Greg E.
  • Member for 9 years, 6 months
  • Last seen more than 6 years ago
  • Michigan
7 answers
113 votes
69k views
Is a negative pH level physically possible?
93 votes

It's certainly possible theoretically. Solve for $\ce{pH < 0}$: $\ce{-log[H+] < 0\\ log[H+] > 0\\ [H+] > 1}$ So, as you said, a solution in which the hydrogen ion concentration exceeds ...

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4 answers
18 votes
51k views
How much can the pH change through dilution?
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26 votes

Water undergoes autoionization, i.e., it reacts as follows: $$ \ce{H2O + H2O <=> H3O+ + OH-} $$ The equilibrium constant for this reaction at standard conditions is $K_w = [\ce{H3O+}][\ce{OH-}]...

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5 answers
44 votes
131k views
Difference between thermodynamic and kinetic stability
22 votes

Kinetics deals with all things that impact the rate at which a reaction occurs. One implication of that is that reaction kinetics are partially a function of the stability of the intermediate species (...

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3 answers
16 votes
7k views
Why is magic acid a superacid?
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21 votes

The explanation is that sufficiently strong Lewis acids like $\ce{SbF5}$ will form adducts even with very weak, traditionally non-coordinating Lewis bases like $\ce{SO3F-}$. The resulting anionic ...

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3 answers
27 votes
28k views
Why do salts such as NaCl dissolve?
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21 votes

As it happens, the enthalpy of solution of $\ce{NaCl}$ in water (that is, the energy change associated with the dissolution of sodium chloride crystals in water) at standard conditions is very ...

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2 answers
22 votes
10k views
Comparing acidities of substituted and aromatic carboxylic acids
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19 votes

In the case of 3-chloropropanoic acid vs. formic acid, I suspect the disparity in expected acidity can mostly be explained by solvation effects. The 3-chloropropanoic acid is much bulkier than formic ...

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1 answers
19 votes
9k views
Why are the halogens good disinfectants?
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17 votes

The halogens, particularly in their diatomic free states and within various oxoacids, are strong oxidizing agents by virtue of their high electronegativities, electron affinities, and reduction ...

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3 answers
25 votes
12k views
The acidity of boric acid
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16 votes

I think your suppositions and observations are basically correct. On the basis of general principles, it is certainly possible to imagine that such a mechanism might be at play. If one considers the ...

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2 answers
18 votes
4k views
Designing a theoretical synthesis of methamphetamine from phenylpropyne
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16 votes

I think the synthetic route you've proposed is quite good for the most part. However, I think your use of $\ce{NaH}$ to remove the tosylate is incorrect. $\ce{NaH}$ is a very strong base, but not a ...

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1 answers
8 votes
2k views
Does knowing the ratio of masses of the elements in a compound lead to the unique chemical identity of the compound?
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16 votes

No, knowing the mass ratios is not sufficient by itself. In the absence of additional information (for example, molar mass) that would only be enough information to determine the empirical formula, ...

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1 answers
9 votes
15k views
How do equilibrium shifts affect solids?
14 votes

When a particular chemical process is at equilibrium, the respective rates of the forward and backward reactions are equal, meaning that no net change in the concentrations of products and reactants ...

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2 answers
23 votes
9k views
What does lowercase r-s notation mean?
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13 votes

This notation is used to designate so-called "pseudoasymmetric carbons." This occurs in instances in which precisely two of the groups bonded to a tetrahedral carbon are structurally indistinguishable ...

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2 answers
20 votes
2k views
How do the molecules know the future? How do they proceed to form "Most Stable" compound?
13 votes

Clearly, molecules are not in any sense volitional agents. They're simply subject to the basic and immutable laws of thermodynamics, the second of which states that any isolated system always ...

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2 answers
5 votes
10k views
How many electrons can an orbital of type f hold?
12 votes

You're correct that there are seven possible spatial orientations for an f-type orbital, and hence seven possible orbitals in one f-type sub-shell. However, the question specifically asks for the ...

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1 answers
10 votes
3k views
How does toluene react at higher temperatures and why?
12 votes

Assuming you're talking about Friedel-Crafts alkylation of toluene, this can be explained by the reaction being reversible and thermodynamic control taking precedence at sufficiently high temperatures....

