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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questions with no upvoted or accepted answers
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Why does saline have a pH of 5.5?
I am a physician and administer 0.9% NaCl in water ("normal saline") to patients frequently. The bag says it has a pH of 5.5 (compared to the human body of 7.4).
I am asking why the pH is so low. It ...
7
votes
1answer
474 views
Does phosphoric acid remove stainless steel electropolished layer?
Electropolished stainless steel has a high corrosion resistance due to the oxide film that is created during electropolishing. The film mainly consist of chromium(III) oxide.
Phosphoric acid is ...
6
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123 views
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 ...
6
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288 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 ...
6
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462 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 ...
5
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0answers
94 views
Why is there no effective alternative to metal salts in antiperspirants?
Metal salts, especially aluminum compounds are used in antiperspirants to prevent sweating. I found out aluminum chloride hexahydrate, which is found in most antiperspirants, undergoes an acid-base ...
5
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51 views
Why does my rainwater turn yellow if I increase the pH to 7?
My rainwater is colourless when collected, but if I add a small amount of sodium hydroxide to increase the pH to about 7, after a few days it goes yellow.
The colour change happens more quickly if I ...
5
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214 views
pKa of different sites of butanone
From what I can tell, deprotonation of the central hydrogen leads to the more thermodynamically stable product (most substituted double bond. i.e. most stabilization by hyperconjugation). Therefore, ...
5
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482 views
Which is the stronger base?
I would like to know which of the two is the stronger base, tri-(n-butyl)amine or tri-(tert-butyl)amine?
I feel that the one with tert-butyl would be stronger as the inductive effect of tert-butyl ...
5
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104 views
Is there a way to force C-protonation of an enolate?
In another question, I mentioned that O-protonation of an enolate followed by tautomerization may lead to increased amounts of the thermodynamic product over the kinetic product (when those are ...
5
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562 views
Is phosphorus trichloride really a stronger Lewis acid than antimony pentafluoride?
The following was a question from the ETS Chem GRE guide and apparently this was an actual question on an exam a few decades ago. Unfortunately, no explanation for the answer was given, and I couldn't ...
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37 views
acid strength: Periodic trends vs delocalisation, which one is more important
In 1st year chemistry questions, the concept of acid strength is often introduced to students including the 3 factors that provide a heuristic explanation for most of the common acids and conjugate ...
4
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217 views
Solubility of PbSO4
The solubility of $\ce{PbSO4(s)}$ increase with the addition of $\ce{H2SO4}.$ Why?
I don't quite understand this. When dissolving $\ce{PbSO4(s)}$ we get the equilibrium equation:
$$\ce{PbSO4(s) <=...
4
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0answers
76 views
Basicity af N containing aromatic species
Hello friends, I got struck in this interesting question on basicity. I am able to get different answers applying different methods.
In general, for these compounds we have to see the lone pair ...
4
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42 views
Naming convention for buffer solutions/systems
Is there an official naming convention to follow for buffer solutions/systems? I've noticed that the name of the buffer usually just follows the name of the salt (ex. sodium acetate buffer), but what ...
4
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691 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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308 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 ...
4
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2answers
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Comparing Acidic Strength of H3PO4 and H3AsO4
The $pKa$ values for H3AsO4 and H3PO4 are $2.30$ and $2.12$ which indicate that H3PO4 is a stronger acid compared to H3AsO4. I looked up their electronegativity values to find that they are almost the ...
4
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0answers
78 views
What metal is used to back this mirror?
My father is attempting to remove the mirror from a piece of glass. We stripped the black paint from the back and exposed the shiny surface with acetone. In the past he has been able to remove ...
4
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0answers
2k views
Why is o-fluorophenol a stronger acid than p-fluorophenol?
The $\mathrm{p}K_\mathrm{a}$ value of o-fluorophenol is $8.7$, while that of the p-fluorophenol is $9.9$. It's obvious that the inductive effect is more dominant at ortho-position, which results in a ...
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Can someone help me finish this reaction?
This question revolves around sodium percarbonate (https://en.m.wikipedia.org/wiki/Sodium_percarbonate) and its reaction with sulfuric acid.
