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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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Ortho-effect in substituted aromatic acids and bases

When comparing o,m,p-toluidine basicities, the ortho effect is believed to explain why o-toluidine is weaker. But when comparing o,m,p-toluic acid basicities, the ortho effect is stated as a reason ...
user4114's user avatar
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10 votes
3 answers
12k views

How to set up equation for buffer reaction?

For buffer equations, how can you tell what to react with water? For example, if I have a 1 M acetic acid solution and 1 M sodium acetate solution (a conjugate acid-base pair) mixed together and am ...
user35532's user avatar
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24 votes
2 answers
7k views

Is HF the least acidic hydrogen halide?

Fluorine is the most electronegative halogen and therefore, there is larger difference in electronegativity between the atoms of $\ce{HF}$ than any other hydrogen halide, which means the positive ...
Apoorv's user avatar
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15 votes
1 answer
8k views

Calculating the pH of a highly dilute solution of HCl

For relatively high concentrations of $\ce{HCl}$, I usually just assume that $[\ce{H+}] = [\ce{HCl}]$, because $\ce{HCl}$ is a strong acid and is completely ionized in solution. By taking the negative ...
QCD_IS_GOOD's user avatar
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20 votes
1 answer
19k views

Relative acidities of alkanes, alkenes, and alkynes

How does one explain the trend in bond lengths and acidity of the following hydrocarbons? $$\begin{array}{ccc} \hline \text{Species} & \ce{C-H}\text{ bond length / Å} & \mathrm{p}K_\mathrm{a} ...
tkhanna42's user avatar
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45 votes
4 answers
53k views

The reason behind the steep rise in pH in the acid base titration curve

Most books refer to a steep rise in pH when a titration reaches the equivalence point. However, I do not understand why … I mean I am adding the same drops of acid to the alkali but just as I near the ...
Eliza's user avatar
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34 votes
4 answers
67k views

What's the difference between a nucleophile and a base?

Obviously it depends on the context whether you would call a particular species a nucleophile or a base but are the two terms largely synonymous or is there a difference?
RobChem's user avatar
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125 votes
7 answers
87k views

Is a negative pH level physically possible?

A friend of mine was looking over the definition of pH and was wondering if it is possible to have a negative pH. From the equation below, it certainly seems mathematically possible—if you have a $1.1$...
apnorton's user avatar
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18 votes
2 answers
11k views

How should the hydrated proton be represented in chemical equations?

I learned the equation $$\ce{H2O + H+ -> H3O+}$$ And I know $\ce{H+}$ and $\ce{H3O+}$ really mean the same thing. But I am confused as to when I should use $\ce{H+}$ and when I should use $\ce{...
Simon-Nail-It's user avatar
41 votes
3 answers
34k views

Is methanol more acidic than water?

Methanol is slightly more acidic than water. Their $\mathrm{p}K_\mathrm{a}$ values, in water, are $15.5$ and $15.7$, respectively. All other aliphatic alcohols, however, are less acidic than water. ...
Dissenter's user avatar
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26 votes
4 answers
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Why is acetic acid more acidic than phenol?

Acetic acid (ethanoic acid, $\mathrm pK_\mathrm a \approx 5$) is more acidic than phenol ($\mathrm pK_\mathrm a \approx 10$), which is reflected in their reactivity with a weak base such as sodium ...
Manisha Poudel's user avatar
12 votes
1 answer
2k views

Hydrogen halide acidity

Why is it that $$\mathrm{p}K_\mathrm{a}(\ce{HF}) < \mathrm{p}K_\mathrm{a}(\ce{HCl}) < \mathrm{p}K_\mathrm{a}(\ce{HBr}) < \mathrm{p}K_\mathrm{a}(\ce{HI}),$$ even though the electronegativity ...
Jori's user avatar
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41 votes
2 answers
10k views

Why is arsenous acid denoted H3AsO3?

