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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How are Grignard reagents stable in an ethereal solution? [duplicate]

I have heard of the leveling effect, which mentions that highly basic ions cannot exist in a solvent if it's acidity is high enough to be deprotonated by the base. Considering that, check out the ...
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Buffer formation in weak acid/strong base titration?

I'm a little confused about what happens when you titrate a weak acid or base. For example, let's say that you are trying to titrate a weak acid. Based on this question, it seems like the weak acid ...
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2answers
710 views

Determining (approximately) the amount of a strong base needed to change a buffer's pH by a certain number of units

I'm measuring buffer capacity by titrating $\ce{NaOH}$ into a buffer of $\ce {H3PO4 + NaH2PO4}$. I'm measuring buffer capacity by recording the amount of $\ce{NaOH}$ required to increase the $\mathrm{...
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1answer
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Is it possible to create a 4 inch by 4 inch channel through concrete using acid?

I'm trying to figure out a way to eat through concrete without damage pex tubing inside (its a radiant heated slab). Is there any way using some type of acid (hydrofluoric, muriatic ) to eat a 4 inch ...
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Protonation of ketone and ester

If there is a ketone and ester functional group in the same compound and I want to protonate with $\ce{HCl}$, which one will protonate first? Is it the carbonyl group in the ketone or the carbonyl ...
6
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1answer
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Between ethene and propene which is more acidic and why?

Between ethene and propene, which is more acidic and why? If they are they are the same then why so? Their $\mathrm{p}K_{\mathrm{a}}$ is the same $\mathrm{p}K_{\mathrm{a}}$ as ~44.
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Alternative PCB etching solutions - Is KMnO4 or NaClO suitable oxidizer?

I need to etch small PCB for my project, since I do this once in a blue moon I would like to try some easy approach, preferably with household items. I'm aiming at the use of acetic acid with hydrogen ...
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Can you create a buffer with a strong acid?

So I was wading through several textbooks yesterday reviewing the concepts of buffers. I found them lot more challenging than I used to. One thing in particular disturbed me: The books and internet ...
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Is sulfide ion a stronger base than hydroxide ion?

I received these three responses. They are all, except the last response, incorrect to varying degrees. I am, however, unsure about how to grade these responses because the question itself, in my ...
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1answer
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Is there a relationship between pH indicator colors and the visible light spectrum?

When I examined the colors showed on a pH paper which is red for acids and violet for bases, greenish yellow for neutral and other ranges in between, I noticed that the sequence is exactly same to ...
6
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1answer
340 views

Timescale of Protonation and Deprotonation across micelle layers

I am curious about the timescales of protonation and deprotonation of solvent systems. As a followup, how is this affected when the proton source is separated by an organic phase? For instance, it is ...
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463 views

Comparing basic strength of nitrogen heterocycles

Compare the basic strength of the following compounds: d > b > c > a c > b > a > d c > a > b > d a > d > c > b I know that in compound (c), the π-bond between nitrogen and ...
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834 views

Steric inhibition of resonance vs. hydrogen bonding

I have to compare the acidic strength of these compounds: Now, in A and B hydrogen bonding will be present which will help stabilize the negative charge of the conjugate base. However, the hydroxyl ...
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Which method can be used to determine the pKa of an acid-base indicator like bromothymol blue?

I have a question about how one would determine the pKa of an acid-base indicator such as bromothymol blue. I know that spectrophotometric analysis is one option, but is it possible to perform an ...
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1answer
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How to find out pH of aquarium and apply it when adding HCl?

I'm trying to rescue a neglected fish tank. I've been trying to figure out how much extra hydrochloric acid to add to my water change for my fish tank to soften the water a little and reduce the pH a ...
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1answer
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Why is benzyl alcohol a slightly stronger acid than cyclohexanol?

Cyclohexanol has a pKa = 16, while benzyl alcohol has a pKa = 15.4 The given explanation is that the "polarity of the benzyl group stabilizes the negative charge on oxygen". My understanding is ...
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1answer
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“Carbon snakes” - what physico-chemical process causes the exothermic response?

