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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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Mass-Charge balance equations

How to write mass balance equations and charge balance equations of the solution composed of $\pu{0.1M}\text{ }\ce{ NaH2PO4}~ \text{and}~\pu{0.05M}\text{ }\ce{ Na2HPO4}$? After writing the equilibria ...
37
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2answers
4k views

Why is arsenous acid denoted H3AsO3?

Inspired by this question, I'm wondering why arsenous acid is frequently denoted $\ce{H3AsO3}$, as opposed to $\ce{As(OH)3}$, which would appear to more accurately reflect its connectivity? [edit] I ...
4
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1answer
2k views

Why is sulfuric acid used in the Jones oxidation of alcohols?

When oxidising primary alcohols, $\ce{K2Cr2O7}$ is used because it's a useful & readily available oxidising agent. Why does the sulfuric acid need to be added? Does it have to do with the ...
2
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1answer
23 views

How does monoethanolamine (MEA) increase pH?

I know pH of a solution increases with increase concentration of $\ce{OH-}$. I'm wondering: when adding MEA, is the $\ce{OH-}$ group from the MEA breaking off, or is it the whole MEA molecule taking ...
6
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1answer
772 views

Zwitterion (amino acid) equilibrium and the equilibrium constant

I just had my biology test paper back from my teacher, and my teacher insisted that when functioning as a buffer in an alkaline solution, the amino acid deprotonates by the ammonium group instead of ...
6
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2answers
364 views

How is the trend of acidity in the sequence: phosphinic, phosphonic, phosphoric acid explained?

How is the trend of increasing $\mathrm{p}K_\mathrm{a}(1)$ value in the sequence: phosphinic $(1.24)$, phosphonic $(2.00)$, phosphoric acid $(2.21)$ explained (the image was taken from Housecroft ...
2
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1answer
33 views

Does hyperconjugation into sigma-star explain methylamine's increased basicity relative to ammonia?

The inductive effect with the polarisation of the C-N bond obviously plays a role in stabilising the positive charge of the conjugate acid. But given the similar electronegativities for C and H, CH3 ...
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1answer
470 views

Applying Henderson–Hasselbalch equation to amino acids: which pKa to use to calculate Z-/HZ ratio?

I was wondering which $\mathrm{p}K_\mathrm{a}$ to use when calculating the ratio of $\ce{HZ}$ to $\ce{Z-}$ of amino acids, the Henderson–Hasselbalch formula used: $$\mathrm{pH} = \mathrm{p}K_\text{a} ...
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31 views

Hydrofluoric acid in the body causing a acidic blood [on hold]

Jet fuel splashed on person and hydrofluoric acid seeped in and targeted calcium in pelivis and feet. How would you treat it
4
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4answers
167 views

Why does the degree of dissociation change when we dilute a weak acid even though the equilibrium constant $K$ 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 ...
1
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1answer
34 views

Identifying Lewis acid

What is the Lewis acid on the reactants side? $$\ce{HNO2(aq) + HPO4^{2-}(aq) <=> NO2-(aq) + H2PO4-(aq)}$$ The book says it is the $\ce{H+}$ only, not the whole molecule of the nitrous acid, ...
3
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1answer
53 views

Comparison of acidities

My book says To compare the acidities of two compounds, compare the stability of the anions formed by loss of a proton with respect to the original compound. Suppose we have acetic acid and ethyl ...
2
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2answers
5k views

Mixing hydrochloric acid and sulphuric acid, both concentrated

In the chemistry lab, I stupidly decided to mix hydrochloric acid and sulphuric acid, both concentrated, in a random ratio, which was about $\pu{50 ml}$. When I poured them in one test tube, the ...
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1answer
69 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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0answers
41 views

When is an organic phosphate acid and when is it not? [on hold]

I would like to know when an organic phosphate is acid and when it is basic. I think I need the acidity constant given by the equilibrium equation in aqueous environment. I tried to find the ...
2
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3answers
539 views

How can I understand the Lewis acid-base interaction of iron(III) and water?

The interaction between $\ce{H+}$ and $\ce{NH3}$ as respectively a Lewis acid and a Lewis base is clear for me. $\ce{NH3}$ has a lone electron pair and $\ce{H+}$ has no electrons, or, saying politely, ...
3
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2answers
1k views

Can hydrofluoric acid etch glass at a pH of 7.0?

