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).

Filter by
Sorted by
Tagged with
5
votes
3answers
162 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 ...
5
votes
2answers
4k views

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 $\ce{OH-}$.
5
votes
3answers
93k views

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 ...
5
votes
1answer
12k views

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 ...
5
votes
4answers
28k views

What is the pH of a 5M solution of hydrochloric acid?

What is the $\mathrm{pH}$ of a $\pu{5M}$ solution of hydrochloric acid? So in order to solve this, apparently all you need to do is plug it into the equation: $$\mathrm{pH} = -\log[\ce{H3O+}]$$ ...
5
votes
3answers
103k views

How do you explain pKa to non-professional?

Let's say we have substance $\ce{A}$, which is mixed with substance $\ce{B}$ to improve shelf-life because $\mathrm{p}K_\mathrm{a}$ of the substance $\ce{A}$ is $7.9$ and in mix the $\mathrm{pH}$ is $...
5
votes
1answer
71k views

Why is phenolphthalein an appropriate indicator for titration of a strong acid with a strong base?

How does the pH at the equivalence point, as well as the pH range over which the colour of phenolphthalein changes, make it a suitable indicator for titrations between strong acids and strong bases?
5
votes
1answer
5k views

Why do sodium halides react so differently with sulfuric acid?

Why do sodium halides react so differently with sulfuric acid? \begin{align} \ce{NaF + H2SO4 &-> NaHSO4 + HF} \tag{1a}\label{NaF}\\ \ce{NaCl + H2SO4 &-> NaHSO4 + HCl} \tag{...
5
votes
2answers
763 views

Calculate pH of a weak acid and weak base neutralization reaction

I'm an industrial pharmacist needing some help with some chemistry basics. I'm trying to calculate the theoretical pH of an effervescent preparation containing 2 mmol citric acid ($\ce{H3C6H5O7}$), 4 ...
5
votes
2answers
31k views

Why is a buffer solution best when pH = pKa i.e. when A-/HA=1

Buffers work best when $\mathrm{pH}$=$\mathrm{p}K_\mathrm{a}$ From the Henderson-Hasselbalch equation, $\mathrm{pH}= \mathrm{p}K_\mathrm{a} + \log_{10}\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)$ If $...
5
votes
2answers
2k views

Hydrogen bonding relating to molecular orbital theory

In [1, p. 232] here is an explanation of how alcohols hydrogen bond to each other and I do understand how the alcohols form hydrogen bonds to each other: FIGURE 6.15 Water and alcohols are ...
5
votes
2answers
3k views

pH of solution after adding SiCl4

Why is it that adding $\ce{SiCl4}$ will cause the pH of a solution to become acidic? I thought that only salts (ionic bonds break in water) can change the pH once dissolved in water. $\ce{SiCl4}$ has ...
5
votes
2answers
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 ...
5
votes
2answers
122 views

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 ...
5
votes
1answer
3k views

What is the pKa of methylamine

I completed a practice (not for marks) assignment for an organic chemistry course, and one of the questions asked for the pKa of methylamine. I looked on PubChem, and it gave a result of $10.6$. ...
5
votes
2answers
2k views

If the hydroxide ion is such a poor leaving group then why does water dissociate?

Water dissociates into the hydroxide and hydronium ions but, why does this happen if the hydroxide ion is such a poor leaving group. Alcohols don't undergo $\ce{S_{N}1}$ reactions because the ...
5
votes
3answers
3k 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 ...
5
votes
1answer
424 views

Why does the Lewis definition of acids specify a PAIR of electrons and not a single electron?

The Lewis definition of an acid is: "a compound or ionic species which can accept an electron pair from a donor compound." Why does it specify a pair of electrons and not just a single electron? I ...
5
votes
1answer
158 views

Is there any notion of pH out of solution?

For example, could one define a $\mathrm{pH}$ for pure acetic acid? It's a weak acid in water, but if someone handed you $1~\mathrm L$ of pure acetic acid, what would its $\mathrm{pH}$ be?
5
votes
1answer
1k views

How is NaOH able to clear a solution of Paraformaldehyde?