Making a "carbon snake" requires the mixing of strong sulphuric acid with sugar, as explained in this about.chemistry webpage - the reaction causes rapid dehydration of the sugar and produces steam in ...
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1answer
371 views

How accurately does (pKa1 + pKa2) / 2 estimate the pH of an amphoteric salt?

This question came up when answering Find the pH and amphiprotic salt is added to water at room temperature. If we dissolve $\ce{NaHA}$ in water, the species $\ce{HA-}$ can act as acid or base: $$ \...
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1answer
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Site of first protonation of imidazole and aminoimidazole

I wish to ask where imidazole and aminoimidazole will be protonated on first protonation. Imidazole: Aminoimidazole: I suppose that the nitrogen (without hydrogen) of the ring is the most probable ...
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Relative acidity of p-chlorobenzoic acid and p-flurobenzoic acid

I want to compare the relative acidity of p-chlorobenzoic acid and p-flurobenzoic acid. Both of the facts below point to p-chlorobenzoic acid being more acidic: The carboxylic acid group is too far ...
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1answer
125 views

Determine the concentration of hydrogen cations to prevent precipitation of monocalcium phosphate?

Determine the $\ce{[H+]}$ needed to just prevent precipitation by $\ce{H2PO4-}$ in a $\pu{0.25 M}$ $\ce{H3PO4}$ solution that has $\ce{[Ca^2+]} = \pu{0.15 M}$. The $K_\mathrm{a1}$ of $\ce{H3PO4}$ is ...
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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 ...
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241 views

Dissolving Aspartic acid in vinegar?

I am trying to dissolve aspartic acid into vinegar as use as a carbon source in saltwater aquariums. It does not dissolve. I was told to increase the pH and it will work? What is the best way to ...
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1answer
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How is charge density a useful measure of polarising power and polarisability?

How do you use charge density ($Z/r$) as a measurement of polarising power and polarisability, and hence hard/soft acid character? So far I've been looking at different polarising power and ...
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Why isn't nitrous acid a product of nitrite and water?

Question Predict the products of the following acid-base reactions, and predict whether the equilibrium lies to the left or to the right of the equations $$\ce{NO2- + H2O -> ?}$$ I thought it ...
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Is there a reliable chemical theory that predicts pKa based on structure?

Obviously, there are general stability arguments that can be made to estimate relative pKas, such as evaluating the stability of the conjugate base of an acid, or thinking about how polarized the bond ...
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254 views

How does a 5th hydrogen bind to carbon atom in CH5[+]?

Can we bind a fifth hydrogen to a carbon atom if carbon is not in excited state? We have a big discussion in class and cannot clearly answer the question. If carbon atom excites an electron from $2\...
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Yellow precipitate in SnCl2 solution

I have a few small bottles of 0.5M $\ce{SnCl2}$ solution, however solution was prepared about 4 months ago, and there is a yellow precipitate on the bottom of each bottle. Working hypothesis is that ...
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431 views

Ligand strength - Coulombic effect and/or Electronegativities?

According to my teacher, these three Lewis bases generally decrease in strength in the following order: Ammonia Water Hydroxide ion I agree. However, he argues that their ability to act as Lewis ...
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3answers
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Acidic strength of para substituted benzoic acids

Comparing the acidic strength, the nitro-substituted group is definitely more acidic. This can be reasoned by fact that a higher delta positive charge which develops on the H due to the strong -M ...
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Why is lemon mixed with water considered alkalizing water?

The benefits and facts of alkaline water are often skewed due to the marketing of companies and uneducated hype for the innocent idea of unlimited potential. I wanted to know the specific reactions ...
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212 views

Why do different H+ in polyprotic acids have different K?

Why do different $\ce{H}$ atoms in a polyprotic acid have different values of $\pu{K_a}$? All $\ce{H}$ atoms (which can show acidic nature) have similar properties within the molecule. It does not ...
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3answers
6k views

Why is Ka constant when volume is increased?

The following graph shows $\ce{Ka}$ vs ${V}$ (Volume) at constant temperature, as ethanoic acid is diluted: However, I thought it would instead produce the following graph (see below). $\ce{Ka=[...
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Why is fluoroantimonic acid so strong?