Will it still etch glass when very dilute? Will the reaction still proceed slowly? At what pH will the reaction stop completely? From Wikipedia on hydrogen fluoride: "Although hydrofluoric acid is ...
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1answer
59 views

Why is a negatively charged atom less likely to hydrogen bond than a neutral atom?

Can someone explain why a negatively charged atom let's say $\ce{CH3SH}$ is less likely to bond with an additional hydrogen than $\ce{CH3S-}$? And can anyone relate this to nucleophilicity in a ...
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1answer
9k views

Why are limes alkaline, but lemons are acidic? They taste about the same [closed]

So, this is kinda a dumb question, but I'm curious. Both are citrus fruits and very related to each other and taste sour which corresponds to both being acidic. Why then are limes said to be alkaline, ...
4
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3answers
15k views

Why does electronegativity create a stronger acid, but so does greater electron distribution?

I just learned that: Acids get stronger with: Increasing electronegativity of atom bonded to $\ce{H}$. Size of atom bearing negative charge. Hybridization of negative charge (more s character, $\ce{...
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0answers
20 views

How can I remove iron oxide from acidic solution? [on hold]

I do some experiment for chemical treatment on dyeing sludge with iron sulphate. This chemical removes dye with chelating with dye. pH of sludge is 12 and after treat with iron sulphate decrease till ...
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1answer
44 views

Titration of 0.2 M KOH with 0.05 M HCl [closed]

I need to use the following example to calculate the acid base reaction for the titration of $\pu{0.2 M}\; \ce{KOH}$ 0.2 N with $\pu{0.05 M}\; \ce{HCl}$ 0.05 N of a sample that produces $\ce{CO2}$. ...
23
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3answers
149k views

How does one tell if a specific molecule is acidic or basic?

Let's take the $\ce{KOH}$ molecule into account. I know it is a base from literature, but how would one go about determining if a molecule is acidic or basic simply based on the structure of the ...
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0answers
452 views

Calculating the pH of buffer solution made of two salts of a polyprotic acid

When we are making a buffer solution by solutions of a weak acid and its salt like $\ce{CH3COOH}$ and $\ce{CH3COONa}$, or by a weak base and its salt like $\ce{NH3}$ and $\ce{NH4Cl}$, we can use the ...
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1answer
57 views

pH of very dilute acids

From doing some research on the site I have found that many people have posted about solutions of $\ce{HCl}$ where $[\ce{HCl}] = \pu{1e-8 mol dm-3}$ Here they are able to deduce $$[\ce{H+}] = \frac{[...
3
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1answer
93 views

Identifying unknown solution with indicators. why is one pKa value ignored and how to treat negatives values?

Three test tubes contain an identical solution of unknown pH. The first one is tested with thymolphthalein and turns colourless The second is tested with a-naphtholphthalein and turns blue ...
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0answers
26 views

Solving Polyester but no chromed steel

In short I'm looking for an acid that can solve a polyester, fiberglass composite. However it cannot damage steel. First of all i like to say that i'm not a chemist. I work in a plastic moulding ...
5
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1answer
203 views

Can acid mine drainage form acid rain?

Can acid mine drainage form acid rain? Since normal acid rain is formed via combustion of fossil fuels, the sulphur dioxide and nitrogen dioxide are all in the gas phase, whereas in acid mines the ...
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1answer
26 views

Polyprotic Acid Titrations

Titrating a mixture of strong and weak acids will yield endpoints such that the volume of base required to reach each endpoint will be different for each acid, e.g. in a mixture of HCl and CH3COOH, ...
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1answer
35 views

Lewis acid character

Which will have more lewis acid character out of $\ce{BCl3}$ and $\ce{AlCl3}$ ? My attempt: In $\ce{BCl3}$, the back bonding takes place and there is 3pπ-2pπ overlap and in $\ce{AlCl3}$ it is 3pπ-...
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0answers
108 views

How to calculate concentrations when dissolving two salts?

Some solid silver bromate was dissolved together with solid silver acetate what would be the highest achievable pH? \begin{align} K_\mathrm{sp}(\ce{AgBrO3}) &= 5.38 \times 10^{-5}\\ K_\mathrm{sp}...
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0answers
26 views

Does equilibrium shift (for an acid) mean enhancing its strength? [closed]

Consider the equilibrium reaction of Acetic Acid dissociating into Acetate anions and hydrogen ions. If NaOH is introduced into this system, there are 2 possibilities: 1) The NaOH can react with (...
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2answers
58 views

Why can't a weaker acid protonate the conjugate base of a stronger acid?

