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).

0
votes
0answers
72 views

What is the benefit of using a pH indicator reagent over pH strips or a meter?

I've recently started getting into chemistry a bit as a hobby. Nothing serious, just amateur level stuff mostly, primarily just to educate myself. Whenever I need to determine the pH level of a ...
1
vote
1answer
46 views

Dissociation behaviour of polyelectrolytes

Assuming a solution of 100 polycationic molecules, each of them carrying 100 amino groups and an apparent pKa of 6.5. Would it mean that, at a pH of 6.5, 50 molecules will be fully protonated 50 ...
1
vote
2answers
71 views

Which rate, the forward or reverse rate of acid dissociation, is more strongly affected when diluting acetic acid in aqueous solution?

Acetic acid is a weak acid. It is in equilibrium with acetate and hydronium ions in aqueous solution: $$\ce{CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)}$$ Ostwald's law states that the ...
1
vote
1answer
249 views

Reaction between NaOH and Carbonic acid

I was presented with the following reaction when we were just learning about acids and bases: $$\ce{2NaOH + H2CO3 -> H2O + Na2CO3}$$ however I had thought it might've been something like $$\ce{...
2
votes
1answer
69 views

Why degree of dissociation/ionisation affected by dilution? [closed]

What happens when we dilute, say, an acid which is weak, and then add water to it? What motivates or pushes it to dissociate more? We are just adding some molecules of water, right? So, what exactly ...
-1
votes
2answers
43 views

Can equilibrium be calculated at any time of an acid base reaction and still be the same? [closed]

Should the equilibrium constant $K$ be calculated at the end of an acid-base titration or can we calculate it in the middle of the titration for example? If so, will the calculated equilibrium ...
0
votes
2answers
268 views

What is the real pKa of water?

What is the $\text{p}K_\text{a}$ of water? A simple google search yields the value $15.74$, but this site and this paper say it's $14.0$. According to my understanding, the correct answer should be $...
0
votes
4answers
241 views

Is the titration of sodium carbonate with hydrochloric acid temperature dependent?

I am a chemistry teacher in a Cambridge school. In one of the titrations of sodium carbonate with HCl, there was one question asked: On heating the sodium carbonate solution before doing the ...
-1
votes
2answers
56 views

Methanol vs water. Acidic strength [duplicate]

Why $CH_3OH$ is more acidic than $H_2O$ while the same is opposite for other alcohols?
0
votes
2answers
97 views

How do dibromopyrazolones undergo base-promoted decomposition?

I was not sure but seeing the base as NaOH I used the fact that it will take most acidic hydrogen that is N-H and electron pair will come over it and it will resonate from two sides. I could make upto ...
-2
votes
2answers
259 views

Does diluting the titration flask change the molarity

I was solving the following problem on a test and I thought the answer was A, but the answer is actually D. Below is the problem and my reasoning: Answer choice B is clearly incorrect because the ...
0
votes
3answers
59 views

Solubility and pH

I was reading about antacids. It stated that in earlier times $\ce{NaHCO3}$ and a mixture of aluminium and magnesium hydroxide were used as antacids. In excess $\ce{NaHCO3}$ can make the medium ...
0
votes
2answers
201 views

Why is are weak acid-strong base and strong acid-weak base reactions irreversible?

In the case of both are strong, I can see why it's irreversible, because the acid is very willing to give a proton and the base is very willing to take one. Now here are my two main questions: In the ...
0
votes
1answer
96 views

How do I make a 0.5 M citrate buffer at pH 4.5?

I need to make a citrate-sodium citrate buffer at 0.5 M concentration and pH 4.5. I calculated the molarities of the citrate and disodium citrate based on the Henderson Hasselbalch equation, using a p�...
1
vote
1answer
87 views

Pale blue species forming during electrolysis of NaHCO3

I have a solution of 3500 ml $\ce{H2O}$ + 454 g $\ce{NaHCO3}$ in electrolysis at a potential of 12.5V using a lead anode and copper cathode. The surface areas aren't measured but they are enormous. I ...
1
vote
1answer
39 views

Acid value of linseed oil

For this we weigh $\pu{1.015 g}$ of linseed oil which is dissolved in alcohol. 3 drops of phenolphthalein (pH indicator) are added and a solution of potassium hydroxide of concentration $C = \pu{9.5e-...
2
votes
0answers
72 views

Confusion about prioritizing functional groups in case of poly functional organic compounds

According to Wikipedia, sulfonic acid $(\ce{-SO3H})$ is comparatively stronger than carboxylic acid $(\ce{-COOH})$. Then why is sulfonic acid lower in priority than carboxylic acid (while naming poly ...
1
vote
1answer
244 views

Can an iodine clock reaction work without using a strong acid?