I didn't find anything, so I tried assembling it myself.
...
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515 views
Why does the open circuit voltage of a battery decrease with increase in pH of electrolyte, but the voltage across a load increase?
I tested a cell which had aluminum sulfate as its anode electrolyte (12 grams aluminum in 50 mL water and a pH of 3.2), and potassium hydroxide as the cathode electrolyte (5 grams of KOH in 200 g of ...
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Collective term for acid/base; hydronium/hydroxide
When writing about acids and bases it would seem very natural for me to abstract the set of both acids and bases and have a single noun for them, instead of cumbersomly listing them both each time. ...
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Mechanism for reaction between hydrochloric acid and magnesium
Balanced equation:
$$\ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)}$$
However, Cl- is a spectator ion so the actual reaction equation is:
$$\ce{Mg + 2H+ -> Mg^2+ + H2}$$
Here is my proposed ...
4
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1answer
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Titanium in HF vs HCl
So we tried the reaction between Titanium metal with hydrochloric acid and hydrofluoric acid at a similar concentration. While boiling temperatures and constant heat over a long period of time are ...
3
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0answers
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Acidity comparison on R-PO3H2
Question
Compare the acidity $(K_\mathrm{a1})$ of the following three acids:
$\ce{H3PO4},$ $\ce{Ph-PO(OH)2}$ and $\ce{H3C-PO(OH)2}.$
Thoughts
These three acids are of type $\ce{R-PO3H2},$ where ...
3
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0answers
63 views
Common ion effect
Let $\ce{HA}$ ($x$ molar) be a strong electrolyte and $\ce{HB}$ ($c$ molar) — weak electrolyte. As $\ce{HA}$ is strong electrolyte, it dissociates completely:
$$
\begin{array}{lcc}
\ce{&HA &-&...
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176 views
Why AlCl3 more acidic than FeBr3?
In compounds with lone pairs or with charge it is easy to predict acidity of compounds but how to describe acidic nature of such ($\ce{FeBr3}$, $\ce{AlCl3}$) transition element compounds ?
3
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Acidity comparison of charged group 16 hydrides
March's Organic Chemistry (7th ed - page 337 under "Periodic Table Correlations" in chapter "Acids and Bases") states that:
$\ce{H3O+ > H3S+ > H3Se+}$ is the acidity order of these charged ...
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508 views
Why does the proton transfer from the oxygen to the nitrogen atom in imine formation not occur through an intramolecular process?
In my book Organic Chemistry by David Klein, 2nd edition, the book shows that the oxygen atom first takes a proton from an acid, then, the conjugate base of the acid takes a proton from the nitrogen ...
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108 views
One half of a nail is exposed to vinegar. Un-exposed half develops a brown film. What is it?
I have recently done an experiment for my chemistry EEI (Year 12) where we are testing what factors effect the rate of corrosion. I used vinegar (acetic acid) as one of the acids and Hydrochloric acid ...
3
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91 views
Is DNA a base inside the cell?
DNA is deoxyribonucleic acid because it has phosphate groups in every one of it's nucleotides.
However, in aqueous solutions protons will ionize, leaving phosphates alone as negative groups, i.e., ...
3
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0answers
32 views
Help with idea for an optical ph sensor
I am experimenting at home with the idea of making an optical ph sensor that can read the colour of ph indicator using photodiodes.
I am wondering if there is some kind of ion permeable membrane ...
3
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311 views
Enthalpy change of chromate-dichromate reaction
I am a uni study doing chemistry. I have taken a little bit in highschool before, but not in a while.
In a (nonassessed) practical, we have to predict how heating a chromate/dichromate solution:
$$\...
3
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134 views
Constructing a reactivity series, magnesium more reactive than sodium?
I reacted about $0.25 \,\mathrm{g}$ of magnesium, sodium and lithium in $20 \,\mathrm{ml}$ of $2 \,\mathrm{M} \,\ce{HCl}$ at room temperature. This was all done in a $100 \,\mathrm{mL}$ beaker.
I ...
3
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0answers
122 views
Material that acts as a “sponge” for sulfuric acid?