So I've heard that, supposedly, a weaker acid cannot protonate the conjugate base of a stronger acid to give that stronger acid. For instance, adding ethanoic acid to sodium sulphate will not result ...
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4answers
46k views

Why is formic acid a stronger acid than acetic acid?

I am told that because the methyl group is electron donating in the conjugate base of acetic acid, this destabilizes the conjugate base by exacerbating the existing negative formal charge on the ...
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0answers
22 views

What are rules for determining pKb and basicity? [closed]

How to solve this $\mathrm{p}K_\mathrm{b}$ and basicity? Arrange the following: In decreasing order of the $\mathrm{p}K_\mathrm{b}$ values: $\ce{C2H5NH2}$, $\ce{C6H5NHCH3}$, $\ce{(C2H5)...
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1answer
6k views

What exactly is basicity?

In my textbook, it’s given that the trend of the basicity of the elements of group 15 is $$\ce{NH3 > PH3 > AsH3 > SbH3 \ge BiH3}$$ Also, it’s said that the reducing character decreases down ...
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1answer
353 views

Writing Mass Balance Equations

I was curious if there is a specific reason why when writing mass balance reactions we always leave a $\ce{H+}$ on the left side of the equation as the professor did not explain so, or is it just ...
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0answers
24 views

Acid rain and the Carbon Dioxide in the atmosphere [closed]

How much $\ce{CO2}$ in the atmosphere has been caused by acid rain's effect on limestones and the like?
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0answers
31 views

Comparing acidity in 3,4-dihydroxyfuran-2(5H)-one and 2,3-dihydroxycyclopent-2-en-1-one

I have two compounds with two hydrogens namely (a),(b),(c) and (d). I have to compare the acidity of the following hydrogens. My approach: I removed the hydrogen atoms one by one and compared the ...
4
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0answers
32 views

Which one is the stronger Lewis base: diethyl ether or tetrahydrofuran?

I am trying to understand Lewis bases (bear with me, I am a physicist). I was asking myself how diethyl ether and tetrahydrofuran compare with respect to their properties as solvents in electrophilic ...
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0answers
22 views

How can the ocean act as a buffer?

I was reading up on the buffering effect of the ocean and I was quite confused about how the buffer is able to do anything. The buffer I will refer to is below: $$\ce{CO3^{-2} +H2O <=> HCO3 + OH^...
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1answer
223 views

In the graph provided, which of the substances is the most efficient in acting as an antacid?

If every dot represents the addition of 0.1 g of the respective base. I suppose that the best would be the one that reaches the highest pH, in the shortest time, for example Calcium Carbonate, but if ...
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2answers
3k views

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 ...
5
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3answers
2k views

Why do you need a strong base for a titration

For a titration, if you want to know the concentration of an acid you use a strong base such as $\ce{NaOH}$. My question is; why you can't use a weak base for this purpose? Is it because the ...
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1answer
34 views

Calculate pKa for lipids

I would like to calculate $\mathrm{p}K_\mathrm{a}$ of lipid molecules using some software tools. I have tried ChemAxon and compared with ChemDraw professional 16.0 version they are mostly similar. I ...
0
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1answer
2k views

How to calculate pH of solution made of H3PO4 and Na3PO4? [closed]

I am unable to calculate the $\mathrm{pH}$ of a solution made of $\pu{0.1 M}$ $\ce{H3PO4}$ and $\pu{0.05 M}$ $\ce{Na3PO4}$. How to set the approximation and which ions are present at the ...
0
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0answers
19 views

Why do alkaline breads bake browner/crustier?

Usually, when I bake bread there is only one leavening agent (either yeast or baking soda). However, today I tried a new recipe for cinnamon rolls that used yeast but then called for the addition of ...
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2answers
73 views

Which one is more acidic – 3,5-dinitrophenol or 4-nitrophenol

I’m confused because in 3,5-dinitrophenol, the inductive effect is dominating whereas in 4-nitrophenol the mesomeric effect dominates. So which one should we consider for acidity?
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2answers
559 views

Why would red fuming nitric acid become white fuming nitric acid if left out at low temperature?

I'm reading this answer which refers to both red fuming nitric acid (RFNA) and white fuming nitric acid (WFNA). Those two Wikipedia articles say: Red fuming nitric acid (RFNA) is a storable ...
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2answers
70 views

Why ammonium hydroxide precipitates metal salts?

When I was going through the chapter on pnicotgens, I got to know that ammonia acts as a Lewis base and it dissociates in water giving out hydroxide ion and the further hydroxide of ammonia, which we ...