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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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165 views

Finding pH of tri-protic acid

I am studying for my final and I am given this problem: A solution of sodium phosphate is made from 10.5 g sodium phosphate in 150 mL of water. What is the pH of this solution Given: Ka1, Ka2. ...
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2answers
624 views

NaHCO3 required to raise pH of weak HCl solution from 3.5 to 7.2 (doubting my calculations)

I'm a dentist, working on a medical device that will make shots at the dentist office hurt a lot less. The device mixes a drug (2% Lidocaine) that has been acidified with $\ce{HCl}$ to pH 3.5 for ...
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2answers
11k views

MaVa = MbVb - Limitations and Uses

We know that for strong acids with a $1:1$ mole ratio between all particles involved are suitable for use with the aforementioned formula for titration problems. I want to know the limits on this ...
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2answers
133 views

calculating pH - is my answer correct?

I'am working on this exercice, Is my answer correct? and can you please help me to solve the second part? exercice: 1/Calculate the ionization coefficient and pH (with two methods) of a 0.1M ...
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1answer
454 views

Hydrolysis of salt

The hydrolysis of salt tells you whether a salt is acidic or basic. But it does not tell you how acidic or basic a salt is. Is there a way to determine this? My guess is that taking of the weak base ...
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0answers
710 views

Why is H3PO2 more acidic than H3PO4? [duplicate]

Please explain why $\ce{H3PO2}$ is more acidic than $\ce{H3PO4}$.
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1answer
8k views

Basicity of heterocyclic compounds

Pyrrol, furan or thiophene don't have any bond pair electrons free to release which is why they shouldn't be basic, but the lecturer of organic chemistry is saying that they are basic as they react ...
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1answer
122 views

What is the heat of reaction of weak acid reacting with weak base compared to strong acid reacting with strong base? [closed]

My book has this line only that "weak acid and weak base reaction will produce lesser heat than constant enthalpy" of strong acid and strong base neutralization which is $\pu{-57.3 kJ/mol}$.
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1answer
21k views

Titration curve graph, finding exact point of the equivalence point

I plotted all my data points and made this graph in excel. Now I need to find the volume of titrant required to read the equivalence point, as well as the pH after 18.5 mL of titrant have been added. ...
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1answer
286 views

Q. 36 2018 molar solubility of CaF2 at pH3 given molar solubility at pH7 and pKa of HF [closed]

This is Q36 on the 2018 Chemistry Olympiad: Calcium fluoride, $\ce{CaF2}$, has a molar solubility of $\pu{2.1e–4 mol L–1}$ at pH = 7.00. By what factor does its molar solubility increase in a ...
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12k 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 ...
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Why concentrated sulfuric acid for dehydration and dilute for hydration?

To dehydrate ethanol one uses concentrated sulfuric acid: $$\ce{C2H5OH ->[\text{conc.} H2SO4] C2H4 + H2O}$$ but to go in the reverse direction, dilute sulfuric acid is used: $$\ce{C2H4 + H2O -&...
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1answer
2k views

Why is proton transfer so fast?

Why is proton transfer always kinetically favored? In other words, why are Brønsted acid-base reactions so quick? Is it because protons are generally unhindered, sterically? This seems plausible; ...
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1answer
25k views

How does sodium bicarbonate act as a deodorizing agent?

I was reading this other question on the site: Deodorizing using baking powder instead of baking soda. Apparently, baking soda is used quite often as a cleaning and deodorizing agent. From what I ...
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2answers
6k views

Chemical compounds responsible for the colors in flowers?

I know that anthocyanins are a class of compounds responsible for the purple colors found in flower petals. Anthocyanins (also anthocyans; from Greek: ἀνθός (anthos) = flower + κυανός (kyanos) = ...
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15k views

Why doesn't HCl form when you dissolve NaCl in water?

People say it dissolves, but shouldn't the acid form? $$ \ce{NaCl + H2O ->[?] HCl + ???} $$
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14k views

How to separate HCl and NaOH from salt and water solution?