While making a solution of $4~\%$ para-formaldehyde for immunohistochemistry (to fix the tissue), we add para-formaldehyde into water and stir. It looks like a chalky supersaturated solution even ...
5
votes
1answer
2k views

The Acidity of the Hydrated Iron (III) Ion

Why is $\ce{Fe(OH_2)_6^{3+}}$ fairly acidic? This iron has six water molecules coordinated to it. In other words, water itself is a very weak acid. But when water is coordinated to iron, it becomes ...
5
votes
2answers
4k views

Does the hydrolysis speed increase when more H+ ions are in the solution?

In hydrolysis of polysaccharides, does the hydrolysis speed increase when more $\ce{H+}$ ions are present in the solution? So if I were to use $\ce{H2SO4}$ instead of $\ce{HCl}$ (same volumes) then $\...
5
votes
2answers
7k views

In aminobenzoic acid, do we have three different pKa's?

In para-aminobenzoic acid, how can I know whether the amino group loses a proton or not when $\mathrm{pH}$ exceeds $8.5$? I have only found two values for $\mathrm{p}K_\mathrm{a}$ but I never found ...
5
votes
2answers
706 views

What results from the reaction of pent-3-en-2-ol with hydrogen bromide?

I have seen the following reaction in my textbook: This was quite easy to understand, though I wonder why 2-bromopent-3-ene is not a possible result: Isn't this how $\ce{-OH^}$ groups and hydrogen ...
5
votes
2answers
518 views

Lemon Battery works on water?

My son and I were using a mini science experiment kit for creating batteries with copper, zinc, and lemonade, similar to the famous lemon battery project. My son's hypothesis was that the liquid had ...
5
votes
2answers
6k views

Why is the pKa of the thiol group in N-acetylcysteine higher then the pKa of the thiol group in cysteine?

I understand why cysteine has a $\mathrm pK_{\mathrm a}$ of 8.3. But the $\mathrm pK_{\mathrm a}$ of thiol in N-acetylcysteine is 9.27. Since there is an acetyl group attached to the nitrogen, doesn't ...
5
votes
3answers
11k views

Why does a weak acid and a salt containing its conjugate base form an acidic buffer?

I read this today: If you mix equal amounts of $1 M$ $\ce{H_3PO_4}$ and $1 M$ $\ce{NaH_2PO_4}$ you get a buffer at $pH<6$. The reason given is that a weak acid plus a salt containing the ...
5
votes
2answers
7k views

Why is formic acid considered an acid if it is a reducing agent?

My understanding was that since the acceptance of Lavoisier's revised Easter Memoir of 1778, all acids were understood to be oxidising agents.* However, formic acid is often listed as a reducing ...
5
votes
1answer
19k views

No indicator is suitable when titrating weak acid with weak alkali

This was a statement in my book: A solution of a weak acid cannot be titrated with a weak base using an indicator to find the end-point because the pH change is too gradual close to the equivalence ...
5
votes
1answer
2k views

The significance of the dissociation constant of an indicator

In the chapter acid-base, I learned about indicators and how they are actually weak acids. This is the equation given in our book: $\ce{HIn + H_2O <=> H_3O^+ + In^-}$ $K_{in}= \left(\frac{[\...
5
votes
2answers
12k views

Why is sulfuric acid used in crystallization

I read that: Take a cupful of water in a beaker and add a few drops of dilute sulfuric acid. Heat the water. When it starts boiling add copper sulfate powder slowly while stirring continuously. ...
5
votes
1answer
8k views

What's the technical term for supercharging an acid with an oxidizer? And does it always work?

In a recent Mythbusters episode, where they tested some Breaking Bad chemistry assertions, they debunked the hydrofluoric acid body-dissolving myth referenced elsewhere in Chemistry.SE in the question ...
5
votes
1answer
87 views

pKa of phenols using UV-Vis spectroscopy

I have done an experiment where I dissolved four different substituted phenols in acidic, basic, and buffer solutions, and recorded the UV-Vis spectra for each. I'm supposed to pick a wavelength where ...
5
votes
1answer
438 views

Does acid and base react directly, or do they react first with water?

If an acid $\ce{AH}$ reacts with a base $\ce{B}$ in aqueous solution, in textbook they write $$\ce{AH + B -> A- + BH+}\label{rxn:1}\tag{1}$$ But first I add acid to water and then base, so why ...
5
votes
1answer
262 views

Is the recipe for my shaving cream complete nonsense?