I learned that all strong acids have a 100% degree of ionization and that there are no degrees of strength in acids; however, I also read that fluoroantimonic acid is 20 quintillion times stronger ...
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3answers
645 views

Can solid acids and bases have pH values? If not, how are they classified as acids or bases?

This answer states $\mathrm{pH}$ is the aqueous concentration of $\ce{H3O+}$ or $\ce{H+}$ ions in soution. I would not say that ice lacks $\ce{H3O+}$ and $\ce{OH-}$ ions as ice's structure would ...
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3answers
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What is the maximum molarity of aqueous HCl?

Here is a problem a made up: We have some aqueous $\ce{HCl}$. What is the maximum possible molarity of the $\ce{HCl}$? How do I solve this? I don't have any good ideas.
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pH range outside conventional 0-14 [duplicate]

Is a pH value outside 0 - 14 possible? I asked my teacher who said: yes, it is, but very difficult to achieve. Then on the internet, I found multiple answers, one saying it is but because of a fault ...
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4answers
751 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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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 ...
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2answers
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How to calculate Ka for hydronium and Kb for hydroxide? [duplicate]

I am wondering how to calculate the $K_a$ for hydronium, $H_3O^+$, and the $K_b$ for hydroxide. Because hydronium undergoes the equilibrium $\ce{H_3O^+(aq) + H_2O (l) <=> H_2O (l) + H_3O^+ (aq)...
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5answers
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What role does sulfuric acid play in the titration of oxalic acid and potassium permanganate?

The titration is between oxalic acid and potassium permanganate, with $\ce{H2SO4}$ added to oxalic acid. My question is what role other than a dehydrating agent and maybe catalysing does the $\ce{...
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2answers
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Solvent effects on acidity of ethanoic acid

Is ethanoic acid most acidic in DMSO, water or methanol? I suspect that the conjugate base would be most stabilized by a polar protic solvent (meaning it's weakest in DMSO), however, water and ...
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1answer
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Are all ionic compounds salts?

According to Wikipedia: A salt is an ionic compound that can be formed by the neutralization reaction of an acid and a base. Are all ionic compounds salts? Are all salts ionic compounds?
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Why doesn't Epsom salt dissolved in water act like sulfuric acid?

People take baths in it so it clearly doesn't. But if epsom salt is the salt of sulfuric acid when it dissolves the chemical ions present in sulfuric acid should also be present in the bath water and ...
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2answers
21k views

Electron withdrawing groups and acidity

I know that a strong electron withdrawing group reduces electron density and makes a molecule more acidic. Also, a meta substituent will have less effect than ortho and para substituence and the para ...
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3answers
152 views

Iterative method for calculating pH of a weak acid / base

The problem asks to determine the $[\ce{H+}]$ in a $0.20~\mathrm{M}$ solution of $\ce{Na3PO4}$. The $K_\mathrm{a}$ of $\ce{HPO4-}$ was given as $4.5\times 10^{-13}$, which then allows one to calculate ...
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10k views

Can any compound be a Lewis acid but not be a Brønsted acid?

Is it possible for a compound to act as a Lewis acid but NOT act as a Brønsted acid? When would this happen? Could you please give a few examples where/why this happens ?
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Why is water an Arrhenius acid?

Is water an Arrhenius acid? We define Arrhenius acidity with respect to water, but what will water itself be? It can donate $\ce{H+}$ as well as $\ce{OH-}$.
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3answers
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Reaction between NaOH and CO2

So I wanted to know what the reaction between sodium hydroxide and carbon dioxide can be, and upon research I got 2 answers. The first one is $$\ce{CO2 + NaOH(aq) -> NaHCO3(aq)}$$ and the second ...
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Does Cute Poison actually work?

For those of you that have watched Season 1 of Prison Break (TV Series), in the "Cute Poison" Episode Micheal Scofield combined $\ce{CuSO4}$ (Copper Sulfate) and $\ce{H3PO4}$ (Phosphoric Acid) to ...