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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2
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1answer
28k views

How to calculate the volume of a sodium hydroxide solution necessary to add to water, to raise the pH to a certain value?

What volume of $\pu{0.300N}\, \ce{NaOH}$ would be needed to bring $\pu{16.0 mL}$ of distilled water that has a $\mathrm{pH}$ of $7.00$ to a new $\mathrm{pH}$ of $12.42$? This is my attempt at a ...
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2answers
4k views

Why are synthetic pH indicators used over natural indicators?

Synthetic indicators seem to be exclusively used when determining the pH of a substance with an indicator (with the exception of that school experiment where you boil cabbage to demonstrate natural pH ...
2
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0answers
53 views

Comparing basic strength of phosphorus trichloride and phosphorus trifluoride

I need to compare the Lewis basic strength of trihalides of phosphorus My thoughts : Since fluorine is more electronegative, the percentage of $\mathrm s$-character in $\ce{P-F}$ bonds will be lower, ...
-1
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1answer
49 views

Acids and Bases (Spectator Ions Identification)

In an acid reaction with water, or other solvents, how do we know which atom(s) from a compound reacted with that solvent are the spectator ions? Are they the ones soluble in the solvent? Is the way ...
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0answers
41 views

Writing water as a reactant in acid/base dissociation (Brønsted Lowry)?

The dissociation of $\ce{HCl}$ in water is written as: $$\ce{HCl (aq) -> H+ (aq) + Cl- (aq)} \tag{1}$$ Sometimes we also include $\ce{H2O}$ as a reactant to stress the fact that the protons are not ...
3
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1answer
103 views

Is there any diprotoic acid where both pka's are less than 0?

The question states it all. I'm working out special cases for a different problem and such an acid would create another special case. Sulfuric Acid is the strongest that I remember. pKa's −3, 1.99
5
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1answer
206 views

Identifying nucleophiles and electrophiles in an acid-base reaction

Is ammonia a nucleophile and hydrogen the electrophile in the Brønsted-Lowry acid-base reaction of acetic acid with ammonia? $$\ce{CH3COOH + NH3 <=> CH3COO- + NH4+}$$ I say that ammonia is the ...
-2
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3answers
95 views

The Curious Case of the equivalent weight

Please read the reference points given at the end. I understand the following about equivalent weight. Firstly it is given by, $Equivalent\:Weight= \frac{Molar\:Weight}{Valence\:Factor}$ And secondly, ...
-2
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2answers
155 views

Why is sodium bicarbonate added to lower the pH? [closed]

I use salicylaldehyde, chloroacetic acid and sodium hydroxide for the synthesis of o-formylphenoxyacetic acid. In the procedure it is written that after the reaction I need to add sodium bicarbonate ...
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0answers
36 views

Arrhenius acids and bases

According to the Arrhenius definition of acids: An Arrhenius acid is any species that increases the concentration of hydrogen ions in its aqueous solution. Hydrogen Chloride gas ionises in water to ...
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0answers
19 views

IUPAC salt definition makes bases be classified as salts? [duplicate]

The IUPAC salt definition is: "A chemical compound consisting of an assembly of cations and anions" (Compendium of Chemical Terminology Gold Book, Version 2.2.3, 2014) So it means that a ...
3
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1answer
160 views

Finding pH after dilution of acetic acid

We have $\pu{10 L}$ of solution of $\ce{CH3COONa}$ with concentration $C = \pu{1 M}$ and $\mathrm{pH} = 10$. Then we add $\pu{90 L}$ $\ce{H2O}$. What will be the pH of the new solution? My work: \...
5
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2answers
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Comparing Acidic Strength of H3PO4 and H3AsO4

The $\mathrm{p}K_\mathrm{a}$ values for $\ce{H3AsO4}$ and $\ce{H3PO4}$ are $2.30$ and $2.12$ which indicate that $\ce{H3PO4}$ is a stronger acid compared to $\ce{H3AsO4}$. I looked up their ...
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1answer
55 views

Why isn't auto ionisation of water considered when we find the pH during salt hydrolysis?

$\ce{H+}$ concentration from the auto-ionisation of water is $10^{-7}$ If we have $\ce{HA}$ as weak acid and $\ce{BOH}$ as weak base having $\mathrm pK_\mathrm{a} = 3.2$ and $\mathrm pK_\mathrm{b} =3....
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2answers
119 views

Is an aqueous solution of potassium bicarbonate acidic or basic in nature?

The following is the definition of an acid salt according to my textbook: The salts formed by the partial replacement of the replaceable hydrogen atoms (H+ ions) of an acid molecule by a metallic or ...
5
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4answers
2k views

Why does the degree of dissociation change when we dilute a weak acid even though the equilibrium constant is constant?