Inspired by this question, I'm wondering why arsenous acid is frequently denoted $\ce{H3AsO3}$, as opposed to $\ce{As(OH)3}$, which would appear to more accurately reflect its connectivity? [edit] I ...
Richard Terrett's user avatar
32 votes
2 answers
35k views

What is the pKa of the hydronium, or oxonium, ion (H3O+)?

Although the wikipedia page on Hydronium indicates a $\mathrm{p}K_\text{a}$ of −1.74, I noticed in the discussion of this page that the subject seems debated (cf. http://en.wikipedia.org/wiki/Talk:...
The Quark's user avatar
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25 votes
3 answers
196k views

How does one tell if a specific molecule is acidic or basic?

Let's take the $\ce{KOH}$ molecule into account. I know it is a base from literature, but how would one go about determining if a molecule is acidic or basic simply based on the structure of the ...
2567655222's user avatar
-1 votes
2 answers
1k views

Calculate pH of a mixture of a strong base and acid. Knowing only the pH, wt/v%, and volume of both solution. [closed]

Title explains all. I have been stuck on this for an hour and for some reason cannot understand it. I have tried to do an ICE table but get stuck halfway as I do not know whether I would use the w/v ...
Oliver A.'s user avatar
9 votes
4 answers
4k views

Why does the inverse relationship between the strengths of an acid and its conjugate base appear to be violated in the case of chloric(I) acid?

Hypochlorous acid is a weak acid with $\mathrm{p}K_\mathrm{a}(\ce{HClO}) = 7.53$. Then why is its conjugate base, $\ce{ClO-}$, a weak base in water? Shouldn't the strength of the base be inversely ...
asdf's user avatar
  • 205
9 votes
3 answers
6k views

The pH of a neutralized solution

If pH is defined as the concentration of hydrogen ions in solution, then how can a ‘neutralized’ solution (defined as having an equal amount of hydrogen and hydroxide ions) have a pH other than 7? ...
ahorn's user avatar
  • 209
6 votes
2 answers
5k views

Ammonium Hydroxide Name

Why is an aqueous solution of $\ce{NH3}$ (ammonia) often referred to as $\ce{NH4OH}$? I know that dissolved ammonia gas reacts with water in the following equilibrium: $$\ce{NH3 + H2O <=> NH4+ +...
Yunfei Ma's user avatar
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24 votes
2 answers
10k views

Comparing acidities of substituted and aromatic carboxylic acids

When comparing the acidities of carboxylic acids, we primarily see the electropositivity of the carboxylic acid carbons, i.e. we see how effectively the negative charge on the carboxylate ion is ...
stochastic13's user avatar
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21 votes
3 answers
17k views

Does the number of H+ ions in solution go up on dilution of a weak acid?

In my textbook, a footnote says: In case of weak acids, on dilution the total number of $\ce{H^{+}}$ ions in solution increases because dissociation of the weak acid increases This didn't make ...
Gerard's user avatar
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15 votes
2 answers
17k views

What is the Ka of OH- and Kb of H3O+?

What is the $K_\mathrm{a}$ of $\ce{OH^-}$ and $K_\mathrm{b}$ of $\ce{H_3O^+}$? Have these constants been determined?
EJC's user avatar
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15 votes
1 answer
12k views

Why does hydrogen bonding in salicylic acid make it more acidic?

When salicylic acid deprotonates (losing the proton from the carboxyl group) it forms a hydrogen bond with between the oxygen in the carboxylate anion and the hydrogen in the alcohol group. However, ...
RobChem's user avatar
  • 9,802
13 votes
3 answers
9k views

How can the equilibrium shift, while Kc remains constant?

Consider the following reversible reaction. $$\ce{Cr2O7^2-(aq) + H2O(l) <=> 2 CrO4^2-(aq) + 2 H+(aq)}$$ What will happen to the position of equilibrium and the value of $K_c$ when more $\ce{H+}$ ...
DarkLightA's user avatar
10 votes
2 answers
26k views

Why is water not part of the equilibrium constant?

