution reaction in coordination compounds
I know that the following substitution reaction can take place:
$$\ce{[Cu(H2O)4]^2+ (aq) + 4NH3 (aq) -> [Cu(NH3)4]^2+ (aq) + 4H2O (l)}$$
This is because ammonia is a stronger ligand than water.
...
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2answers
135 views
Does H3CO3+ ion exist and what is its structure? [closed]
Why doesn't $\ce{H3CO3+}$ ion exist and why doesn't the carbonyl group in carbonic acid $(\ce{H2CO3})$ seem reactive?
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1answer
31 views
Can hydrogen peroxide be considered an alkali? [closed]
Hydrogen peroxide is miscible with water, can neutralize acids, and produces H2O, but I've never seen it labeled as an alkali, could we still consider hydrogen peroxide an alkali?
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40 views
Is contribution to pH by an acid or base always greater than salt hydrolysis?
I was solving a titration question and the reaction I came to was this:
$$
\begin{array}{lcccc}
\ce{&BOH(aq) &+ &HCl(aq) -> &BC(aq) &+ &H2O(l) }\\
\text{Initial} & x &...
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28 views
Acidity of 2-sulfopropanedioic acid in water
Sulfuric acid is a strong acid ($\mathrm{p}K_\mathrm{a}$ value below that of $\ce{H3O+}$: completely dissociated in water) at its first deprotonation, but is a weak acid ($\mathrm{p}K_\mathrm{a}$ ...
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1answer
157 views
Why is Aluminium oxide amphoteric?
I was reading my book, in which it mentioned that aluminium and gallium oxides are amphoteric and and Indium and thalium oxide are basic in their properties.
But no explanation was given.
Edit:
My ...
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1answer
174 views
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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3answers
128 views
Acidity order of o-nitrophenol vs. o-chlorophenol [closed]
It is given that the above statement is true. Why does o-nitrophenol, in spite of intramolecular hydrogen bonding, have a lower $\mathrm{p}K_\mathrm{a}$ than o-chlorophenol?