$K$ represents the ratio of concentrations of molecules in a solution at equilibrium, which means that $Q_\mathrm{r}$ (that ratio at any given point) looks to be identical to $K$. In other words, the ...
2
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2answers
980 views

How to determine the order of acidity of the following dimethyl nitrophenols

This is how I went about it, although I got a wrong answer: 3,5-Dimethyl-4-nitrophenol (2) shows the nitro group to be sterically hindered, due to which it should go out of plane and this will be an ...
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0answers
30 views

Why can't Grignard reagents react like Organolithium does (with acids)?

I'd read yesterday that Grignard reagents can't give ketones on reaction with carboxylic acids. It is because of the fact that Grignard reagent is a "super-base", and it will deprotonate the ...
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4answers
4k views

Why does a buffer work best at the pH closest to its pKa?

I think I'm having trouble understanding exactly how the $\mathrm{p}K_\mathrm{a}$ relates here on a conceptual level. For example I know that carbonic acid works somewhat well as a buffer at $\mathrm{...
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1answer
104 views

Does rate of auto-ionization of water change after adding a strong acid?

We know that a reaction could have different rates at equilibrium. For example, lets take the reaction: $$\ce{A + B -> C }$$ At equilibrium, the rates of formation and dissociation will be equal: $$...
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1answer
362 views

Why is aniline more basic than pyrrole?

In a question asking to compare the basicity of pyrrole and aniline, the explanation given for aniline being more basic than pyrrole was as follows: Basicity depends on the availability of lone pair ...
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2answers
907 views

Does Cl- Have more -I effect or +M effect ( Resonance effect)?

In this question my answer was (A) because i though $\ce{NH2}$ group would give more electrons than $\ce{Cl-}$ . But the correct answer is (D) and my teacher's reason is that chlorine has more ...
36
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2answers
15k views

Why is pyrimidine less basic than pyridine?

From Wikipedia's article on pyrimidine: Because of the decreased basicity compared to pyridine, electrophilic substitution of pyrimidine is less facile. But why is pyrimidine less basic than ...
2
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3answers
6k views

Acid/alkali + salt reaction?

Why some acid/alkali can react with some salt, forming another acid/alkali? For example: $\ce{2NaCl +H2SO4->Na2SO4 + 2HCl}$ $\ce{Ca(OH)2 +Na2CO3->CaCO3 +2NaOH}$ but not the reverse. What ...
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2answers
272 views

Reaction of copper with nitric acid [duplicate]

When copper reacts with dilute nitric acid, $$\ce{3Cu + 8HNO3 -> 3Cu(NO3)2 + 2NO +4H2O}$$ while with concentrated nitric acid, $$\ce{Cu + 4HNO3 -> Cu(NO3)2 + 2NO2 + 2H2O}$$ As we see that with ...
9
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2answers
12k views

Why, in titration, is universal indicator not commonly used?

My teacher said that we always used indicators such as methyl red, methyl orange, litmus, phenolphthalein, etc. rather than universal indicator. I don't understand why, though, would not universal ...
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0answers
19 views

How does concentration of H3O effect the concentration of OH [duplicate]

I know that [H+][OH-] will always equal 10^-14 in 25c water, however, I would like to know why that is, like if there is an extremely small amount of both H+ and OH- in the water how would increasing ...
9
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2answers
7k views

Why is carbonic acid a weaker acid than acetic acid?

Is it because the $\ce{OH}$ group next to $\ce{COOH}$ in carbonic acid donates electron density to the $\ce{COO-}$ by resonance, making it a stronger base, compared to a weaker electron donating ...
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0answers
25 views

How does a change in pH affect the colour of a leuco dye in a thermal paper?

I am investigating the way that a leuco dye is released in thermal paper once heated. I have understood that leuco dyes, when in their colourless state are encapsulated in an acid developer in the ...
3
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0answers
161 views

Why is N,N,2,6-tetramethylaniline less basic than N,N,2-trimethylaniline?

According to me, N,N,2,6-tetramethylaniline should be more basic than N,N,2-trimethylaniline due to more steric inhibition to resonance, but the answer is given opposite. What is the reason for that?
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1answer
942 views

Is the reaction between thiosulfate and hydronium an acid-base reaction?

Is the following reaction an acid-base reaction: $$\ce{2 H3O+(aq) + S2O3^2-(aq) -> 3H2O(l) + SO2(g) + 1/8 S8(s)}$$ And if so, which is the acid and which is the base?
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1answer
84 views

Why does magnesium bromide transfers from a carbon atom to nitrogen in piperidine?