I'm going to do an iodine clock reaction for a project and we had to submit the materials and safety sheets for the experiment a while ago. I thought I could do one by using hydrogen peroxide, sodium ...
1
vote
1answer
84 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
votes
1answer
26k views

Is Sulfuric hydrofluoric acid a real thing? [closed]

I saw a video on social media of a person disappearing into air when exposed to Sulfuric hydrofluoric acid vapours. I don't have much knowledge in chemistry. Is this possible combination.
0
votes
2answers
454 views

Acidic, Basic, and Neutral Medium

So I'm new to this concept and I can't find any proper explanation to this. What does it mean for a reaction to occur in an acidic, basic, or neutral medium?
2
votes
1answer
79 views

What are good examples of questions that make college students think about chemistry concepts? [closed]

I am teaching the second semester of general chemistry at the college level. The course tends to get bogged down in calculations, and sometimes we forget about the big picture and what is going on at ...
1
vote
2answers
151 views

Calculating dissociation degree from pH and Ka without given initial acid concentration

Is it possible to calculate the dissociation degree (DD) from pH and Ka without directly been given the initial acid concentration? I found the following formula: $$\text{DD} = \frac{K_\mathrm{a}}{...
0
votes
0answers
146 views

What is the maximum concentration of HNO3 (nitric acid) which may be handled outside of a hood?

Commercial stock solutions of HNO3 (nitric acid) are usually 70% w/w, and according to several MSDSs (e.g. here), it is dangerous to inhale it: Symptoms/effects after inhalation : Irritation ...
0
votes
2answers
521 views

Which of the following is the most acidic salt?

A 0.1 M solution of which salt is most acidic? (a) Aluminum(III) nitrate $\ce{Al(NO3)3}$; (b) Magnesium(II) bromide $\ce{MgBr2}$; (c) Sodium bicarbonate $\ce{NaHCO3}$; (d) Sodium formate $\...
14
votes
2answers
525 views

How can benzaldehyde have a pKa of 14.9?

There are numerous websites out there which claim that the pKa of benzaldehyde – C6H5CHO – is 14.90. (Just do a Google search for benzaldehyde pka to see what I ...
3
votes
1answer
80 views

“Don't pour oil into lye, pour lye into oil”

I was making soap last weekend and I got distracted, and thence I put too much lye into my oils blend. Basically, the whole soap paste is unusable to make soap because the cure will never be enough to ...
5
votes
2answers
376 views

Why can the acidic strength between H2S and HCl be explained on the basis of electronegativity but H2S and H2O can't?

Consider simply aqueous solutions of $\ce{H2S}$ and $\ce{HCl}$ . It is pretty much known that $\ce{HCl}$ is stronger than $\ce{H2S}$ in water. The reason behind that first is the electronegativity of ...
1
vote
0answers
131 views

Nucleophile vs base and Electrophile vs acid [closed]

How we will figure out that a given compound will behave as nucleophile or base ? Same problem for electrophile and acid. By the way I have already seen a similar question though I didn't find it ...
5
votes
3answers
132 views

Changes in pH when adding substances other than acids or bases

If I start out with 100 mM acetic acid, what substance (to a final concentration of 1 M) could I add to change the pH considerably? I was thinking of NaCl or ethanol or acetone. Substances added ...
2
votes
1answer
101 views

Acidic tendency of copper(II) ion vs. calcium(II) ion

In my Chemistry textbook, a table is shown wherein ions originating in various salts are categorised according to their acidic or basic tendencies. Among others, $\ce{Cu^2+}$ and $\ce{Ca^2+}$ are ...
1
vote
0answers
227 views

Why is C2H5 a stronger +I group than CH3?

While reading about the basic character of amines, I came across a note which said that $\ce{CH3-CH2-NH2}$ was more stable than $\ce{CH3-NH2}$ as $\ce{C2H5}$ was a stronger +I group than $\ce{CH3}$. ...
1
vote
0answers
29 views

Can an interaction be considered both hard-hard and soft-soft?

The $\ce {B-F}$ bond can be described as having both a large ionic and a large covalent character$\ce {^1}$, with the AIM charges on $\ce {F}$ and $\ce {B}$ being $\ce {-0.81}$ and $\ce {+2.43}$, ...
4
votes
1answer
266 views

Why are amidines more basic than amines?

Amidines can be thought of as carboxylic acid derivatives with the carbonyl oxygen replaced by a nitrogen and hydrogen atom; amidines exhibit conjugation. Amidines are more basic (less acidic) than ...
0
votes
2answers
71 views

How to balance this redox reaction taking place in a basic medium?