Preamble I have only basic education in Chemistry (excelled at Organic chemistry nomenclature, but then subsequently quit when I could not grok the simplest replacement reactions). Also I will note I ...
5
votes
1answer
933 views

In the bicarbonate ion, why can the hydrogen not bond to the carbon?

I've been studying electrophiles and nucleophiles recently, including how the carbonate ion ($\ce{CO3^2-}$) is stabilised through resonance. While drawing the model for bicarbonate, however, I ...
5
votes
2answers
2k views

Factors affecting strengths of carboxylic acids [closed]

For carboxylic acids, I read that electron-withdrawing groups like CF3 allow the anion resulting from dissociation to be more stabilized. However if CF3 is replaced with an electron-donating group ...
5
votes
1answer
1k views

pH of liquid hydrogen chloride vs hydrochloric acid

Is hydrogen chloride in liquid state acidic like hydrochloric acid? I know that hydrochloric acid is hydrogen chloride dissolved in water but I was wondering if liquid hydrogen chloride was also an ...
5
votes
2answers
2k views

pH of a buffer made with boric acid and potassium dihydrogen borate

The Problem Calculate the pH of a buffer that is $\pu{0.200M}$ $\ce{H3BO3}$ and $\pu{0.122M}$ $\ce{KH2BO3}$. The $K_\mathrm{a}$ for $\ce{H3BO3}$ is $7.3\times10^{-10}$ What I Tried For each of ...
5
votes
1answer
1k views

How to calculate the dissociation constant of a weak acid from the titration with a strong base?

Problem: A solution of an unknown weak acid of unknown concentration was titrated with a solution of a strong base of unknown concentration. During the titration, the pH after adding $\pu{2.00 mL}$ ...
5
votes
2answers
1k views

Why are oxyacids strong oxidizing agents?

I saw that all the oxyacids are strong oxidizing agent. I don't know why all the oxyacids are strong oxidizing agents? What is the reason?
5
votes
4answers
33k views

Sulfuric acid fumes from cleaning shower drain

This morning a workman came by to my newly rented property to fix a few things, among which a slightly blocked bathtub drain. He let some mild water run continuously and he poured down a chemical, ...
5
votes
1answer
330 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 ...
5
votes
1answer
27k views

Can acidified or neutral KMnO4 oxidise toluene to benzoic acid?

Why is alkaline $\ce{KMnO4}$ used in the oxidation of toluene to benzoic acid? Can acidified or neutral $\ce{KMnO4}$ be used in this conversion?
5
votes
1answer
363 views

Formation of carbonic acid from breath?

Is it possible that blowing on water (hot/cold) can cause a reaction between the $\ce{CO2}$ from expiration and the water, to form $\ce{H2CO3}$? Is $\ce{H2CO3}$ dangerous?
5
votes
3answers
2k views

Computation of pH when an acid and base are mixed in solution

I'm doing a basic chemistry course, and we are currently learning how to compute $\text{pH}$ from the acid dissociation constant (using $\left[\text{H}^{+}_{(\text{aq})}\right]=\sqrt{K_{a}\left[\text{...
5
votes
3answers
443 views

How to identify the most stable Lewis adduct of boron trichloride?

Which of the following is the most stable Lewis acid–base adduct? (a) $\ce{H2O\bond{->}BCl3}$ (b) $\ce{H2S\bond{->}BCl3}$ (c) $\ce{H3N\bond{->}BCl3}$ (d) $\ce{H3P\bond{->}BCl3}$ ...
5
votes
1answer
1k views

Comparing the basicity of benzamide and acetamide

What if we were asked to compare the basicity of benzamide and acetamide? Which one of them would be more basic? I read somewhere on the internet that benzamide must be more basic than acetamide due ...
5
votes
1answer
759 views

Classifying acid-base reaction between aluminium hydride and lithium hydride

So I was dealing with a reaction the other day, which is also briefly written in the title: $$\ce{AlH3(s) + LiH(aq) -> Li+(aq) + AlH4-(aq)}$$ The strange thing is: Arrhenius definition cannot ...
5
votes
1answer
5k views

How does a Lewis acid differ from an oxidizing agent; Lewis bases from reducing agents?

A Lewis acid is defined as an electron acceptor. An oxidizing agent is also defined as an electron acceptor (in the electronic theory of oxidation). So then what is the basic difference between an ...