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2 answers
11 votes
45k views
What chemicals are in tap water that gives it a slightly basic pH level
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12 votes

The tap water is likely "hard," i.e., contains some dissolved mineral salts, most likely (primarily) calcium and magnesium carbonates and bicarbonates. The anions of these salts are slightly basic, ...

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1 answers
7 votes
8k views
Are there any amphoteric substances other than water and ammonia?
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11 votes

First, it may be worth elucidating the nomenclature a bit and distinguishing between amphiprotic and amphoteric substances. The former are those that can react as either acids or bases in the ...

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1 answers
4 votes
7k views
Why is cyclopentyne unstable?
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11 votes

Stable alkynes are normally linear, that is, they have bond bond angles of 180°. That is necessitated by the fact that alkynes are formed by two π-bonds and one σ-bond, which must be mutually ...

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4 answers
12 votes
76k views
Is sulfuric acid or hydrochloric acid stronger?
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11 votes

When using $\mathrm{p}K_\mathrm{a}$, one typically does not consider multiple dissociations for polyprotic acids, as the acidity of the conjugate base ($\ce{HSO4-}$ in the case of sulfuric acid) can ...

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1 answers
14 votes
391 views
Why do some solutions eventually stop boiling and start "popping" as they get more concentrated?
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11 votes

What you witnessed was probably something similar to superheating/bumping. Essentially, when a solution is heated too rapidly, large pockets of vapor can form beneath the surface of the liquid that ...

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3 answers
8 votes
8k views
Law of Multiple Proportions: What is the significance of small whole numbers?
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10 votes

There's no universally accepted hard cut-off, as far as I'm aware, which determines the range of numbers that would constitute "small" mass ratios. Generally, all textbook examples select compounds ...

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1 answers
11 votes
5k views
Why does water favour nucleophilic substitution over elimination?
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10 votes

The nature of the substrate (in particular the degree of substitution of the α-carbon) is of principal importance in determining which mechanism predominates. Generally, $\mathrm{S_N1}$ and $\mathrm{...

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1 answers
4 votes
3k views
What is the exothermic reaction of superglue with cardboard?
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10 votes

I believe this is due to the fact that cyanoacrylates polymerize by anionic (or sufficiently strong neutral nucleophile) addition. In particular, they react with hydroxyl ($\ce{-OH}$) groups; paper, ...

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2 answers
5 votes
6k views
Can substituted acetone undergo Cannizzaro reaction?
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10 votes

As far as I'm aware, the Cannizzaro reaction can't occur with ketones, only aldehydes. The reaction mechanism involves the transfer of hydride from the former carbonyl carbon (of the tetrahedral ...

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3 answers
5 votes
917 views
Can a polymer have different resonance structures?
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10 votes

There's no reason why the structural subunits of polymers could not exhibit resonance, provided there are conjugated $\pi$-bonds present. A polymer such as kevlar, for example, certainly benefits from ...

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2 answers
12 votes
8k views
Does unsubstituted benzoic acid not show resonance due to steric effects?
9 votes

I have never heard of this effect occurring with an ordinary, unsubstituted benzoic acid. There is, however, a phenomenon known as the ortho effect that occurs when bulky groups occupy the ortho ...

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1 answers
10 votes
3k views
What is C2H5-O-CH=CH2?
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9 votes

The particular reaction is of acetylene ($\ce{C2H2}$) and ethanol ($\ce{C2H5OH}$) to yield ethyl vinyl ether (IUPAC name ethoxyethene). It's one example of Reppe chemistry, a fairly diverse set of ...

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6 answers
14 votes
26k views
Why is carbon dioxide nonpolar?
9 votes

The formula for the net dipole moment $\vec{\mu_{net}}$ of an overall neutral system of $n$ charged point particles is given by: $$ \vec{\mu_{net}} = \sum\limits_{i}^{n} q_i\vec{r_i} $$ where $q_i$ ...

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2 answers
5 votes
576 views
Shape Of Cetyl Alcohol
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9 votes

This is simply how the chemist chose to draw the molecule in that particular instance, and cetyl alcohol is formally regarded as a straight-chain molecule. Cetyl alcohol has all single bonds and no ...

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1 answers
6 votes
447 views
When are we justified in making assumptions in questions
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9 votes

You can make certain assumptions in these and similar problems because concentration of uniform substances (whether it's expressed as molarity, molality, mass density, or something else entirely) is ...

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