I mean, how can we reverse the neutralization reaction of $\ce{HCl}$ and $\ce{NaOH}$ to get back $\ce{HCl}$ and $\ce{NaOH}$. I want to extract $\ce{HCl}$ and $\ce{NaOH}$ from a mixture of common salt ...
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How does the HCl-KCl Buffer work?

I have just been studying the $\ce{HCl}$-$\ce{KCl}$ 'buffer', but there are still quite a few things I am uncertain about. I would appreciate any help in clearing up some questions I have. What I ...
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17k views

Why formulate drugs as HCl salts when HCl is in stomach acid?

I know there are issues of formulation and industrial processing that make it advantageous to produce many amine containing drugs as their salts rather than as freebases. And if giving the drug ...
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5answers
15k views

Is there such a thing as an acid without a hydrogen?

I'm in AP Chemistry and we are learning about the Brønsted-Lowry model and my teacher mentioned that "for the most part" acids have hydrogen, could there be such a thing as an acid that has no ...
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2answers
934 views

Mechanism of a dephenylation reaction

I recently came across this reaction in my undergraduate labs. The experiment is taken from this article: J. Chem. Educ., 2008, 85, 413. The condensation of 2-methoxynaphthalene with cinnamoyl ...
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26k views

Why is nitric acid such a strong oxidizing agent?

In my teaching-lab experiments I've seen that nitric acid solutions are able to facilitate the dissolution of metals such as silver, even though they are more active than hydrogen. Does anyone know ...
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3answers
75k views

What makes Coke acidic?

What makes Coke and other soft drinks acidic? These drinks are carbonated, so a freshly-opened can should have a lot of dissolved carbonic acid, but the ingredients also lists phosphoric acid. Would ...
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1answer
12k views

Basicity Alteration Due To Ortho Effect In Methoxy Aniline System

I wanted to ask something more in reference to this question Ortho-effect in substituted aromatic acids and bases Suppose instead of toluidine, 2-methoxyaniline and 3-methoxyaniline are present. Now ...
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15k views

Why are acetals stable to bases and nucleophiles?

Why are acetals stable to bases and nucleophiles? Could it be due to electronic effects? Lone pairs on the two oxygen atoms create an unfavorable environment for the approaching nucleophiles and ...
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1answer
28k views

Condition For NaHCO3 to react to form CO2 with organic acids

My professor told us the following: $\ce{NaHCO3}$ will react to evolve $\ce{CO2}$ whenever the acidic nature of the reactant exceeds the acidic nature of benzoic acid. I want to know why this ...
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1answer
35k views

Does dilution of a buffer affect pH?

The Henderson-Hasselbalch equation for the $\mathrm{pH}$ of a buffer solution of the monoprotic acid $\ce{HA}$ is given by $$\mathrm{pH}=\mathrm pK_\mathrm a+\log{\frac{[\ce{A-}]}{[\ce{HA}]}}$$ Since ...
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2answers
10k views

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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1answer
6k views

Why is HClO4 the strongest oxyacid?

Why is $\ce{HClO4}$ the strongest oxyacid? My effort: The structure of $\ce{HClO4}$ should be tetrahedral. So when there is a negative charge on oxygen, it should not be in resonance with other ...
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2answers
10k 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
30k views

How does adding lemon juice to sugar make better caramel?

It's a common cooking advice: if you want a somewhat softer caramel, add some lemon juice to the sugar: To help prevent the caramel from crystallizing, you can add an acid to the sugar before you ...
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3k views

Difference between Sildenafil and Sildenafil citrate

The data I found seems to show no difference between Sildenafil and Sildenafil citrate. But if they are the same things, why Pfizer use Sildenafil citrate instead of Sildenafil as their product Viagra?...
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1answer
292 views

By how many pKa units will the pKa value of a ketone be minimized by addition of a Lewis acid

I want to enolize a ketone, for instance acetone with a $\mathrm{p}K_\mathrm{a}$ value of about 20 (in $\ce{H2O}$). I'd like to know if there exists a rule of thumb to predict how the $\mathrm{p}K_\...
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1answer
3k views

Most basic nitrogen in Adenine

I need to find the most basic site of Adenine: The $\ce{NH2}$ group and $\ce{NH}$ cant be strong base as electrons are delocalised. This leaves us with $1,7,3$. I thought that electron density on $1,...
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2answers
13k views

Which will be the most acidic hydrogen in the following organic compounds?