In the acid base reaction $$\ce{NH4+ + H2O <-> NH3 + H3O+}$$ the acidity constant, which is a relation between concentrations is given by $$K_{\mathrm{a}}=\frac {\ce{[NH3]} \cdot \ce{[H3O+]}}{...
YoussefDir's user avatar
8 votes
1 answer
6k 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{...
Meow's user avatar
  • 909
103 votes
7 answers
331k views

Is it actually possible to dispose of a body with hydrofluoric acid?

In the TV show "Breaking Bad", Walter White frequently gets rid of people who get in his way by submerging them in a plastic container full of hydrofluoric acid. This, at least in the TV show, ...
user avatar
29 votes
3 answers
11k views

Which molecule is more acidic: CHF3 or CHBr3?

I know that fluorine is more electronegative than bromine. However, because of the size of bromine, it is more stable with a negative charge. In the case of $\ce{HF}$ vs. $\ce{HBr}$, to me, $\ce{HBr}$ ...
George's user avatar
  • 291
13 votes
2 answers
10k views

Should bromine water be called a solution?

Bromine water is a reagent which is used to test for unsaturation in organic compound. It is $2.8~\%$ bromine in water. In many places, it is refer to as bromine solution. But it is observed that ...
Nilay Ghosh's user avatar
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2 votes
1 answer
941 views

How to determine the strongest oxyacid of chlorine?

Which is the strongest acid here? $\ce{HClO}$ $\ce{HClO2}$ $\ce{HClO3}$ $\ce{HClO4}$ I found this question, didn't really get the first answer, but this one in particular seemed interesting. ...
Saturn's user avatar
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22 votes
4 answers
8k views

Why do Organolithium or Grignard reagents act as nucleophiles and not as bases with aldehydes and ketones

I've read entire Chapter 14: Organometallic Compounds of Francis Carey's "Organic Chemistry" but I still didn't get an answer to my question. Quote from the book: Because of their basicity ...
claws's user avatar
  • 963
17 votes
1 answer
15k views

Is cyclopentadiene or cycloheptatriene more acidic?

Which of the following cyclic compounds are more acidic? The most acidic proton is positioned on the carbon that is at the top of the above drawings (the methylene hydrogens) on each of the two ...
RobChem's user avatar
  • 9,802
15 votes
4 answers
71k views

Shouldn't the pH at the equivalence point always be 7?

I learned in class that the equivalence point in an acid-base titration is reached when the solution contains an equal amount of substance of $\ce{OH-}$ and $\ce{H+}$ ions. However, in a weak acid and ...
Eliza's user avatar
  • 2,423
15 votes
2 answers
17k views

Is steric inhibition of resonance or steric inhibition of protonation dominant in o-toluidine?

I wish to know which effect out of steric inhibition of resonance (SIR) or steric inhibition of protonation (SIP) is dominant over the other when comparing basicities of o-toluidine and aniline: ...
Shrish Shankar's user avatar
15 votes
2 answers
2k views

How is volatility useful in the production of acids?

Sulfuric acid because of its low volatility can be used to manufacture more volatile acids from their corresponding salts. How does volatility affect the production of acids? Isn't it that sulfuric ...
JM97's user avatar
  • 3,487
13 votes
3 answers
3k views

pKa differences and reactivity

I know a lot of chemists like to quote $\mathrm{p}K_\mathrm{a}$ values and subtract them to reinforce some notion about some acid-base reaction being highly favorable or highly unfavorable or whatnot. ...
Dissenter's user avatar
  • 19k
11 votes
1 answer
5k views

Basicities of nitrogen atoms in purine

Arrange the sites in purine in order of basicity. I feel that 9 is the least basic as nitrogen's lone pair is delocalised. However, I am unable to rank 1, 3, and 7 in a particular order. Is there a ...
user488460's user avatar
9 votes
3 answers
6k views

Find the pH of an amphiprotic salt dissolved in water at room temperature

Let's say I have a polyprotic acid $\ce{H2A}$ with the following properties: $$ \begin{align} \ce{H2A &<=> HA- + H+} & K_1 &= 1\cdot 10^{-1}\\ \ce{HA- &<=> A^2-+ H+} & ...
Caelan Miron's user avatar
7 votes
3 answers
49k views

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 ...
user209347's user avatar
5 votes
2 answers
26k views

Why will a strong acid neutralize as much base as a weak acid?