In this reaction, why does $\ce{MgBr}$ goes to the $\ce{>NH}$ group and form a bond with nitrogen by removing $\ce{-H}$. Also where does the negative charge go?
24
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3answers
11k views

The acidity of boric acid

The “real way” boric acid behaves as an acid in water is first by acting as a Lewis acid (bottom reaction, in black). In fairness to the undergrads, I’d bet >25% of graduate students around the ...
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1answer
2k views

Boric Acid - Mechanism of Acidity

I was wondering how one could test the hypothesis that boric acid behaves not as a Brønsted acid but as a Lewis acid in that boric acid cleaves water molecules as to make hydrogen protons. rad Could ...
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0answers
89 views

Reaction between Polyvinylpyrrolidone (PVP) and NaOH

I am using polyvinylpyrrolidone (PVP) as a dispersant in a reaction. The reaction contains concentrated NaOH (pH of the NaOH solution is 12 to which PVP is added). When I add the PVP, the solution ...
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0answers
37 views

Adding acid to hard water to prevent limescale deposition

Acid is commonly used to remove deposited limescale. If I wanted to prevent build-up of limescale in appliances, would it make sense to add acid to the water in the first place if that doesn't harm ...
9
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2answers
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Will using vinegar harm car paint?

After having parked my car in a newly constructed airport parking garage, I came back to find something had dripped through a crack in the ceiling of the structure and left considerably thick film on ...
0
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1answer
53 views

Why don't dicarboxylic acids show hydrogen bonding in spite of the fact that carboxylic acids exist usually as dimers in polar aprotic solvent? [closed]

I have seen several examples: The fact that maleic acid is more soluble in water than fumaric acid in spite of the fact that it must be able to show intramolecular hydrogen bonding. trans-...
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0answers
58 views

Adding a base and a salt to a hydrated complex

The question goes like this: $\ce{Fe(NO3)3}$ V= $\pu{1 liter}$ and $\ce{[Fe(NO3)3]} =\pu{0.1 moles/liter}$. Calculate the $\mathrm{pH}$ of this solution using the values of $K$ given. We add a solid ...
5
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1answer
68 views

Help with idea for an optical pH sensor

I am experimenting at home with the idea of making an optical pH sensor that can read the colour of pH indicator using photodiodes. I am wondering if there is some kind of ion permeable membrane that ...
1
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1answer
328 views

Why do bases taste bitter? [closed]

My chemistry teacher told us that acids taste sour and bases taste bitter. After reading Do acids without hydrogen taste sour? and https://en.wikipedia.org/wiki/Taste#Sourness I learned that sourness ...
7
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2answers
2k views

Which salt will best be able to buffer the addition of HCl?

From these three salts, which will be best able to buffer the addition of $\ce{HCl}$? ammonium chloride sodium carbonate ammonium acetate. I think sodium carbonate is the right choice because when ...
1
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2answers
805 views

Negative hyperconjugation

Compare the acidity of the following compounds: $\ce{CF3OH}$ and $\ce{CCl3OH}$. My attempt: according to me $\ce{CCl3}$ group will show a stronger Negative hyperconjugation effect than $\ce{CF3}$, ...
3
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1answer
2k views

Acidity of aldehydes and ketones and enolate formation

In most academic courses you'd learn that aldehydes are more acidic (lower $\text{p}K_\text{a}$) than ketones due to the lower electron donating effect of the proton compared to the alkyl group of the ...
2
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3answers
116 views

White snow-like powder below sodium hydroxide solution [closed]

I have created sodium hydroxide solution with half cell brine electrolysis but, finally I got white snow-like insoluble powder sank below sodium hydroxide. What should I do keep or remove it?
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2answers
79 views

Aspartic acid conjugate base acidity

Question Which hydrogen among the four in the conjugate base of aspartic acid is most acidic? Answer My attempt I am confused between Hb and Hc I know Hd has $\mathrm pK_\mathrm a \approx 9$, so ...
8
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2answers
683 views

Why is 4-hydroxypyridine more acidic than benzoic acid?

4-hydroxypyridine (or 4-pyridone) has a $\mathrm{p}K_\mathrm{a}$ in the ballpark of $3$ to $3.33\:^1$ (in the pdf linked below, the $\mathrm{p}K_\mathrm{a}$ of 1-methyl-4-pyridone has been given to be ...
0
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1answer
338 views

Why sugar solution/sugarcane juice becomes sour when kept for certain time?

I stir-dissolve some sugar in a cup of water and then keep it open for certain time (say a few hours), when I taste it I feel that it has became sour. I have observed the same thing many times when I ...
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1answer
65 views

Comparison of basicity of o-phenanthroline and ammonia

I was trying to compare the basicity of o-phenanthroline and ammonia. According to me, the factors that are seen in o-phenanthroline are: o-Phenanthroline has two nitrogen atoms at the 1,10 positions....
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0answers
22 views

Can the inner amine groups of Bacteriopheophorbide A become positively charged in aqueous solutions without the use of very strong acids?

In an attempt to calculate the pKa of the carboxylic acid group of Bacteriopheophorbide A (BPheo, Pubchem), I generated the structure in MarvinSketch (ChemAxon product) and I came across an ...

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