How to balance this reaction which is taking place in a basic medium? $$\ce{Al + MnO4- -> MnO2 + Al(OH)4-}$$ My Attempt Reduction half reaction: $$ \begin{align} \ce{4 H+ + MnO4- + 3 e- &-&...
2
votes
1answer
140 views

Molecular orbital explanation of why the protonation of the oxygen atom makes a carbonyl group more electrophilic

I was working on nucleophilic addition reactions to the carbonyl group (namely, hemiacetal formation) when I came across the following explanation for the use of acid catalyst and how it increases ...
0
votes
0answers
25 views

Which is more acidic 2-Ethylbenzoic acid or 2-Methylbenzoic acid?

Both will undergo Ortho effect But as ethyl group is more bulkier it will show more Ortho effect to -COOH group as compare to methyl Is the above reason is correct?
0
votes
2answers
98 views

Why Does 0.10 M Dihydrogen Phosphate Dissociate Rather than Hydrolyse in a Neutral Solution of Water?

Dihydrogen Phosphate has a Ka of 6.2x10^-8, yet it seems to form solutions with an acidic pH when it is in water. Why is that? Shouldn't it dissociate back to phosphoric acid and form a basic ...
1
vote
0answers
86 views

How do I neutralize 1.2 % muriatic acid (134.4 liters) residue with 99 % caustic soda flakes?

I cleaned my commercial water purification system with muriatic acid but I overdid it. Now there is excess muriatic acid residue. I used 6 liters of 29 % muriatic acid and further reduced with 33.6 ...
1
vote
0answers
58 views

Topic in Salt hydrolysis that I couldn't understand

Salts can be made up of all combination S of ( SA ,WA) and (SB , WB) I understand how to deal with salts of strong acids with both strong and weak bases and also of strong bases with weak and strong ...
0
votes
1answer
76 views

Water as a “Harmful Acid”

Apologies for the question which is far below the brilliance of the minds on this page. I have an A-Level in Organic Chemistry but I'm tying myself in knots with this one. I'm a magician looking to ...
1
vote
1answer
45 views

Why must a buffer solution contain both a weak acid and a salt solution of its conjugate base?

Doesn’t the weak acid dissociate to produce the conjugate base on its own? I understand that when a strong base is added to the buffer solution, the hydroxide ions will react with the hydrogen ions ...
2
votes
1answer
199 views

Acidity comparison between cyclopropene and cyclopropane

There many sources on the internet saying that cyclopropane is more acidic than cyclopropene because the conjugate base in latter would have antiaromaticity which would destabilize it. But in this ...
1
vote
0answers
34 views

Why aren't primidone's lactam groups acidic?

I understand that 5,5-disubstituated derivates of barbituric acid only show lactam-lactim tautomerism opposed to the lactim-lactam and keto-enol tautomerism of barbituric acid, hence the 5-mono and 5,...
1
vote
0answers
61 views

pKa Conceptual Questions [closed]

If anyone could clear up some of this conceptual confusion, that would be much appreciated. Is $\mathrm pK_\mathrm a$ an intrinsic property of a molecule? Or extrinsic? A property is extrinsic if it ...
5
votes
1answer
125 views

Using thermodynamics to predict the acid-base character of fluoride ion in water

I was working through the end-of-chapter exercises of the acid-base chapter in Shriver's Inorganic Chemistry when I came across the following problem: 4.7. The effective proton affinity $\ce{A^{'}_{...
0
votes
2answers
58 views

Does concentration or pKa define acid strength?

For example, is 3M HCl a stronger acid than 1M HCl? I would reason that the concentration of an acid/base does not influence its strength. Strength is determined by the pKa, and, as per Le Chatelier'...
2
votes
0answers
31 views

How to Separate Copper Nanowires in an Alumina Membrane

So, in my Chemistry Lab we had an experiment to use Whatman alumina membranes and GaIn eutectic to create Nickel nanowires through electrodeposition. So essentially Nickel wire electrode and alumina ...
-1
votes
1answer
29 views

If I add apple cider vinegar to a cleanser with a pH level of 7, will the pH level of it drop? [closed]

I am thinking about adding apple cider vinegar to my Physiogel Dermo cleanser which has the following ingredients: Aqua, PEG-75, Cetearyl Alcohol, Disodium Phosphate, Sodium Cocoyl Isethionate, ...
-1
votes
1answer
38 views

Quantity of base needed to neutralise litre of 36% HCl?

Sorry for asking a basic chemistry question. I last did this kind of chemistry at school about 30 years ago and I don't have confidence that I'd get it right from first principles :) Short version: ...