This is a simple concept that I can't seem to understand. Why will a strong acid neutralize as much base as a weak acid, if the acids are of the same volume and concentration? A strong acid will ...
Skeleton Bow's user avatar
4 votes
2 answers
3k views

Are aromatic amines or amides less basic?

When the lone pair of an amino group $\ce{R-NH2}$ is involved in resonance, its basicity decreases. But, between conjugation with carbonyl group $\ce{R}=\ce{R'CO}$ or resonance with benzene $\ce{R} = \...
Rajath Radhakrishnan's user avatar
4 votes
3 answers
15k views

Protonation of Guanidine

Why is the $\ce{sp^2}$ hybridized nitrogen atom in guanidine the most basic? I know that as a general guideline, $\ce{sp^3}$ hybridized atoms are more basic than $\ce{sp^2}$. Bases are electron pair ...
Dissenter's user avatar
  • 19k
-2 votes
2 answers
2k views

Is Magnesium Oxide alkali [closed]

Given that Magnesium Hydroxide is an alkali, can we say Magnesium Oxide is an alkali since dissolving Magnesium Oxide in water can produce Magnesium Hydroxide?
Diamond Science's user avatar
60 votes
4 answers
246k views

Why add water first then acid?

From school, I remember a very important rule: first you need to pour the water and then the acid (when you need to mix them) not vice-versa. This is because otherwise the aсid becomes very hot and ...
pmod's user avatar
  • 1,053
35 votes
1 answer
59k views

Acidity of substituted phenols

Phenol has a $\mathrm pK_\mathrm a$ approximately equal to $9.9$. When one studies the acidity of chlorophenols, one notices the following: First of all, chlorophenols are more acidic than phenol, ...
mannaia's user avatar
  • 1,756
31 votes
3 answers
25k views

What is the strongest acid?

According to Wikipedia, $\ce{HeH+}$ and fluoroantimonic acid are the strongest. According to a News article in Nature, Carborane acid is the strongest, but Wikipedia says fluoroantimonic acid is ...
NeilRoy's user avatar
  • 1,683
23 votes
4 answers
14k views

What's the strongest known organic acid?

What's the strongest known organic acid? Is it maybe trifluoromethanesulfonic acid or tautomer of pentacyanocyclopentadiene? EDIT: Since the question was reactivated I thought about formalising it. I ...
Mithoron's user avatar
  • 4,606
20 votes
3 answers
11k views

Why is ammonium a weak acid if ammonia is a weak base?

$\ce{NH3}$ is a weak base so I would have expected $\ce{NH4+}$ to be a strong acid. I can't find a good explanation anywhere and am very confused. Since only a small proportion of $\ce{NH3}$ molecules ...
Clangorous Chimera's user avatar
17 votes
1 answer
17k views

How does the litmus pH indicator work?

I'm wondering about how does the litmus solution work as a pH indicator. And another question: When you put drops of litmus solution into an colorless acid (e.g. $\ce{HCl}$), it turns red. But then ...
hello all's user avatar
  • 391
14 votes
2 answers
169k views

What are the products of the dissociation of sodium bicarbonate in water? What is the relative pH of the solution?

I had a recent question on a test that asked what the products would be if sodium hydrogen carbonate were dissolved in water. I had a few candidate answers $\displaystyle\ce{NaHCO3 -> Na+ + HCO3-}$...
scrblnrd3's user avatar
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