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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Low-cost nontoxic corrosion inhibitor for steel exposed to hydrochloric acid

It seems that many commercial descaling solutions designed to remove scale (calcium carbonates, etc that form on water heaters) are a simple combination of an acid and an acid corrosion inhibitor for ...
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1answer
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Effects of Ka on the Half-Equivalence Point

I'm new to studying chemistry at a university level and am currently reviewing acid-base titrations. I am wondering about the relationship between your ionization constant for a weak acid ($K_\mathrm{...
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How to describe the ionization equilibria of multiple ionizable species

For a weak acid [PB] in a buffered solution [H2PO4]/[HPO4] at pH 7.5 where: If some of the species [PB] was removed from the solution by partitioning on to an adsorbent, the equilibrium of [PB] ...
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1answer
64 views

Are pKa values of acid and conjugate base the same?

When you look at $\mathrm{p}K_\mathrm{a}$ table, you can read $\mathrm{p}K_\mathrm{a}$ values of acids. Do conjugate bases also have $\mathrm{p}K_\mathrm{a}$ values? If both can have $\mathrm{p}K_\...
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54 views

Is the conjugate base of every polyprotic acid amphoteric?

Since all compounds with an accessable free lone pair can act as a Brønsted-Lowry base, I was wondering if there was any specific example of a substance that when it loses a proton, it cannot accept a ...
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605 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 ...
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1answer
37 views

I conducted some experiment and I want to know the resulting redish black thing

I placed two electrodes in a jar and poured the sparking water with lemon flavor. After about 5 hours, the water turned to blue and the negative probe had the redish black thing. I'd like to know what ...
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1answer
27 views

Is it stupid to put used acid into a pool after cleaning the chlorinator? [closed]

I have a salt pool, and when the chlorinator salts up with calcium, I clean it with a diluted acidic solution. What happens to the acidic solution after the reaction happens? I.e., does the pH change?...
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25 views

How to describe the enthalpy of acid dissociation in aqueous solutions?

How to describe the enthalpy of acid dissociation in aqueous solutions? If we had a weak acid "PB" that dissociates to give a proton and a conjugate base. Classically it would be described like the ...
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1answer
49 views

Drug pH and pKa known, is it an acid or a base? [closed]

I want to answer the question if a drug which is analysed for pH and pKa is ionised or not ionised in a cow stomach with a pH of 6. The drug has a pH of 8,52 and a pKa of 8,78. Since the pH is 8,52 ...
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211 views

Can ethylene glycol enhance the acidity of orthoboric acid?

My textbook says: Boric acid is a weak monobasic acid but on addition of certain organic polyhydroxy compounds, such as mannitol, glycerol, dextrose or invert sugar, it is transformed into a ...
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62 views

Saponification side reactions

When soap is made from triglycerides and NaOH reacting, is saponification the only reaction that occurs or are there other side reactions. Information concerning this issue seems slim online
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1answer
96 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 ...
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4answers
366 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 ...
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1answer
63 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 ...
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1answer
42 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, ...
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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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Solving Polyester but no chromed steel [closed]

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 ...
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1answer
37 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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38 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 ...
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2answers
67 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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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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1answer
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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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44 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
68 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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1answer
41 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 ...
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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
167 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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1answer
34 views

Error with explaination of shape of weak acid strong base titration?

I have read the other posts on the same question posted on chemistry exchange such as this one: Shape of Weak-Strong Acid-Base Titration and here : What does the small, steep curve at the very ...
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Should the tip of the burette of an automatic titrator be immersed in the analyte?

In all the tutorials I found online, the tip of the burette (containing the titrant - NaOH) was immersed into the analyte solution. My question is: shouldn't the tip be out of the solution? Isn't ...
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2answers
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What are the concentration changes when diluting an equimolar acetic acid: acetate buffer?

When a buffer (for example, a mixture of 100 mM acetic acid and 100 mM acetate), is diluted 10-fold, all the concentrations change drastically. Surprisingly, after re-establishment of equilibrium, the ...
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209 views

Equilibrium constant for the neutralization of weak acid by strong base

Acetic acid has a $K_\mathrm{a}$ of $\pu{1.8e-5}$. What is the equilibrium constant for the neutralization of this acid with $\ce{NaOH}$? Given acetic acid $$\ce{HC2H3O2 + H2O <=> C2H3O2- + ...
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1answer
36 views

Ranking basicity from a structure

I just came across this question in my revision. I selected (A) but the correct answer is (D). Could someone explain where I am going wrong? I is least stable --> most reactive --> most basic Cl is ...
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1answer
93 views

How is preparing a buffer possible?