Which will be the most acidic hydrogen in both cases? Please explain. According to me, in the first compound 2 should be most acidic as in both 1 and 2, resonance occurs but 2’s carbon is closer to ...
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2answers
5k views

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 ...
7
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2answers
6k views

Is steric inhibition of resonance or steric inhibition of protonation dominant in o-toluidine?

I wish to know which effect out of steric inhibition of resonance (SIR) or steric inhibition of protonation (SIP) is dominant over the other when comparing basicities of o-toluidine and aniline: ...
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2answers
4k views

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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3answers
4k views

Is the Henderson–Hasselbalch equation volume independent?

Looking at this equation $\mathrm{pH} = \mathrm{p}K_\text{a} +\log\frac{[\ce{CB}]}{[\ce{A}]}$ makes me think that it is concentration independent. What I mean is, when we look at $\frac{[\ce{CB}]}{[\...
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4answers
33k views

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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1k views

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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2k views

Selecting between redox and neutralization reactions for a mixture of HCl, H2SO4 and NaOH

I know that you can have 2 acids reacting with 1 base. These 4 reactions are an example of this: $\ce{3 HCl + H2SO4 + NaOH -> 3 H2O + SCl2 + O2 + NaCl}$ $\ce{6 HCl + 4 H2SO4 + 2 NaOH -> 8 H2O ...
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1answer
1k views

Can the colour change in litmus paper be explained by conjugated systems?

I have been trying to understand the colour change in litmus paper on a more detailed level than "the chemical identity changes, and therefore also physical properties". I have knowledge of the ...
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1answer
1k views

Which is more acidic BF3 or AlCl3?

Which of the species $\ce{BF3}$ and $\ce{AlCl3}$ is more acidic, both are electron deficient. In case of $\ce{BF3}$ one can argue that there is extensive p-π-p-π back bonding and as a result ...
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2answers
3k views

Why doesn't a buffer solution change ph(Appreciably?)

Consider a buffer solution containing weak acid $\ce{CH3COOH}$ and its salt $\ce{CH3COONa}$: \begin{align} \ce{CH3COOH &<=> CH3COO- + H+} \tag{1}\\ \ce{CH3COONa &-> CH3COO- + Na+} \...
15
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1answer
3k views

Determining the pH of an organic solvent

Our work is faced with the issue of determining the charge of compounds that are dissolved in chloroform. One could realistically determine the charge of the relevant moieties knowing the $\mathrm{p}...
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3answers
9k views

Why isn't dry CaCl₂ used to dry HCl gas instead of concentrated sulfuric acid?

In our chemistry books, it is said that concentrated sulphuric acid is used to dry $\ce{HCl}$ gas. But, concentrated sulphuric acid is a strong oxidising agent so, why isn't $\ce{HCl}$ gas oxidised ...
13
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5answers
15k views

Why isn't water acidic?

The definition of an acid is a compound with a hydrogen cation and a non-metal anion. Water is a hydroxide bonded to a hydrogen atom. This hydroxide has a net negative charge, too, since the negative ...
12
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3answers
89k views

How do I calculate the degree of dissociation in equilibrium?

In my textbook, for calculating the percentage dissociation of $\ce{HF}$ for the given equation: $$\ce{HF + H2O <=> H3O+ + F-}$$ The solution is: Initial Concentrations $$[\ce{HF}] = 0.08~\...
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2answers
9k views

Which is more basic, hydrazine or ammonia?

Which of the following will be more basic, hydrazine $\ce{H2N-NH2}$ or ammonia $\ce{NH3}$? My chemistry teacher said that $\ce{NH3}$ is more basic since after giving $\ce{H+}$ to hydrazine results in ...