I would like help with a materials problem I am looking into that pertains to a product I would like to develop.
What I seek is some kind of substrate that acts like blotter paper does. Ideally, the ...
3
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46 views
Trouble understanding Bradford Assay
From what I understand, the Bradford reagent contains Coomassie Brilliant Blue in an acidic solution so both of the (sulfonic acid groups? I'm not sure if this is the correct name- I can't seem to ...
3
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103 views
Acid-Base Conjugate Pairs with multiple Products
Identify the acid-base conjugate pairs in the following reactions:
$$\ce{H_2SO_4 + HNO_3 <=> HSO_4^- + NO_2^+ + H_2O}$$
The obvious acid base conjugate pair is $\ce{H_2SO4}$ and $\ce{HSO_4^-}$...
3
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0answers
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Lassaigne's test for sulfur
The sodium fusion extract is acidified with acetic acid and lead acetate is added to it. A black precipitate of lead sulphide indicates the presence of sulphur.
What is the need for acidification of ...
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461 views
Why would the effect of fluoride ions Protecting egg shells from acid erosion vary with different acids?
I did an experiment reacting egg shells and acid. The egg shells were soaked in varying concentrations of fluoride and it is seen the rate of reaction between egg shells and acid decreases with higher ...
3
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192 views
Relative etch rates of nitric acid on metals and oxides
I am trying to either find or calculate the etch rate of nitric acid ($\ce{HNO3}$) for various different metals and oxides. The ones I am interested in are titanium ($\ce{Ti}$), zirconium ($\ce{Zr}$), ...
3
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40 views
Elimination with Amines
$\hspace{35 mm}$
ATTEMPT:
Since $\ce{Et3N}$ is a weak base and the carbon to which $\ce{Br}$ is attached is tertiary, we can rule out $\mathrm{E2}$ and $\mathrm{S_N2}.$ As we are providing heat, the ...
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Why anhydrous acetic acid is differentiating solvent?
Anhydrous acetic acid is differentiating solvent in which strong acids show different strength but water isn't. Why anhydrous acetic acid shows the strength of acids clearly, but water solvent cannot ...
3
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772 views
How are Pauling's rules applied to Nitric acid?
The Lewis structure of nitric acid is:
So, since Pauling's rule is $\mathrm{p}K_\mathrm{a}=8-5p$, where $p$ is the number of oxo groups, how is the rule applied in this instance? $p=1.5$? $p=2$?
3
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158 views
How to prevent Tin ions from precipitating as Tin(II,IV) Hydroxides
Alright, so Tin ions in most of it's salts have the propensity to form Tin(II,IV) Hydroxides and then precipitating out of aqueous solutions. What can I throw in the solutions to prevent this? Using ...
3
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0answers
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Purity of precipitate in selective precipitation
An aqueous effluent contains $12\ \mathrm{mol\ l^{-1}}$ $\ce{Cd^2+}$ and $10\ \mathrm{mol\ l^{-1}}$ $\ce{Mg^2+}$ as solution of nitrates. Current practice is use $\ce{NaOH}$ to selectively precipitate ...
3
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26 views
Dissolving Time Function for Concrete
So I was just exploring some ideas on my own and am having trouble analytically solving the following:
Let $D(n,m,T)$ be the time it takes to dissolve an n x n x n cube of concrete in m molar HcL at ...
3
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0answers
938 views
Rationalizing Acidities of Ammonium Ion and Hydronium Ion
Stumbled across this interesting practice problem in my organic textbook. I have a few reasons for why $\ce{H4N+}$ is less acidic than $\ce{H3O+}$.
1) Let’s assess conjugate stability first. ...
3
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1answer
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Find the concentration of the HCl solution when mixed with 1.265g of ACES-K+
$1.265\ \mathrm g$ of N-(2-acetamido)-2-aminoethanesulfonic acid potassium salt (ACES-K+, $M=220.29\ \mathrm{g/mol}$) is dissolved in $88.42\ \mathrm{mL}$ of water. $27.59\ \mathrm{mL}$ of $\ce{HCl}$ ...