I understand the concept of an equilibrium buffer solution, however I am a bit hung on how creating it doesn't shift the weak acid equilibrium. $$\ce{CH3COOH + H2O <=> CH3COO- + H3O+}$$ $$ K_\...
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Structure of pyrophosphorous acid

What is the structure of pyrophosphorous acid? I asked this question here because the answer which I found on web and other resources are inconsistent which each other. For example, following data is ...
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1answer
84 views

Conflicting definitions of Lewis acids

I have struggled in attaining a solid grasp of the Lewis acid/base concept largely because so many sources seem to offer conflicting definitions. For instance, Klein's Organic Chemistry mentions that ...
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1answer
203 views

Why Guanidine is called as strong base

I've studied pka of H2O as 15 and anything with a pka lower than it should be a acid . Guanidine has a pka of 13.8 and is being called as strong base . Why is it so. https://en.m.wikipedia.org/wiki/...
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1answer
164 views

Questions on Neutral oxides

Neutral oxides, are non metal oxides which are neither acidic nor basic. I have noticed a pattern for neutral oxides which I am unsure actually holds true. $\ce{CO}$, $\ce{H2O}$, $\ce{NO}$ and $\ce{...
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231 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 ...
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1answer
298 views

What alkali and alkaline earth metal oxides will turn moist red litmus blue and finally white? [closed]

How many of the following will turn moist red litmus blue and finally white? $\ce{Li2O}$, $\ce{KO3}$, $\ce{RbO2}$, $\ce{Cs2O2}$, $\ce{BeO}$, $\ce{MgO}$, $\ce{BaO2}$, $\ce{SrO}$. Since bleach ...
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2answers
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Wouldn't adding a proton acceptor still make a solution just as acidic?

Say if you add NH3 to a solution, and it accepts a proton, it still becomes NH4+ in a solution, which is also acidic. A base should decrease the hydrogen ion concentration in a solution, but how does ...
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1answer
35 views

Organic Layer/Aqueous Layer Question [closed]

I could not answer this question, it would be appreciated if someone could help.
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180 views

Is Fe(OH)2 soluble in alkalis?

I have just started inorganic chemistry in school and I have just learnt about metal aqua ions and how they react in water. I learnt that $\ce{[Fe(H2O)6]^2+}$ reacts in water by losing a $\ce{H+}$ ...
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1answer
74 views

How can I increase the viscosity of dilute hydrochloric acid

I'm cleaning the mortar off a new clinker brick wall. Walls actually. I hate this job. The builder told me to wash down the wall with weak HCl, leave it for a minute or two, and then spray it off with ...
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3answers
168 views

pH of 0.05 M NaH2PO3

What is the pH of a $\pu{0.050 M}$ solution of $\ce{NaH2PO3}$? I am given that $\mathrm{p}K_\mathrm{a1} = 2.0$ and $\mathrm{p}K_\mathrm{a2} = 6.58$. I am getting two different answers, $3.94$ and $4....
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51 views

Looking for experimental data for titration curves

I am looking for real, open source and free experimental dataset (not image, scan of table) of acid/base titration curves: pH versus titrant volume for many combination (strong/weak acid/base, ...
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1answer
421 views

Reaction between carboxylic acids and amines

Would some be able to explain why when I mix a carboxylic acid, like ethanoic acid, and an amine, say ethylamine, I get ethylammonium ethanoate. But when I mix a bi-functional group carboxylic acid (...
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Exceptionally weak basicity of pyridine [duplicate]

It is often explained that the relatively lower basicity of pyridine, relative to most amines, is due to the fact that the $\ce {N}$ lone pair resides in an $\ce {sp^2}$ hybridised orbital, instead of ...
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1answer
56 views

Acidity of carbonate ions creates paradox?

Whilst I understand why salts can be acidic or basic, the carbonate reaction confuses me (carbonate being a basic ion). $$\mathrm{{CO_3}^{2-} + H_2O \ce{<=>} {HCO_3}^- + OH^-} \\ \mathrm{{...
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1answer
79 views

Aromaticity fails?

Why is cyclopentadiene ($\mathrm{p}K_\mathrm{a} = 16$) less acidic than A) 2,4-pentanedione ($\mathrm{p}K_\mathrm{a} = 9$); B) phenol ($\mathrm{p}K_\mathrm{a} = 10$)? C) Even H20 (pka = 15.7) ...